Influenza (flu)

What

Influenza is a common disease of the respiratory tract. It affects people of all ages.

Who

Annual influenza vaccination is recommended for everyone ≥6 months of age.

Influenza vaccination is particularly recommended for:

• children aged 6 months to <5 years
• adults aged ≥65 years
• Aboriginal and Torres Strait Islander people
• people with medical conditions that increase their risk of influenza
• homeless people
• pregnant women
• carers and household contacts of people in high-risk groups
• residents, staff and volunteers in aged care and long-term residential facilities
• commercial poultry and pork industry workers
• people who provide essential community services
• people who are travelling during influenza season

People with the following medical conditions have a higher risk of influenza:

• immunocompromising conditions, such as HIV, malignancy, functional or anatomical asplenia, and chronic steroid use
• receiving immuno-oncology therapy
• received a haematopoietic stem cell or solid organ transplant
• cardiac disease
• Down syndrome
• obesity
• chronic respiratory conditions
• chronic neurologic conditions
• chronic liver disease
• other chronic illnesses that need medical follow-up or hospitalisation
• long-term aspirin therapy in children (aged 6 months to 10 years)
• preterm infants (<37 weeks gestation)

How

People are recommended to receive influenza vaccine every year.

Most people should receive 1 dose of influenza vaccine each year. However, the following people should receive 2 doses, 4 weeks apart:

• children aged 6 months to <9 years receiving influenza vaccine for the first time
• people of any age receiving influenza vaccine for the first time after haematopoietic stem cell or solid organ transplant

The type of vaccine used depends on the person’s age:

• People aged 6 months to <65 years should receive quadrivalent influenza vaccine (QIV).
• People aged ≥65 years should receive one of the enhanced trivalent influenza vaccines (TIVs), but may receive QIV if the enhanced TIVs are unavailable.

Why

Influenza is the most common vaccine-preventable disease in Australia. Although it can be a mild disease, it can also cause very serious illness in otherwise healthy people. It can require hospitalisation and can cause death.

See Infographic. Vaccination for healthy ageing.

Influenza vaccines available in Australia

The Therapeutic Goods Administration website provides product information for each vaccine.

See also Vaccine information and Variations from product information for more details.

Always check annual seasonal influenza vaccine statements. Vaccines and age eligibility change from year to year.

Influenza vaccines can change from year to year with regard to:

• which vaccines are registered by the Therapeutic Goods Administration
• the indicated ages for each vaccine 

Always check annual seasonal influenza statements published by the Australian Technical Advisory Group on Immunisation on health.gov.au website and consult the product information for each vaccine.

Dose and route

Influenza vaccines available in Australia come in pre-filled syringes of:

• 0.25 mL, for children aged 6 months to <3 years 
• 0.5 mL, for children aged ≥3 years and adults 

Some 0.5 mL syringes have a graduated mark to indicate a 0.25 mL dose, if needed.

Shake the pre-filled syringe vigorously before injection. Influenza vaccines are preferably given by intramuscular injection. However, they may also be given subcutaneously. 

Doses for children <9 years of age

Children aged 6 months to <9 years receiving influenza vaccine for the first time need 2 doses at least 4 weeks apart. This maximises the immune response to the vaccine strains. 

Children who received 1 or more doses of trivalent or quadrivalent influenza vaccine in a previous season only need 1 dose of influenza vaccine in the current and future seasons. This is regardless of whether a trivalent or quadrivalent vaccine is used.^50,51

If a child aged 6 months to <3 years is inadvertently given a 0.5 mL dose of influenza vaccine, take no immediate action. A 0.5 mL dose of inactivated influenza vaccine is likely to be immunogenic in children <3 years of age, and is safe in this age group.^52,53 

If a child aged ≥3 years is inadvertently given a 0.25 mL dose of influenza vaccine, give an extra 0.25 mL immediately. If the child has already left the vaccination setting, they should receive a full age-appropriate dose (0.5 mL) as soon as they can return.

Follow standard recommendations when giving any extra dose(s) during the current or future seasons (see Table. Recommended doses of influenza vaccine by age group). 

Doses for children ≥9 years and adults

People aged ≥9 years need 1 dose of influenza vaccine every year, regardless of whether they have ever had influenza vaccine before.

If a child aged ≥3 years or an adult is inadvertently given a 0.25 mL dose of influenza vaccine, give an extra 0.25 mL immediately. If the person has already left the vaccination setting, they should receive a full age-appropriate dose (0.5 mL) as soon as they can return.

For adults aged ≥65 years who have already received a high-dose or an adjuvanted trivalent influenza vaccine in the current influenza season, an extra dose of quadrivalent influenza vaccine in the same season is not recommended, but is not contraindicated.

Similarly, if they have received quadrivalent influenza vaccine, an extra dose of either the high-dose or adjuvanted trivalent influenza vaccine in the same season is not recommended, but is not contraindicated.

Follow standard recommendations when giving any extra dose(s) during the current or future seasons (see Table. Recommended doses of influenza vaccine by age group).

Co-administration with other vaccines

People can receive inactivated influenza vaccines at the same time as any other vaccine, including: 

• 13vPCV (13-valent pneumococcal conjugate vaccine)
• pneumococcal polysaccharide vaccine
• zoster vaccine 
• all scheduled childhood vaccines

Children can receive 13vPCV and inactivated influenza vaccine at the same visit if they need both vaccines. However, there is a possible small increased risk of fever and febrile convulsions when children receive the vaccines at the same time, compared with receiving the vaccines separately. One study found that the risk was about 18 more cases per 100,000 doses in children aged 6 months to <5 years. The highest risk was 45 per 100,000 doses in children aged 16 months. This is a relatively small risk increase.⁵⁴

However, immunisation providers should:

• advise parents and carers of the possible risk
• provide the option of administering these 2 vaccines on separate days, with an interval of at least 3 days

See Contraindications and precautions and Pneumococcal disease.

Interchangeability of influenza vaccines

Different age-appropriate brands are interchangeable for people who need 2 doses of influenza vaccine in a single season (see Table. Recommended doses of influenza vaccine by age group).

Timing of influenza vaccination

Annual influenza vaccination is recommended before the influenza season starts. Influenza circulation usually peaks between June and September in most parts of Australia. However, influenza can occur year-round, especially in tropical areas.

People can receive influenza vaccine from the time the vaccine becomes available, typically in March or April. The exact timing can vary from year to year. 

Protection is expected to last for the whole season, but optimal protection is within the first 3–4 months after vaccination. Deferring vaccination to the beginning of winter may result in greater immunity later in the season, but may also result in missed opportunities for vaccination and lack of protection if the influenza season starts early.

Immunisation providers need to weigh up these factors for each person, and balance them with the challenge of vaccinating large numbers of people in a short time. 

