Influenza (flu)
Information about influenza (flu) disease, vaccines and recommendations for vaccination from the Australian Immunisation Handbook
Vaccination for certain groups of people is funded under the National Immunisation Program and by states and territories.
What's changed
- The indicated ages for FluQuadri and Influvac Tetra, have been extended. FluQuadri can now be used in children ≥6 months of age. Influvac Tetra can now be used in children aged ≥3 years of age.
- Vaxigrip Tetra is now registered for use in Australia and is indicated in adults and children ≥6 months of age.
- Fluad Quad (aQIV) is now registered for use in Australia and is indicated in adults ≥65 years of age.
- Fluad TIV and FluQuadri Junior have been discontinued.
- Fluzone High-Dose is not available in 2020.
Overview
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
- healthcare workers, carers and household contacts of people in high-risk groups
- residents, staff, volunteers and visitors to 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 adjuvanted quadrivalent influenza vaccine (QIV), but may receive a standard QIV if the adjuvanted QIV is 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.
Recommendations
All infants, children and adults
All people aged ≥6 months are recommended to receive influenza vaccine every year
All people ≥6 months of age are recommended to receive annual influenza vaccine.1,2
A single annual dose of influenza vaccine is recommended for most people. Usually, receiving 2 separate doses in the same season is not recommended, but not contraindicated.
The exception is that 2 doses at least 4 weeks apart are recommended for:
- 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
Infants and children
Children aged <5 years are strongly recommended to receive influenza vaccine every year
Infants and children aged 6 months to <5 years are strongly recommended to receive annual influenza vaccine.
Children aged 6 months to <5 years who are receiving influenza vaccine for the first time are recommended to receive 2 doses of influenza vaccine. They should receive the 2 doses 4 weeks apart.
These children are recommended to receive 1 dose of influenza vaccine every year after that.
Infants and children aged <5 years have a higher risk of hospitalisation and increased morbidity after influenza.3,4 This is true for all children, not just those with pre-existing medical conditions.5-7
The Therapeutic Goods Administration registers specific brands of influenza vaccine for use in children from 6 months of age. These may change each year. See Vaccine information and Vaccines, dosage and administration.
Adults
Adults aged ≥65 years are strongly recommended to receive influenza vaccine every year
Adults aged ≥65 years are strongly recommended to receive an annual dose of influenza vaccine.
The adjuvanted influenza vaccine (Fluad Quad) is recommended in preference to standard QIVs for adults aged ≥65 years. See also Vaccine information.
Influenza-associated mortality rates are highest among adults aged ≥65 years.4 Vaccinating elderly people reduces hospitalisations from influenza and pneumonia, and all-cause mortality.8
Aboriginal and Torres Strait Islander people
Aboriginal and Torres Strait Islander people are strongly recommended to receive influenza vaccine every year
Aboriginal and Torres Strait Islander people are strongly recommended to receive annual influenza vaccine.
The disease burden from influenza is significantly higher among Aboriginal and Torres Strait Islander people than among non-Indigenous Australians in all age groups. See Epidemiology and Vaccination for Aboriginal and Torres Strait Islander people.4
People with medical conditions that increase their risk of influenza
People aged ≥6 months with medical conditions associated with an increased risk of influenza disease and complications are strongly recommended to receive influenza vaccine every year
People aged ≥6 months with medical conditions specified in this List. Medical conditions associated with an increased risk of influenza disease and severe outcomes are strongly recommended to receive annual influenza vaccine.
People with these specific medical conditions have a higher risk of influenza or severe outcomes from influenza .9-29
People who have received a transplant
People who have had a haematopoietic stem cell transplant or solid organ transplant and are receiving influenza vaccine for the first time after transplant are recommended to receive:
- 2 doses at least 4 weeks apart the 1st time they receive influenza vaccine after the transplant
- 1 dose each year after that
Vaccine doses for people with the risk conditions in this list are funded under the NIP unless otherwise noted.