Offer vaccination throughout the influenza season. It is never too late to vaccinate, because influenza can circulate all year. In particular, pregnant women and travellers can benefit from vaccination at any time of the year. 

Because of the high rate of influenza in the general population, vaccinating employees can result in workplace benefits such as increased productivity and reduced absenteeism.⁵⁵ Employers should consider the benefits of offering influenza vaccine in their workplace, particularly for occupations at higher risk of influenza. See Vaccination for people at occupational risk.

Children aged 6 months to <9 years who are receiving their 1st lifetime dose should receive the vaccine as soon as possible after it becomes available. This helps to ensure enough time to receive a 2nd dose (recommended ≥4 weeks later) before the influenza season starts.

Post-vaccination symptoms may mimic influenza infection. None of the influenza vaccines available in Australia contain live influenza viruses, so they cannot cause influenza.

Injection site reactions

Injection site reactions occur in more than 10% of people who receive standard trivalent influenza vaccine (TIV) intramuscularly. These include:

• induration
• swelling
• redness
• pain^65-67

Studies directly comparing inactivated trivalent and quadrivalent formulations in children and adults showed that the safety profiles were similar.^53,68-70

Systemic adverse events

1–10% of people who receive standard inactivated TIVs will develop:

• fever
• malaise
• myalgia^65-67,71-73

These adverse events may start a few hours after vaccination and may last for 1–2 days.^65,66,71 

Immediate adverse events following influenza vaccination are very rare. They can include hives, angioedema or anaphylaxis. These probably represent an allergic response to a residual component of the manufacturing process, most likely egg protein.^56,61

However, people with a history of anaphylaxis after eating eggs or a history of a severe allergic reaction after occupational exposure to egg protein may receive influenza vaccination after medical consultation.^56,61 See People with egg allergy in Contraindications and precautions.

Adverse events after high-dose and adjuvanted influenza vaccines

Clinical trials show a higher rate of injection site reactions in adults aged ≥65 years after receiving the high-dose and adjuvanted TIVs, compared with standard TIVs. 

Around 30% of people who received Fluzone High-Dose and Fluad reported injection site reactions, compared with around 20% of people who received standard TIV. Both groups reported similar rates (about 30%) of systemic reactions.^74,75

Rates of severe or serious adverse events do not increase after receiving either the high-dose or the adjuvanted vaccine. This has been shown in clinical trials and post-licensure surveillance studies.^75-79

High-dose and adjuvanted TIVs are only registered for use in people aged ≥65 years. These vaccines are not recommended in younger people. However, clinical trials in some younger populations and post-licensure safety data after a high-dose or adjuvanted vaccine was inadvertently given to younger people suggest a similar safety profile to that seen in people aged ≥65 years.^80-84

Fever and febrile convulsions in children aged <5 years 

In 2010, higher rates of fever and febrile convulsions were reported in children aged <5 years after influenza vaccination, especially in children aged <3 years.

Only the Seqirus (previously bioCSL) vaccines Fluvax and Fluvax Junior were associated with this side effect. After vaccination with Fluvax or Fluvax Junior, children <5 years of age had febrile convulsions at a rate of 4.4 per 1000 doses, compared with no such events reported among children who received an alternative vaccine in the same year.⁸⁵ 

The Fluvax and Fluvax Junior vaccines are no longer available in Australia.

Safety of influenza vaccine during pregnancy or breastfeeding

Influenza vaccine is safe to give during any stage of pregnancy or while breastfeeding for both the mother and her baby.^86-89 This is despite the product information for influenza vaccines listing pregnancy as a precaution. See Variations from product information.

Guillain–Barré syndrome 

In 1976, a small increased risk of Guillain–Barré syndrome (GBS) was associated with 1 influenza vaccine in the United States. Since then, close surveillance has shown that GBS occurs at a very low rate of up to 1 in 1 million doses of influenza vaccine.⁹⁰ A physician must diagnose GBS, because it is complex.

See also People with a history of Guillain–Barré syndrome in Precautions, and Uncommon and rare adverse events following immunisation in After vaccination.

Narcolepsy 

Narcolepsy (sudden sleeping illness) has been associated with AS03-adjuvanted pandemic influenza vaccines. This was mainly seen in the Scandinavian population, and affected children especially.^91-93 These vaccines were not used, and are not available, in Australia. 

The only registered adjuvanted influenza vaccine in Australia contains a different adjuvant (squalene-based MF59 oil-in-water emulsion adjuvant). Narcolepsy has not been associated with influenza vaccine containing MF59 adjuvant, although the number of subjects aged <20 years in these studies was limited.^94,95

Symptoms of influenza

Influenza virus infection causes a wide spectrum of disease. People may have: 

• no or minimal symptoms
• respiratory illness with systemic features
• multisystem complications and death from primary viral or secondary bacterial pneumonia

Symptoms in adults

Fever is an obvious sign of infection and peaks at the height of the systemic illness. Other symptoms are similar for influenza A and B viruses, and include: 

• malaise
• fever
• chills
• headache
• anorexia
• myalgia
• cough
• nasal discharge 
• sneezing

Symptoms in children

The clinical features of influenza in infants and children are similar to those in adults. However, children may have: 

• higher fevers
• febrile convulsions
• otitis media
• gastrointestinal symptoms¹⁰¹ 

Infection in young infants may be associated with more non-specific symptoms.^101,102

Complications of influenza

Complications of influenza include:

• acute bronchitis
• croup
• acute otitis media
• pneumonia (primary viral and secondary bacterial pneumonia)
• cardiovascular complications, including myocarditis and pericarditis
• post-infectious encephalitis
• Reye syndrome
• various haematological abnormalities

Secondary bacterial pneumonia is a common complication in people whose medical condition makes them vulnerable to influenza. These people are at high risk during epidemics, and may die of pneumonia or cardiac decompensation.

Secondary bacterial pneumonia is more common than primary viral pneumonia.

People at risk of severe disease from influenza

Severe disease from seasonal influenza is more likely in:

• older people
• infants
• Indigenous populations (Aboriginal and Torres Strait Islander people in Australia)
• people who have never been exposed to an antigenically related influenza virus
• people who are infected with a highly virulent viral strain
• people with chronic conditions, such as heart or lung disease, renal failure, diabetes and chronic neurologic conditions
• people who are immunocompromised
• people with class III obesity (BMI ≥40 kg per m²)
• pregnant women
• people who smoke

Severe disease may also occur in otherwise healthy children and young adults. Annual attack rates in the general community are typically 5–10%, but may be up to 20% in some years. In households and ‘closed’ populations, attack rates may be 2–3 times higher.^103,104 However, because asymptomatic or mild influenza illness is common and symptoms are non-specific, many influenza infections are not detected.

Infections due to influenza A (H3N2) strains are more likely to lead to severe morbidity and increased mortality than influenza B or seasonal influenza A (H1N1) strains.^96,105-107

Each year, the World Health Organization recommends the strains to be included in influenza vaccines based on global influenza epidemiology.¹²¹ The Australian Influenza Vaccine Committee uses this recommendation to determine the influenza virus composition of vaccines for use in Australia.¹²²

Influenza vaccines in Australia

All the influenza vaccines available in Australia are either split virion or subunit vaccines. They are prepared from purified inactivated influenza virus that has been cultivated in embryonated hens’ eggs.

Although these vaccines may contain traces of egg-derived protein (ovalbumin), they contain less than 1 μg of ovalbumin per dose. See also Contraindications and precautions, and Vaccinating people with a known egg allergy in Vaccination for people who have had an adverse event following immunisation.

Quadrivalent influenza vaccines

Inactivated quadrivalent influenza vaccines (QIVs) contain 4 influenza virus strains – 2 influenza A subtypes and 2 influenza B lineages. QIVs have been registered for use in Australia since 2014, and have been in widespread use since 2016. 

Trivalent influenza vaccines

Trivalent influenza vaccines (TIVs) have been used since the 1970s and contain 3 strains of influenza virus: 2 influenza A subtypes and 1 influenza B lineage The 3 strains included are the same as those contained in QIVs, which contain an additional influenza B lineage.

From 2018, 2 new formulations of TIVs (also known as ‘enhanced TIVs’) became available for use in adults aged ≥65 years only. One is a high-dose vaccine that contains 60 µg haemagglutinin per included virus strain per dose — this is 4 times the haemagglutinin content of standard TIVs. The other contains an adjuvant, MF59, and the standard 15 µg of haemagglutinin per strain per dose. Both vaccines are formulated to induce a greater immune response than standard TIVs.

Efficacy and effectiveness of influenza vaccines

The efficacy and effectiveness of influenza vaccines of similar composition depend on the:

• age and immunocompetence of the vaccine recipient
• degree of similarity between the virus strains in the vaccine and those circulating in the community^45,123-130 

QIVs and TIVs

The efficacy of QIVs was established on the basis of non-inferior immune responses compared with TIVs against the 3 strains common to both vaccines.

A systematic review estimated the efficacy of standard TIV to be 59% against laboratory-confirmed influenza in healthy adults <65 years old; this varies with influenza season.¹³¹ Based on studies comparing the immune response of QIVs and TIVs, the efficacy of QIVs is expected to be similar. In one season in the United States when the circulating and vaccine strains were well matched, QIVs were about 54% effective against laboratory-confirmed influenza.¹³²

QIVs protect against an extra influenza B lineage compared with TIVs. The benefit of this cannot be predicted for any influenza season, because it depends on factors such as:

• the proportion of circulating influenza viruses that is attributable to the influenza B lineage that is not in the TIV, which varies every year⁹⁷
• antigenic mismatch between vaccine and circulating strains
• cross-protection against non-vaccine B strains afforded by the strain in the TIV
• a person’s pre-existing immunity to the circulating strains of influenza 

Influenza vaccines in young children

Young children can receive influenza vaccine from 6 months of age. Because these children are immunologically naive to influenza, they need 2 doses of influenza vaccine when immunised for the first time. This maximises the immune response to all vaccine strains.^133,134 Vaccination against the additional influenza B lineage in QIVs is expected to be particularly beneficial for children, who are more likely to be immunologically naive to all strains of influenza.¹³⁵

Young children gain similar levels of protection as older children and adults. Vaccine effectiveness is approximately 65% against laboratory-confirmed influenza in children aged 6–59 months in a season when the vaccine and circulating strains are well matched.^136-141

TIVs in adults aged ≥65 years

Standard-dose TIVs

The efficacy of inactivated standard TIV is about 43% against influenza-like illness in people ≥65 years of age living in the community when virus circulation is high. However, there have been few randomised controlled trials of influenza vaccine in older people.⁸

In nursing home settings in people aged ≥65 years, TIV is: 

• approximately 45% effective for preventing hospitalisations due to influenza and pneumonia
• 60% effective against all-cause mortality⁸

Enhanced TIVs: high-dose and adjuvanted influenza vaccines

Standard-dose TIVs have lower effectiveness in people aged ≥65 years than in younger people. Because of this, ‘enhanced’ formulations were developed to increase the immune system’s response to the vaccine. These enhanced vaccines increase protection compared with standard-dose vaccines, especially against influenza A (H3N2), which is more common and severe in older people.^74,78

In a clinical trial, the TIV with greater haemagglutinin content (Fluzone High-Dose) was about 24% more efficacious against laboratory-confirmed influenza than standard TIV.⁷⁶ It was also about 2–36% more efficacious than standard TIV in reducing influenza-related deaths.¹⁴²

In a large post-licensure study of community-dwelling adults aged ≥65 years, the adjuvanted TIV (Fluad) was about 25% more effective in preventing hospitalisation from influenza or pneumonia than standard TIV.¹⁴³

It is important to note that these studies were conducted independently of each other in different influenza seasons, and had different study designs. It is therefore not possible to compare these estimates of vaccine efficacy or effectiveness.

Compared with QIVs, the potential for Fluzone High-Dose and Fluad to improve protection is balanced by the potential loss of protection against the 2nd influenza B lineage (conferred by QIVs). However, disease from influenza A H3 strains is more common and more severe in people aged ≥65 years. Therefore, in this age group, the potential extra protection provided by Fluzone High-Dose and Fluad against the strains included in the vaccine is likely to offset the loss of protection against the additional influenza B lineage found in the QIVs. 

Influenza vaccines in pregnant women

In pregnant women, standard TIV is: 

• approximately 50% effective in reducing laboratory-confirmed influenza 
• 65% effective against inpatient hospital admissions for acute respiratory illness^144,145 

Vaccinating pregnant women against influenza also protects their infants against laboratory-confirmed influenza. This is due to transplacental transfer of high-titre influenza-specific antibodies. A recent systematic review concluded that maternal influenza vaccination reduces laboratory-confirmed influenza in infants <6 months of age by about 48%.¹⁴⁶ The vaccine protects infants for up to 6 months after birth. 