Conditions |
---|
Immunocompromising conditions including:
|
Functional or anatomical asplenia, including:
|
Cardiac disease, including:
|
Chronic respiratory conditions, including:
|
Chronic neurological conditions, including:
|
Chronic metabolic disorders, including:
|
Chronic renal failure |
Long-term aspirin therapy in children aged 6 months to 10 years |
Chronic liver diseasea |
Down syndromea |
Obesity (body mass index ≥30 kg per m2) a |
Children born less than 37 weeks gestationa |
Harmful use of alcohola |
a: Not funded under the NIP
Women who are pregnant or breastfeeding
Pregnant women are strongly recommended to receive influenza vaccine in each pregnancy
Pregnant women are strongly recommended to receive influenza vaccine in each pregnancy.
Women who acquire influenza during pregnancy have an increased risk of morbidity and mortality.23 Women who acquire influenza are also at higher risk of preterm birth.30-39
Vaccinating pregnant women also protects their infants from influenza in the first 6 months of life. This is due to transplacental transfer of influenza-specific antibodies.31,40,41
Timing of influenza vaccination during pregnancy
Pregnant women can receive influenza vaccine during any stage of pregnancy.
Influenza vaccine can safely be given at the same time as dTpa (reduced antigen content diphtheria-tetanus-acellular pertussis) vaccine.
Women who received the previous year’s seasonal influenza vaccine early in their pregnancy can receive the current seasonal influenza vaccine (when it becomes available) later in the same pregnancy. Women who received vaccine before becoming pregnant should be revaccinated during pregnancy to protect the unborn infant.
Influenza vaccine can safely be given to breastfeeding women.
See Table. Vaccines that are routinely recommended in pregnancy: inactivated vaccines in Vaccination for women who are planning pregnancy, pregnant or breastfeeding for more details.
Occupational groups
Healthcare workers, carers and household contacts of people in high-risk groups are strongly recommended to receive influenza vaccine every year
Healthcare workers, carers and household contacts of people in high-risk groups are strongly recommended to receive annual influenza vaccine.
Healthcare workers, carers and household contacts who should be vaccinated include:
- all healthcare providers, particularly those caring for people who are immunocompromised
- household contacts (including children ≥6 months of age) of people in high-risk groups, including people who provide home care to people at high risk of influenza
- people working in early childhood education and care
- staff or volunteers caring for homeless people
This is because these people can transmit influenza to people who have a higher risk of complications from influenza infection.
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.42 Employers should consider the benefits of offering influenza vaccine in their workplace, particularly for occupations at higher risk of influenza.
See Recommended vaccines for people at increased risk of certain occupationally acquired vaccine-preventable diseases in Vaccination for people at occupational risk.
Residents, staff, volunteers and visitors to aged care and long-term residential facilities are strongly recommended to receive influenza vaccine every year
All residents, staff, volunteers and visitors to aged care and long-term residential facilities are strongly recommended to receive annual influenza vaccine.
These people include inmates of correctional facilities and people in immigration detention centres.
This is due to high rates of influenza transmission and complications during outbreaks in these facilities.22,43-45
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.42 Employers should consider the benefits of offering influenza vaccine in their workplace, particularly for occupations at higher risk of influenza.
Commercial poultry and pork industry workers are strongly recommended to receive influenza vaccine during an outbreak of avian or swine influenza
During an outbreak of avian influenza or swine influenza, influenza vaccination is strongly recommended for:46
- people who work in the poultry or pork industries
- people in regular close contact with poultry or pigs
Routine seasonal influenza vaccination does not protect against avian or swine influenza. However, it is possible that, if a person is co-infected with avian or swine and human strains of influenza virus, the 2 strains could reassort and form a virulent strain. This strain could then spread from human to human and start a pandemic. This was the case with the swine influenza pandemic in 2009.47
Influenza vaccination can also prevent humans from transmitting influenza to animals.
Essential services providers are strongly recommended to receive influenza vaccine every year
People who provide essential community services are strongly recommended to receive annual influenza vaccine.
Influenza infections can place considerable pressure on both public and private healthcare services. Vaccinating people who provide essential services can minimise disruption of essential activities during influenza outbreaks.
See Recommended vaccines for people at increased risk of certain occupationally acquired vaccine-preventable diseases in Vaccination for people at occupational risk.