Duration of immunity

Protection against influenza requires annual vaccination with a vaccine containing the most recent strains. Recent evidence suggests that protection after influenza vaccination may begin to wane after 3–4 months.^{133,134,139,147-150} Low levels of protection may last another year for some strains, if the prevalent circulating strain remains the same or if there is only minor antigenic drift.^45,130 

It is not clear whether repeated annual vaccination affects year-to-year vaccine effectiveness. An Australian study reported sustained or increased vaccine effectiveness against influenza A and B illness and hospitalisation, particularly among children aged 2–8 years who received influenza vaccine in previous seasons.¹⁵¹ Also, data collected over 6 influenza seasons show that annual influenza revaccination among older people who live in the community is associated with a 15% reduction in the risk of annual mortality compared with first-time vaccination.¹⁵² 

However, a few studies, mainly in the United States, suggest that influenza vaccines are not as effective if they are repeated year after year.^153,154

Despite conflicting opinion about the impact of repeated annual vaccination on vaccine effectiveness, vaccinated people are still better protected against influenza than unvaccinated people.

Laboratory-confirmed cases of influenza are notifiable in all states and territories in Australia.

The Communicable Diseases Network Australia national guidelines for influenza infection¹⁵⁶ have details about the management of influenza cases and contacts.

State and territory public health authorities can provide further advice about the public health management of influenza, including in residential care facilities.

1. Grohskopf LA, Sokolow LZ, Broder KR, et al. Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices – United States, 2016–17 influenza season. MMWR. Recommendations and Reports 2016;65(RR-5):1-54.
2. World Health Organization (WHO). Vaccines against influenza WHO position paper – November 2012. Weekly Epidemiological Record 2012;87:461-76.
3. Li-Kim-Moy J, Yin JK, Blyth CC, et al. Influenza hospitalizations in Australian children. Epidemiology and Infection 2017;145:1451-60.
4. Li-Kim-Moy J, Yin JK, Patel C, et al. Australian vaccine preventable disease epidemiological review series: influenza 2006 to 2015. Communicable Diseases Intelligence 2016;40:E482-95.
5. Izurieta HS, Thompson WW, Kramarz P, et al. Influenza and the rates of hospitalization for respiratory disease among infants and young children. New England Journal of Medicine 2000;342:232-9.
6. Coffin SE, Zaoutis TE, Rosenquist AB, et al. Incidence, complications, and risk factors for prolonged stay in children hospitalized with community-acquired influenza. Pediatrics 2007;119:740-8.
7. Ampofo K, Gesteland PH, Bender J, et al. Epidemiology, complications, and cost of hospitalization in children with laboratory-confirmed influenza infection. Pediatrics 2006;118:2409-17.
8. Jefferson T, Di Pietrantonj C, Al-Ansary LA, et al. Vaccines for preventing influenza in the elderly. Cochrane Database of Systematic Reviews 2010;(2):CD004876. doi:10.1002/14651858.CD004876.pub3.
9. Nokleby H, Nicoll A. Risk groups and other target groups – preliminary ECDC guidance for developing influenza vaccination recommendations for the season 2010–11. Eurosurveillance 2010;15(12):pii=19525.
10. Dao CN, Kamimoto L, Nowell M, et al. Adult hospitalizations for laboratory-positive influenza during the 2005–2006 through 2007–2008 seasons in the United States. Journal of Infectious Diseases 2010;202:881-8.
11. Fritz S, Mossdorf E, Durovic B, et al. Virosomal influenza-vaccine induced immunity in HIV-infected individuals with high versus low CD4⁺ T-cell counts: clues towards a rational vaccination strategy. AIDS 2010;24:2287-9.
12. Haller W, Buttery J, Laurie K, et al. Immune response to pandemic H1N1 2009 influenza A vaccination in pediatric liver transplant recipients. Liver Transplantation 2011;17:914-20.
13. Siriwardena AN, Gwini SM, Coupland CA. Influenza vaccination, pneumococcal vaccination and risk of acute myocardial infarction: matched case-control study. CMAJ Canadian Medical Association Journal 2010;182:1617-23.
14. Pérez-Padilla R, Fernández R, García-Sancho C, et al. Pandemic (H1N1) 2009 virus and Down syndrome patients. Emerging Infectious Diseases 2010;16:1312-4.
15. Ciszewski A. Why young healthy adults should become a target group for the influenza vaccination: a cardiologist's point of view [letter]. Vaccine 2008;26:4411-2.
16. Morgan OW, Bramley A, Fowlkes A, et al. Morbid obesity as a risk factor for hospitalization and death due to 2009 pandemic influenza A(H1N1) disease. PLoS One 2010;5(3):e9694.
17. Van Kerkhove MD, Vandemaele KA, Shinde V, et al. Risk factors for severe outcomes following 2009 influenza A (H1N1) infection: a global pooled analysis. PLoS Medicine 2011;8:e1001053.
18. Phung DT, Wang Z, Rutherford S, Huang C, Chu C. Body mass index and risk of pneumonia: a systematic review and meta-analysis. Obesity Reviews 2013;14:839-57.
19. Kok J, Blyth CC, Foo H, et al. Viral pneumonitis is increased in obese patients during the first wave of pandemic A(H1N1) 2009 virus. PLoS One 2013;8(2):e55631.
20. Louie JK, Acosta M, Samuel MC, et al. A novel risk factor for a novel virus: obesity and 2009 pandemic influenza A (H1N1). Clinical Infectious Diseases 2011;52:301-12.
21. González-Candelas F, Astray J, Alonso J, et al. Sociodemographic factors and clinical conditions associated to hospitalization in influenza A (H1N1) 2009 virus infected patients in Spain, 2009–2010. PLoS One 2012;7(3):e33139.
22. Dixon GA, Moore HC, Kelly H, et al. Lessons from the first year of the WAIVE study investigating the protective effect of influenza vaccine against laboratory-confirmed influenza in hospitalised children aged 6–59 months. Influenza and Other Respiratory Viruses 2010;4:231-4.
23. Poole P, Chacko EE, Wood-Baker R, Cates CJ. Influenza vaccine for patients with chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews 2006;(1):CD002733. doi:10.1002/14651858.CD002733.pub2.
24. Schembri S, Morant S, Winter JH, MacDonald TM. Influenza but not pneumococcal vaccination protects against all-cause mortality in patients with COPD. Thorax 2009;64:567-72.
25. Mertz D, Kim TH, Johnstone J, et al. Populations at risk for severe or complicated influenza illness: systematic review and meta-analysis. BMJ 2013;347:f5061.
26. Zhang PJ, Cao B, Li XL, et al. Risk factors for adult death due to 2009 pandemic influenza A (H1N1) virus infection: a 2151 severe and critical cases analysis. Chinese Medical Journal 2013;126:2222-8.
27. Allard R, Leclerc P, Tremblay C, Tannenbaum TN. Diabetes and the severity of pandemic influenza A (H1N1) infection. Diabetes Care 2010;33:1491-3.
28. Sullivan-Bolyai JZ, Corey L. Epidemiology of Reye syndrome. Epidemiologic Reviews 1981;3:1-26.
29. Glasgow JF. Reye's syndrome: the case for a causal link with aspirin. Drug Safety 2006;29:1111-21.
30. Gill PJ, Ashdown HF, Wang K, et al. Identification of children at risk of influenza-related complications in primary and ambulatory care: a systematic review and meta-analysis. The Lancet Respiratory Medicine 2015;3:139-49.
31. Paranjothy S, Dunstan F, Watkins WJ, et al. Gestational age, birth weight, and risk of respiratory hospital admission in childhood. Pediatrics 2013;132:e1562-9.
32. Irving WL, James DK, Stephenson T, et al. Influenza virus infection in the second and third trimesters of pregnancy: a clinical and seroepidemiological study. BJOG: An International Journal of Obstetrics and Gynaecology 2000;107:1282-9.
33. Zaman K, Roy E, Arifeen SE, et al. Effectiveness of maternal influenza immunization in mothers and infants. New England Journal of Medicine 2008;359:1555-64.
34. Mak TK, Mangtani P, Leese J, Watson JM, Pfeifer D. Influenza vaccination in pregnancy: current evidence and selected national policies. The Lancet Infectious Diseases 2008;8:44-52.
35. Black SB, Shinefield HR, France EK, et al. Effectiveness of influenza vaccine during pregnancy in preventing hospitalizations and outpatient visits for respiratory illness in pregnant women and their infants. American Journal of Perinatology 2004;21:333-9.
36. American College of Obstetricians and Gynecologists, Committee on Obstetric Practice. ACOG Committee Opinion No. 468: Influenza vaccination during pregnancy. Obstetrics and Gynecology 2010;116:1006-7.
37. MacDonald NE, Riley LE, Steinhoff MC. Influenza immunization in pregnancy. Obstetrics and Gynecology 2009;114:365-8.
38. Eick AA, Uyeki TM, Klimov A, et al. Maternal influenza vaccination and effect on influenza virus infection in young infants. Archives of Pediatrics and Adolescent Medicine 2011;165:104-11.
39. France EK, Smith-Ray R, McClure D, et al. Impact of maternal influenza vaccination during pregnancy on the incidence of acute respiratory illness visits among infants. Archives of Pediatrics and Adolescent Medicine 2006;160:1277-83.
40. Tamma PD, Steinhoff MC, Omer SB. Influenza infection and vaccination in pregnant women. Expert Review of Respiratory Medicine 2010;4:321-8.