Travellers
People who are travelling during the influenza season are strongly recommended to receive influenza vaccine
People who are travelling are strongly recommended to receive influenza vaccine, especially if influenza is circulating in the destination region or in settings with increased risk of influenza circulation during the trip, such as:48
- travellers in large tourist groups (especially those including older people)
- travellers on cruises
- travellers participating in mass gatherings (for example travellers on pilgrimage to Mecca)
Australians who have received a current Southern Hemisphere influenza vaccine and are travelling later in the year to the Northern Hemisphere during their influenza season (usually October to May) may receive a second dose of influenza vaccine within the same year. Although the current formulation for use in the Northern Hemisphere may be preferred, it is generally not available in Australia. Receiving a dose of the Southern Hemisphere formulation for this purpose is acceptable.
Factors that should be considered when deciding whether a traveller would receive a second dose of influenza vaccine within the same year in Australia before departure to the Northern Hemisphere include:
- individual assessment of potential risk of influenza and severe outcomes, according to the itinerary and personal risk factors
- similarity between the current Southern and Northern Hemisphere formulations of influenza vaccine
- availability of a reliable influenza vaccine and feasibility of receiving it at the traveller’s destination
See also Vaccination for international travellers.
Similarly, returning residents who have recently received a Northern Hemisphere influenza vaccine may also receive the current Southern Hemisphere influenza vaccine.
Other groups
Homeless people are strongly recommended to receive influenza vaccine every year
Homeless people are strongly recommended to receive annual influenza vaccine.
The living conditions of homeless people and their prevalence of underlying medical conditions mean that they are predisposed to complications from, and transmission of, influenza.
Vaccines, dosage and administration
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.
All people aged ≥6 months
Fluarix Tetra
Registered for use in people aged ≥6 months.
Quadrivalent inactivated influenza vaccine
Each 0.5 mL monodose pre-filled syringe contains:
- 15 µg haemagglutinin of each of the 4 recommended influenza virus strains
- ≤0.05 µg ovalbumin
- ≤5 µg formaldehyde
- polysorbate 80
- octoxinol 10
May contain traces of:
- gentamicin
- hydrocortisone
- sodium deoxycholate
FluQuadri
Registered for use in people aged ≥6 months.
Quadrivalent inactivated influenza vaccine
Each 0.5 mL monodose pre-filled syringe contains:
- 15 µg haemagglutinin of each of the 4 recommended influenza virus strains
- ≤100 µg formaldehyde
- ≤250 µg octoxinol 9
- ≤1 µg ovalbumin
Vaxigrip Tetra
Registered for use in people aged ≥6 months.
Quadrivalent inactivated influenza vaccine
Each 0.5 mL monodose pre-filled syringe contains:
- 15 µg haemagglutinin of each of the 4 recommended influenza virus strains
Also contains traces of:
- ovalbumin (≤ 0.05 µg)
- neomycin (≤ 10.1 pg)
- formaldehyde (≤ 30 µg)
- octoxinol-9 (≤ 222.5 µg)
All people aged ≥3 years only
Influvac Tetra
Registered for use in people aged ≥3 years.
Quadrivalent inactivated influenza vaccine
Each 0.5 mL monodose pre-filled syringe contains:
- 15 µg haemagglutinin of each of the 4 recommended influenza virus strains
- ≤100 ng ovalbumin
- ≤0.01 mg formaldehyde
- 0.02 mg cetrimonium bromide
- 1 ng gentamicin sulfate
May contain traces of:
- tylosine tartrate
- hydrocortisone
- polysorbate 80
All people aged ≥5 years only
Afluria Quad
Registered for use in people aged ≥5 years.
Quadrivalent inactivated influenza vaccine
Each 0.5 mL monodose pre-filled syringe contains:
- 15 µg haemagglutinin of each of the 4 recommended influenza virus strains
- <1 µg ovalbumin
May contain traces of:
- sodium taurodeoxycholate
- neomycin
- polymyxin B
- propiolactone
Adults aged ≥65 years only
Fluad Quad
Registered for use in people aged ≥65 years.