41. Englund JA, Mbawuike IN, Hammill H, et al. Maternal immunization with influenza or tetanus toxoid vaccine for passive antibody protection in young infants. Journal of Infectious Diseases 1993;168:647-56.
42. Benowitz I, Esposito DB, Gracey KD, Shapiro ED, Vázquez M. Influenza vaccine given to pregnant women reduces hospitalization due to influenza in their infants. Clinical Infectious Diseases 2010;51:1355-61.
43. Poehling KA, Szilagyi PG, Staat MA, et al. Impact of maternal immunization on influenza hospitalizations in infants. American Journal of Obstetrics and Gynecology 2011;204(6 Suppl 1):S141-8.
44. Savulescu C, Valenciano M, de Mateo S, Larrauri A, cycEVA Study Team. Estimating the influenza vaccine effectiveness in elderly on a yearly basis using the Spanish influenza surveillance network – pilot case-control studies using different control groups, 2008–2009 season, Spain. Vaccine 2010;28:2903-7.
45. Dean AS, Moffatt CR, Rosewell A, et al. Incompletely matched influenza vaccine still provides protection in frail elderly. Vaccine 2010;28:864-7.
46. Centers for Disease Control and Prevention (CDC), Robinson S, Smith P, et al. Influenza outbreaks at two correctional facilities – Maine, March 2011. MMWR. Morbidity and Mortality Weekly Report 2012;61:229-32.
47. World Health Organization (WHO), Western Pacific Region. WHO interim recommendations for the protection of persons involved in the mass slaughter of animals potentially infected with highly pathogenic avian influenza viruses. Manila, Philippines: WHO Western Pacific Region; 2004. 
48. Ma W, Kahn RE, Richt JA. The pig as a mixing vessel for influenza viruses: human and veterinary implications. Journal of Molecular and Genetic Medicine 2009;3:158-66.
49. Marti F, Steffen R, Mutsch M. Influenza vaccine: a travelers' vaccine? Expert Review of Vaccines 2008;7:679-87.
50. Walter EB, Neuzil KM, Zhu Y, et al. Influenza vaccine immunogenicity in 6- to 23-month-old children: are identical antigens necessary for priming? Pediatrics 2006;118:e570-8.
51. Englund JA, Walter EB, Gbadebo A, et al. Immunization with trivalent inactivated influenza vaccine in partially immunized toddlers. Pediatrics 2006;118:e579-85.
52. Skowronski DM, Hottes TS, Chong M, et al. Randomized controlled trial of dose response to influenza vaccine in children aged 6 to 23 months. Pediatrics 2011;128:e276-89.
53. Domachowske JB, Pankow-Culot H, Bautista M, et al. A randomized trial of candidate inactivated quadrivalent influenza vaccine versus trivalent influenza vaccines in children aged 3–17 years. Journal of Infectious Diseases 2013;207:1878-87.
54. Tse A, Tseng HF, Greene SK, Vellozzi C, Lee GM. Signal identification and evaluation for risk of febrile seizures in children following trivalent inactivated influenza vaccine in the Vaccine Safety Datalink Project, 2010–2011. Vaccine 2012;30:2024-31.
55. Nichol KL, D'Heilly SJ, Greenberg ME, Ehlinger E. Burden of influenza-like illness and effectiveness of influenza vaccination among working adults aged 50–64 years. Clinical Infectious Diseases 2009;48:292-8.
56. Greenhawt MJ, Li JT, Bernstein DI, et al. Administering influenza vaccine to egg allergic recipients: a focused practice parameter update. Annals of Allergy, Asthma and Immunology 2011;106:11-6.
57. Mullins RJ, Gold MS. Influenza vaccination of the egg-allergic individual [letter]. Medical Journal of Australia 2011;195:52-3.
58. Erlewyn-Lajeunesse M, Brathwaite N, Lucas JS, Warner JO. Recommendations for the administration of influenza vaccine in children allergic to egg. BMJ 2009;339:912-5.
59. Kelso JM. Administration of influenza vaccines to patients with egg allergy: update for the 2010–2011 season [letter]. Journal of Allergy and Clinical Immunology 2010;126:1302-4.
60. Des Roches A, Paradis L, Gagnon R, et al. Egg-allergic patients can be safely vaccinated against influenza [letter]. Journal of Allergy and Clinical Immunology 2012;130:1213-6.e1.
61. Australasian Society of Clinical Immunology and Allergy (ASCIA). Guidelines: vaccination of the egg-allergic individual. Sydney: ASCIA; 2017. 
62. Gagnon R, Primeau MN, Des Roches A, et al. Safe vaccination of patients with egg allergy with an adjuvanted pandemic H1N1 vaccine. Journal of Allergy and Clinical Immunology 2010;126:317-23.
63. Burwen DR, Ball R, Bryan WW, et al. Evaluation of Guillain-Barré Syndrome among recipients of influenza vaccine in 2000 and 2001. American Journal of Preventive Medicine 2010;39:296-304.
64. Kawai AT, Martin D, Kulldorff M, et al. Febrile seizures after 2010–2011 trivalent inactivated influenza vaccine. Pediatrics 2015;136:e848-55.
65. Mahajan D, Roomiani I, Gold MS, et al. Annual report: surveillance of adverse events following immunisation in Australia, 2009. Communicable Diseases Intelligence 2010;34:259-76.
66. Mahajan D, Menzies R, Cook J, Macartney K, McIntyre P. Supplementary report: surveillance of adverse events following immunisation among children aged less than 7 years in Australia, 1 January to 30 June 2010. Communicable Diseases Intelligence 2011;35:21-8.
67. Wood NJ, Blyth CC, Willis GA, et al. The safety of seasonal influenza vaccines in Australian children in 2013. Medical Journal of Australia 2014;201:596-600.
68. Kieninger D, Sheldon E, Lin WY, et al. Immunogenicity, reactogenicity and safety of an inactivated quadrivalent influenza vaccine candidate versus inactivated trivalent influenza vaccine: a phase III, randomized trial in adults aged ≥18 years. BMC Infectious Diseases 2013;13:343.
69. Pépin S, Donazzolo Y, Jambrecina A, Salamand C, Saville M. Safety and immunogenicity of a quadrivalent inactivated influenza vaccine in adults. Vaccine 2013;31:5572-8.
70. Greenberg DP, Robertson CA, Landolfi VA, et al. Safety and immunogenicity of an inactivated quadrivalent influenza vaccine in children 6 months through 8 years of age. Pediatric Infectious Disease Journal 2014;33:630-6.
71. Kelly H, Carcione D, Dowse G, Effler P. Quantifying benefits and risks of vaccinating Australian children aged six months to four years with trivalent inactivated seasonal influenza vaccine in 2010. Eurosurveillance 2010;15(37):pii=19661.
72. Li-Kim-Moy J, Yin JK, Rashid H, et al. Systematic review of fever, febrile convulsions and serious adverse events following administration of inactivated trivalent influenza vaccines in children. Eurosurveillance 2015;20(24):pii=21159.
73. Pillsbury A, Cashman P, Leeb A, et al. Real-time safety surveillance of seasonal influenza vaccines in children, Australia, 2015. Eurosurveillance 2015;20(43):pii=30050.
74. Falsey AR, Treanor JJ, Tornieporth N, Capellan J, Gorse GJ. Randomized, double-blind controlled phase 3 trial comparing the immunogenicity of high-dose and standard-dose influenza vaccine in adults 65 years of age and older. Journal of Infectious Diseases 2009;200:172-80.
75. Kaka AS, Filice GA, Myllenbeck S, Nichol KL. Comparison of side effects of the 2015–2016 high-dose, inactivated, trivalent influenza vaccine and standard dose, inactivated, trivalent influenza vaccine in adults ≥65 years. Open Forum Infectious Diseases 2017;4:ofx001.
76. DiazGranados CA, Dunning AJ, Kimmel M, et al. Efficacy of high-dose versus standard-dose influenza vaccine in older adults. New England Journal of Medicine 2014;371:635-45.
77. Moro PL, Arana J, Cano M, et al. Postlicensure safety surveillance for high-dose trivalent inactivated influenza vaccine in the Vaccine Adverse Event Reporting System, 1 July 2010–31 December 2010. Clinical Infectious Diseases 2012;54:1608-14.