Adjuvanted quadrivalent inactivated influenza vaccine
Each 0.5 mL monodose pre-filled syringe contains:
- 15 µg haemagglutinin of each of the 4 recommended influenza virus strains.
These are adjuvanted with MF59C.1. The adjuvant includes:
- 9.75 mg squalene
- 1.175 mg polysorbate 80
- 1.175 mg sorbitan trioleate
- 0.66 mg sodium citrate dehydrate
- 0.04 mg citric acid monohydrate
May contain traces of:
- Kanamycin
- Neomycin
- kanamycin
- neomycin
- formaldehyde
- barium sulfate
- cetrimonium bromide
- ovalbumin
- hydrocortisone
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 0.5 mL.
Shake the pre-filled syringe vigorously before injection. Influenza vaccines are preferably given by intramuscular injection. However, they may also be given subcutaneously.
Age |
Dose |
Number of doses needed in 1st year of influenza vaccination |
Number of doses needed if person received 1 or more doses of influenza vaccine in a previous season |
6 months to <9 years |
0.5 mL |
2 (given 4 weeks apart) |
1 |
≥9 years |
0.5 mL |
1 |
1 |
People of any age who have recently had a haematopoietic stem cell transplant or solid organ transplant |
0.5 mL |
2 (given 4 weeks apart) in 1st year after transplant |
2 (given 4 weeks apart) in 1st year after transplant |
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.49,50
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.
For adults aged ≥65 years who have already received an adjuvanted influenza vaccine in the current influenza season, an extra dose of quadrivalent influenza vaccine in the same season is not recommended.
Similarly, if they have received quadrivalent influenza vaccine, an extra dose of adjuvanted influenza vaccine in the same season is not recommended.
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 any time before or after, or with, any other vaccine. However, when children receive 13vPCV and inactivated influenza vaccine at the same time, there is one report of a small increased risk of fever and febrile convulsions, compared with receiving the vaccines separately. This 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.51
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.
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.
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.
Contraindications and precautions
Contraindications
The only absolute contraindications to influenza vaccines are:
- anaphylaxis after a previous dose of any influenza vaccine
- anaphylaxis after any component of an influenza vaccine
See Precautions for more details about influenza vaccination for people with a known egg allergy.
Precautions
People with egg allergy
People with egg allergy, including a history of anaphylaxis, can be safely vaccinated with influenza vaccines.
See also Vaccinating people with a known egg allergy in Vaccination for people who have had an adverse event following immunisation.
People with known anaphylaxis egg allergy
People with a history of anaphylaxis to egg should:
- receive a full age-appropriate vaccine dose; do not split the dose into multiple injections (for example, a test and then the rest of the dose)
If there is significant parental or health professional anxiety, the vaccine may be administered in primary care settings with a longer waiting period of 30 minutes.
Several published reviews, guidelines and reports suggest a very low risk of anaphylaxis associated with influenza vaccination of egg-allergic people.52-57
A 2012 review of published studies included 4172 egg-allergic patients. 513 of these patients reported a history of severe allergic reaction to egg. The review found no cases of anaphylaxis after receiving an inactivated influenza vaccine.56
The largest study in the review included 830 egg-allergic patients. 164 of these patients reported a history of severe allergic reaction to egg. Only 17 (2%) of these patients experienced any adverse event.58 All adverse events were mild, and included abdominal pain, hives and respiratory symptoms such as wheezing.
People with known non-anaphylaxis egg allergy
People with a history of egg allergy (non-anaphylaxis) can receive an age-appropriate full dose of vaccine in any immunisation setting. This includes sensitised children (that is, children who are skin-prick or RAST-test positive) who have not yet eaten egg.
People with latex allergy
Although the product information for Fluarix Tetra states that some preparations of the vaccine cannot be considered latex-free, these preparations are not supplied in Australia.