78. Novartis Vaccines and Diagnostics, Inc. FDA advisory committee briefing document: Fluad – seasonal adjuvanted trivalent influenza vaccine (aTIV). Vaccines and Related Biological Products Advisory Committee, meeting date: September 15, 2015 (accessed Apr 2018). 
79. Villa M, Black S, Groth N, et al. Safety of MF59-adjuvanted influenza vaccination in the elderly: results of a comparative study of MF59-adjuvanted vaccine versus nonadjuvanted influenza vaccine in northern Italy. American Journal of Epidemiology 2013;178:1139-45.
80. Vesikari T, Knuf M, Wutzler P, et al. Oil-in-water emulsion adjuvant with influenza vaccine in young children. New England Journal of Medicine 2011;365:1406-16.
81. Heikkinen T, Young J, van Beek E, et al. Safety of MF59-adjuvanted A/H1N1 influenza vaccine in pregnancy: a comparative cohort study. American Journal of Obstetrics and Gynecology 2012;207:177.e1-8.
82. DiazGranados CA, Saway W, Gouaux J, et al. Safety and immunogenicity of high-dose trivalent inactivated influenza vaccine in adults 50–64 years of age. Vaccine 2015;33:7188-93.
83. McKittrick N, Frank I, Jacobson JM, et al. Improved immunogenicity with high-dose seasonal influenza vaccine in HIV-infected persons: a single-center, parallel, randomized trial. Annals of Internal Medicine 2013;158:19-26.
84. GiaQuinta S, Michaels MG, McCullers JA, et al. Randomized, double-blind comparison of standard-dose vs. high-dose trivalent inactivated influenza vaccine in pediatric solid organ transplant patients. Pediatric Transplantation 2015;19:219-28.
85. Armstrong PK, Dowse GK, Effler PV, et al. Epidemiological study of severe febrile reactions in young children in Western Australia caused by a 2010 trivalent inactivated influenza vaccine. BMJ Open 2011;1:e000016.
86. Moro PL, Broder K, Zheteyeva Y, et al. Adverse events in pregnant women following administration of trivalent inactivated influenza vaccine and live attenuated influenza vaccine in the Vaccine Adverse Event Reporting System, 1990–2009. American Journal of Obstetrics and Gynecology 2011;204:146.e1-7.
87. Munoz FM, Greisinger AJ, Wehmanen OA, et al. Safety of influenza vaccination during pregnancy. American Journal of Obstetrics and Gynecology 2005;192:1098-106.
88. Pool V, Iskander J. Safety of influenza vaccination during pregnancy [letter]. American Journal of Obstetrics and Gynecology 2006;194:1200.
89. Tamma PD, Ault KA, del Rio C, et al. Safety of influenza vaccination during pregnancy. American Journal of Obstetrics and Gynecology 2009;201:547-52.
90. Nelson KE. Invited commentary: influenza vaccine and Guillain-Barré syndrome – is there a risk? American Journal of Epidemiology 2012;175:1129-32.
91. Nohynek H, Jokinen J, Partinen M, et al. AS03 adjuvanted AH1N1 vaccine associated with an abrupt increase in the incidence of childhood narcolepsy in Finland. PLoS One 2012;7(3):e33536.
92. Dauvilliers Y, Montplaisir J, Cochen V, et al. Post-H1N1 narcolepsy-cataplexy [letter]. Sleep 2010;33:1428-30.
93. World Health Organization (WHO). Global Vaccine Safety: statement on narcolepsy and vaccination. 2011 (accessed Apr 2018). 
94. Kim WJ, Lee SD, Lee E, et al. Incidence of narcolepsy before and after MF59-adjuvanted influenza A(H1N1)pdm09 vaccination in South Korean soldiers. Vaccine 2015;33:4868-72.
95. Tsai TF, Crucitti A, Nacci P, et al. Explorations of clinical trials and pharmacovigilance databases of MF59®-adjuvanted influenza vaccines for associated cases of narcolepsy. Scandinavian Journal of Infectious Diseases 2011;43:702-6.
96. Bresee JS, Fry AM, Sambhara S, Cox NJ. Inactivated influenza vaccines. In: Plotkin SA, Orenstein WA, Offit PA, Edwards KM, eds. Plotkin's vaccines. 7th ed. Philadelphia, PA: Elsevier; 2018.
97. Barr IG, Jelley LL. The coming era of quadrivalent human influenza vaccines: who will benefit? Drugs 2012;72:2177-85.
98. Moa AM, Muscatello DJ, Turner RM, MacIntyre CR. Epidemiology of influenza B in Australia: 2001–2014 influenza seasons. Influenza and Other Respiratory Viruses 2017;11:102-9.
99. Webster RG, Peiris M, Chen H, Guan Y. H5N1 outbreaks and enzootic influenza. Emerging Infectious Diseases 2006;12:3-8.
100. Peiris M, Yuen KY, Leung CW, et al. Human infection with influenza H9N2. The Lancet 1999;354:916-7.
101. Lester-Smith D, Zurynski YA, Booy R, et al. The burden of childhood influenza in a tertiary paediatric setting. Communicable Diseases Intelligence 2009;33:209-15.
102. Iskander M, Kesson A, Dwyer D, et al. The burden of influenza in children under 5 years admitted to The Children's Hospital at Westmead in the winter of 2006. Journal of Paediatrics and Child Health 2009;45:698-703.
103. Neuzil KM, Zhu Y, Griffin MR, et al. Burden of interpandemic influenza in children younger than 5 years: a 25-year prospective study. Journal of Infectious Diseases 2002;185:147-52.
104. Hurwitz ES, Haber M, Chang A, et al. Effectiveness of influenza vaccination of day care children in reducing influenza-related morbidity among household contacts. JAMA 2000;284:1677-82.
105. Kwok KO, Riley S, Perera RA, et al. Relative incidence and individual-level severity of seasonal influenza A H3N2 compared with 2009 pandemic H1N1. BMC Infectious Diseases 2017;17:337.
106. Lee BE, Mukhi SN, Drews SJ. Association between patient age and influenza A subtype during influenza outbreaks. Infection Control and Hospital Epidemiology 2010;31:535-7.
107. Centers for Disease Control and Prevention (CDC), Thompson MG, Shay DK, et al. Estimates of deaths associated with seasonal influenza – United States, 1976–2007. MMWR. Morbidity and Mortality Weekly Report 2010;59:1057-62.
108. Kaczmarek MC, Ware RS, Lambert SB. The contribution of PCR testing to influenza and pertussis notifications in Australia. Epidemiology and Infection 2016;144:306-14.
109. Nielsen J, Mazick A, Glismann S, Mølbak K. Excess mortality related to seasonal influenza and extreme temperatures in Denmark, 1994–2010. BMC Infectious Diseases 2011;11:350.
110. Newall AT, Scuffham PA. Influenza-related disease: the cost to the Australian healthcare system. Vaccine 2008;26:6818-23.
111. Newall AT, Wood JG, MacIntyre CR. Influenza-related hospitalisation and death in Australians aged 50 years and older. Vaccine 2008;26:2135-41.
112. Muscatello DJ, Newall AT, Dwyer DE, MacIntyre CR. Mortality attributable to seasonal and pandemic influenza, Australia, 2003 to 2009, using a novel time series smoothing approach. PLoS One 2014;8(6):e64734.
113. Chiu C, Dey A, Wang H, et al. Vaccine preventable diseases in Australia, 2005 to 2007. Communicable Diseases Intelligence 2010;34 Suppl:ix-S167.
114. Thompson WW, Shay DK, Weintraub E, et al. Influenza-associated hospitalizations in the United States. JAMA 2004;292:1333-40.
115. Poehling KA, Edwards KM, Weinberg GA, et al. The underrecognized burden of influenza in young children. New England Journal of Medicine 2006;355:31-40.
116. World Health Organization (WHO). Global Alert and Response (GAR). Pandemic (H1N1) 2009 – update 112. 2010 (accessed Apr 2018). 
117. Australian Government Department of Health and Ageing. Australian influenza surveillance report. No. 44, 2010, reporting period: 30 October – 5 November 2010 (accessed Apr 2018). 
118. Flint SM, Davis JS, Su JY, et al. Disproportionate impact of pandemic (H1N1) 2009 influenza on Indigenous people in the Top End of Australia's Northern Territory. Medical Journal of Australia 2010;192:617-22.