People with a history of Guillain–Barré syndrome
People with a history of Guillain–Barré syndrome (GBS) whose first episode was not after influenza vaccination have an extremely low risk of recurrence of GBS after vaccination. Influenza vaccination is recommended for these people59-61
Influenza vaccination is generally not recommended for people with a history of GBS whose first episode occurred with 6 weeks of receiving an influenza vaccine. There is limited data on the risk of recurrence of GBS in people where the first episode occurred within 6 weeks of influenza vaccination (i.e. the first episode was possibly triggered by the vaccine). In these people, discuss the potential for recurrence if vaccinated, the potential for exacerbation following influenza infection, and other protective strategies (e.g. vaccination of household members). Vaccination can be considered in special circumstances, such as when an alternative cause for GBS, such as Campylobacter jejuni infection, was found or the risk of influenza disease is considered high.
People receiving immuno-oncology therapy
Some studies that included a small number of patients reported that people receiving cancer immuno-oncology therapies (checkpoint inhibitors) may have a higher risk of immune-related adverse events following immunisation with influenza vaccine,62,63 but a more recent study on patients receiving treatment with a single checkpoint inhibitor did not.64 The clinical importance of this potential interaction is currently inconclusive.
Checkpoint inhibitors include:
- CTLA-4 inhibitors (such as ipilimumab)
- PD-1 and PD-L1 inhibitors (such as nivolumab or pembrolizumab)
Consult the person’s treating oncologist about the risks and benefits of influenza vaccination in people taking these treatments.
Children who need both influenza and 13vPCV
Children can receive 13vPCV and inactivated influenza vaccine at the same visit if they need both vaccines.
One study found a slightly higher risk of fever and febrile convulsions in children aged 6 months to <5 years (especially those aged 12–24 months) when they received inactivated trivalent influenza vaccine and 13vPCV at the same time, compared with receiving the vaccines separately.51 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.
A later study did not show an association between co-administering these 2 vaccines and febrile seizures.65
See Co-administration with other vaccines in Vaccines, dosage and administration, and Pneumococcal disease.
Adverse events
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
- pain66-68
Studies directly comparing inactivated trivalent and quadrivalent formulations in children and adults showed that the safety profiles were similar.69-72
Systemic adverse events
1–10% of people who receive standard inactivated TIVs will develop:
- fever
- malaise
- myalgia66-68,73-75
These adverse events may start a few hours after vaccination and may last for 1–2 days.66,67,73
Immediate adverse events following influenza vaccination are very rare. They can include hives, angioedema or anaphylaxis.52,57
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.52,57 See People with egg allergy in Contraindications and precautions.
Adverse events after adjuvanted influenza vaccine
Clinical trials show a higher rate of injection site reactions in adults aged ≥65 years after receiving the adjuvanted influenza vaccine, compared with standard influenza vaccines.
Around 30% of people who received Fluad TIV reported injection site reactions, compared with around 20% of people who received standard TIV. Both groups reported similar rates (about 30%) of systemic reactions.76 Overall, a similar proportion of people vaccinated with Fluad Quad (aQIV) experience injection site and systemic reactions as those vaccinated with Fluad TIV.77
Rates of severe or serious adverse events do not increase after receiving the adjuvanted vaccine. This has been shown in clinical trials and post-licensure surveillance studies.76-79
Adjuvanted influenza vaccine is only registered for use in people aged ≥65 years. This vaccine is not recommended in younger people. However, clinical trials in some younger populations and post-licensure safety data after an adjuvanted vaccine was inadvertently given to younger people suggest a similar safety profile to that seen in people aged ≥65 years.80-82
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.83
The Fluvax and Fluvax Junior vaccines are no longer available in Australia and available Seqirus vaccines have been reformulated.
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.84-87 Several systematic reviews have shown no association between influenza vaccination in pregnancy and adverse birth outcomes.88,89
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 If GBS is suspected it is preferable that an experienced clinician confirms the diagnosis so recommendations can be made regarding future influenza vaccination.
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 have never been 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
Nature of the disease
Influenza viruses are single-stranded RNA orthomyxoviruses. They are classified antigenically as types A, B, C or D. Generally, only influenza A and B cause severe disease in humans.96
Surface glycoprotein antigens
Influenza viruses have 2 surface glycoprotein antigens:
- haemagglutinin (H), which is involved in cell attachment during infection
- neuraminidase (N), which facilitates the release of newly synthesised virus from the cell
Influenza A viruses can be classified into subtypes based on differences in these surface antigens, but influenza B viruses cannot. There are 2 distinct influenza B lineages that co-circulate in varying proportions from year to year: B/Victoria and B/Yamagata.97,98
Antibodies against the surface antigens, particularly haemagglutinin, reduce infection or severe illness due to influenza.
Antigenic drift and seasonal influenza
The surface antigens of influenza A and influenza B viruses change often. The changes involve stepwise mutations of genes coding for H and N glycoproteins. This results in cumulative changes in influenza antigens, called antigenic drift. Antigenic drift is responsible for the annual outbreaks and epidemics of influenza. The composition of influenza vaccines needs to be reviewed every year because of antigenic drift.
Antigenic shift and pandemic influenza
Antigenic shift is a dramatic change in the H antigen (and other antigens) of influenza A. This occurs unpredictably and infrequently.96 Antigenic shift gives rise to pandemic influenza subtypes by 1 of 2 ways:
- an avian or other animal (such as swine) virus directly adapts so that it can infect humans
- an avian or other animal (such as swine) virus mixes with a human virus, called genetic reassortment
There have been 4 influenza pandemics in the 20th and 21st centuries:
- 1918 (H1N1)
- 1957 (H2N2)
- 1968 (H3N2)
- 2009 (H1N1)
Each of these pandemic strains replaced the previously circulating influenza A subtype and went on to circulate as seasonal influenza.
More recently, various avian influenza A virus subtypes have caused human infections. Examples are H5N1, H7N9 and H9N2. Sustained human-to-human transmission of these subtypes has not been reported.99,100
Pathogenesis
The incubation period for influenza is usually 2 days, but ranges from 1 to 4 days. Virus can be detected in the upper airway for up to 1 day before symptoms start and around 3–5 days after illness finishes in adults. Children may shed virus for up to 2 weeks. Severely immunocompromised people can shed virus for months.96
Transmission
People transmit influenza from person to person:
- through virus-containing respiratory aerosols produced during coughing or sneezing
- by direct contact with respiratory secretions96
Interspecies transmission (such as from birds to humans) can result in severe illness. In rare cases, transmission of a novel virus into the human population from animals can cause a pandemic.96
Clinical features
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
- encephalitis and/or encephalopathy
- 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: 9-29
- 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 obesity (BMI ≥30 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
Epidemiology
Minor or major epidemics of influenza A or influenza B influenza occur in most years, usually during the winter months in temperate regions. The impact of influenza is often substantially underestimated.
Influenza activity varies from year to year, and depends on the circulating virus and the population’s susceptibility.101
Changes in influenza detection methods have affected influenza detection and notification patterns.113 This includes an increase in the routine use of PCR-based laboratory testing in recent years.
During annual epidemics of influenza, morbidity and mortality are higher among pregnant women and people with chronic diseases than in other people.5,23,108
Influenza in Australia
On average each year in Australia, influenza causes approximately 100 deaths and 5100 hospitalisations.4,109 These numbers are widely believed to under-represent the true burden of influenza disease in Australia.
A study using mathematical modelling estimated that there are more than 3000 deaths and more than 13,500 hospitalisations due to influenza per year among Australians aged >50 years.110
Another mathematical modelling study estimated the annual rate of seasonal influenza A mortality to be as high as 25.8 per 100,000 population in Australians aged ≥65 years.111
In Australia, as in other developed countries, older people and children <5 years of age have the highest rates of influenza hospitalisation.4,112-114 The disease burden from influenza is also greater in Aboriginal and Torres Strait Islander people than in non-Indigenous Australians across all age groups.4
During the 2009 A(H1N1)pdm09 pandemic, the predominant clinical presentation was mild to moderate illness. However, young healthy adults, pregnant women, and Aboriginal and Torres Strait Islander people were over-represented among severe cases compared with previous seasonal outbreaks.4,115,116
In 2017, a severe influenza season with the highest levels of activity since the 2009 pandemic year was recorded. New South Wales hospitals introduced rapid influenza testing, which may have partly contributed to the increased number of laboratory-confirmed notifications of influenza. Nationally, there were about 750 deaths among notified cases of laboratory-confirmed influenza in 2017.117
Vaccine information
Each year, the World Health Organization recommends the strains to be included in influenza vaccines based on global influenza epidemiology.118 The Australian Influenza Vaccine Committee uses this recommendation to determine the influenza virus composition of vaccines for use in Australia.119
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.