119. ANZIC Influenza Investigators, Webb SA, Pettila V, et al. Critical care services and 2009 H1N1 influenza in Australia and New Zealand. New England Journal of Medicine 2009;361:1925-34.
120. Australian Government Department of Health. Information brief: 2017 influenza season in Australia – a summary from the National Influenza Surveillance Committee. Canberra: Australian Government Department of Health; 2017. 
121. World Health Organization (WHO). WHO recommendations on the composition of influenza virus vaccines (accessed May 2018). 
122. Therapeutic Goods Administration. Australian Influenza Vaccine Committee (AIVC). 2016 (accessed Apr 2018). 
123. Kelly H, Carville K, Grant K, et al. Estimation of influenza vaccine effectiveness from routine surveillance data. PLoS One 2009;4(3):e5079.
124. Kelly H, Jacoby P, Dixon GA, et al. Vaccine effectiveness against laboratory-confirmed influenza in healthy young children: a case-control study. Pediatric Infectious Disease Journal 2011;30:107-11.
125. Jefferson T, Rivetti A, Di Pietrantonj C, Demicheli V, Ferroni E. Vaccines for preventing influenza in healthy children. Cochrane Database of Systematic Reviews 2012;(8):CD004879. doi:10.1002/14651858.CD004879.pub4.
126. Shuler CM, Iwamoto M, Bridges CB, et al. Vaccine effectiveness against medically attended, laboratory-confirmed influenza among children aged 6 to 59 months, 2003–2004. Pediatrics 2007;119:e587-95.
127. Joshi AY, Iyer VN, St Sauver JL, Jacobson RM, Boyce TG. Effectiveness of inactivated influenza vaccine in children less than 5 years of age over multiple influenza seasons: a case-control study. Vaccine 2009;27:4457-61.
128. Heinonen S, Silvennoinen H, Lehtinen P, et al. Effectiveness of inactivated influenza vaccine in children aged 9 months to 3 years: an observational cohort study. The Lancet Infectious Diseases 2011;11:23-9.
129. Jick H, Hagberg KW. Effectiveness of influenza vaccination in the United Kingdom, 1996–2007. Pharmacotherapy 2010;30:1199-206.
130. Monto AS, Ohmit SE, Petrie JG, et al. Comparative efficacy of inactivated and live attenuated influenza vaccines. New England Journal of Medicine 2009;361:1260-7.
131. Osterholm MT, Kelley NS, Sommer A, Belongia EA. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. The Lancet Infectious Diseases 2012;12:36-44.
132. Jackson ML, Chung JR, Jackson LA, et al. Influenza vaccine effectiveness in the United States during the 2015–2016 season. New England Journal of Medicine 2017;377:534-43.
133. Andrews N, McMenamin J, Durnall H, et al. Effectiveness of trivalent seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom: 2012/13 end of season results. Eurosurveillance 2014;19(27):pii=20851.
134. Castilla J, Martínez-Baz I, Martínez-Artola V, et al. Decline in influenza vaccine effectiveness with time after vaccination, Navarre, Spain, season 2011/12. Eurosurveillance 2013;18(5):pii=20388.
135. Beyer WE, Palache AM, Boulfich M, Osterhaus AD. Rationale for two influenza B lineages in seasonal vaccines: a meta-regression study on immunogenicity and controlled field trials. Vaccine 2017;35:4167-76.
136. Blyth CC, Macartney KK, Hewagama S, et al. Influenza epidemiology, vaccine coverage and vaccine effectiveness in children admitted to sentinel Australian hospitals in 2014: the Influenza Complications Alert Network (FluCAN). Eurosurveillance 2016;21(30):pii=30301.
137. Blyth CC, Jacoby P, Effler PV, et al. Effectiveness of trivalent flu vaccine in healthy young children. Pediatrics 2014;133:e1218-25.
138. Heikkinen T, Heinonen S. Effectiveness and safety of influenza vaccination in children: European perspective. Vaccine 2011;29:7529-34.
139. Pebody R, Andrews N, McMenamin J, et al. Vaccine effectiveness of 2011/12 trivalent seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom: evidence of waning intra-seasonal protection. Eurosurveillance 2013;18(5):pii=20389.
140. Treanor JJ, Talbot HK, Ohmit SE, et al. Effectiveness of seasonal influenza vaccines in the United States during a season with circulation of all three vaccine strains. Clinical Infectious Diseases 2012;55:951-9.
141. Fu C, He Q, Li Z, et al. Seasonal influenza vaccine effectiveness among children, 2010–2012. Influenza and Other Respiratory Viruses 2013;7:1168-74.
142. Shay DK, Chillarige Y, Kelman J, et al. Comparative effectiveness of high-dose versus standard-dose influenza vaccines among US Medicare beneficiaries in preventing postinfluenza deaths during 2012–2013 and 2013–2014. Journal of Infectious Diseases 2017;215:510-7.
143. Mannino S, Villa M, Apolone G, et al. Effectiveness of adjuvanted influenza vaccination in elderly subjects in northern Italy. American Journal of Epidemiology 2012;176:527-33.
144. Madhi SA, Cutland CL, Kuwanda L, et al. Influenza vaccination of pregnant women and protection of their infants. New England Journal of Medicine 2014;371:918-31.
145. Regan AK, de Klerk N, Moore HC, et al. Effectiveness of seasonal trivalent influenza vaccination against hospital-attended acute respiratory infections in pregnant women: a retrospective cohort study. Vaccine 2016;34:3649-56.
146. Nunes MC, Madhi SA. Influenza vaccination during pregnancy for prevention of influenza confirmed illness in the infants: a systematic review and meta-analysis. Human Vaccines and Immunotherapeutics 2017: [Epub ahead of print] doi:10.1080/21645515.2017.1345385.
147. Gherasim A, Pozo F, de Mateo S, et al. Waning protection of influenza vaccine against mild laboratory confirmed influenza A(H3N2) and B in Spain, season 2014–15. Vaccine 2016;34:2371-7.
148. Kissling E, Nunes B, Robertson C, et al. I-MOVE multicentre case-control study 2010/11 to 2014/15: is there within-season waning of influenza type/subtype vaccine effectiveness with increasing time since vaccination? Eurosurveillance 2016;21(16):pii=30201.
149. Kissling E, Valenciano M, Larrauri A, et al. Low and decreasing vaccine effectiveness against influenza A(H3) in 2011/12 among vaccination target groups in Europe: results from the I-MOVE multicentre case-control study. Eurosurveillance 2013;18(5):pii=20390.
150. Sullivan SG, Komadina N, Grant K, et al. Influenza vaccine effectiveness during the 2012 influenza season in Victoria, Australia: influences of waning immunity and vaccine match. Journal of Medical Virology 2014;86:1017-25.
151. Cheng AC, Macartney KK, Waterer GW, et al. Repeated vaccination does not appear to impact upon influenza vaccine effectiveness against hospitalization with confirmed influenza. Clinical Infectious Diseases 2017;64:1564-72.
152. Voordouw AC, Sturkenboom MC, Dieleman JP, et al. Annual revaccination against influenza and mortality risk in community-dwelling elderly persons. JAMA 2004;292:2089-95.
153. McLean HQ, Thompson MG, Sundaram ME, et al. Impact of repeated vaccination on vaccine effectiveness against influenza A(H3N2) and B during 8 seasons. Clinical Infectious Diseases 2014;59:1375-85.
154. Ohmit SE, Thompson MG, Petrie JG, et al. Influenza vaccine effectiveness in the 2011–2012 season: protection against each circulating virus and the effect of prior vaccination on estimates. Clinical Infectious Diseases 2014;58:319-27.
155. National vaccine storage guidelines: Strive for 5. 2nd ed. Canberra: Australian Government Department of Health and Ageing; 2013. 
156. Communicable Diseases Network Australia (CDNA). Influenza infection: CDNA national guidelines for public health units. Canberra: Australian Government Department of Health; 2011.