Inactivated 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.
Standard influenza vaccines contain 15 µg of haemagglutinin per strain per dose with no adjuvant. In 2020 an adjuvanted QIV (Fluad Quad) is available. The adjuvanted QIV contains MF59 as the adjuvant, and the standard 15 µg of haemagglutinin per strain per dose. The vaccine is formulated to induce a greater immune response than standard influenza vaccines.
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 community44,120-127
QIVs and TIVs
Most evidence regarding 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.128 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.129
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.130,131 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.132
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.133-138
Influenza vaccines in adults aged ≥65 years
Standard-dose influenza vaccines provide less protection against influenza 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.78,139
Most evidence on the effectiveness of adjuvanted influenza vaccine compares adjuvanted TIV with standard dose TIV. There are no studies on adjuvanted QIV effectiveness, but a study comparing adjuvanted QIV with adjuvanted TIV showed that the adjuvanted QIV not inferior in terms of generating immune responses against the shared strains and is superior for the B strain not included in the adjuvanted TIV.77 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.140
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 illness141,142
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%.143 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.130,131,136,144-147 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.44,127
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.148 Also, data collected over 6 influenza seasons show that repeated annual influenza vaccination 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.149
However, a few studies, mainly in the United States, suggest that influenza vaccines are not as effective if they are repeated year after year.150,151 Reduced effectiveness following repeated annual vaccination has not been observed consistently across studies. Better understanding of these effects is needed to determine clinical significance and guide recommendations.
Despite conflicting opinion about the impact of repeated annual vaccination on vaccine effectiveness, vaccinated people are still better protected against influenza than unvaccinated people.
Transporting, storing and handling vaccines
Transport according to National vaccine storage guidelines: Strive for 5.152 Store at +2°C to +8°C. Do not freeze. Protect from light.
Discard influenza vaccines appropriately when they reach their expiry date. This is to avoid accidentally using a product with the incorrect formulation the following year.
Public health management
Laboratory-confirmed cases of influenza are notifiable in all states and territories in Australia.
The Communicable Diseases Network Australia national guidelines for influenza infection153 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.
Variations from product information
Egg allergy
The product information for Influvac Tetra lists allergy to egg as a contraindication.
The product information for Fluad Quad and Afluria Quad state that people with egg allergy (non-anaphylaxis) can receive an age-appropriate dose.
The Australian Technical Advisory Group on Immunisation recommends that all people with egg allergies can receive an age-appropriate influenza vaccine. See Precautions.
Fluad Quad
The product information for Fluad Quad states that Fluad Quad should be given intramuscularly.
The Australian Technical Advisory Group on Immunisation recommends that Fluad Quad can also be given subcutaneously.
FluQuadri
The product information for FluQuadri states that FluQuadri should be given intramuscularly.
The Australian Technical Advisory Group on Immunisation recommends that FluQuadri can also be given subcutaneously.
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Page history
Editorial changes to recommendations for preterm infants, people travelling in the influenza season, and co-administration with other vaccines.
Updates to influenza information in line with the ATAGI annual statement for seasonal influenza vaccines
Definitions
- dTpa
- diphtheria-tetanus-acellular pertussis vaccine, reduced antigen content formulation
- 13vPCV
- 13-valent pneumococcal conjugate vaccine
- GBS
- Guillain-Barré syndrome
- RNA
- ribonucleic acid
- PCR
- polymerase chain reaction
- WHO
- World Health Organization
- DT
- diphtheria-tetanus vaccine
- ASCIA
- Australasian Society of Clinical Immunology and Allergy
- WA
- Western Australia
- CDNA
- Communicable Diseases Network Australia
- ATAGI
- Australian Technical Advisory Group on Immunisation