COVID-19

What

COVID-19 is an infectious disease caused by the severe acute respiratory coronavirus 2 (SARS-CoV-2) virus. It affects people of all ages. Older adults and people with certain medical conditions have an increased risk of severe disease or death from COVID-19.

Who

COVID-19 vaccination is recommended for all people aged 18 years and older. It is also recommended for children aged 6 months to less than 17 years with medical conditions that may increase their risk of severe disease or death from COVID-19.

How

Primary course vaccination is recommended for all people aged 18 years and older, and for children aged 6 months to less than 17 years with medical conditions that may increase their risk of severe disease or death from COVID-19. 

Most people require 1 dose for their primary course. People with severe immunocompromise are recommended 2 primary doses and can consider a 3rd. 

Further doses every 6 or 12 months may be recommended based on an individual’s age and presence of risk factors for severe disease. 

Why

COVID-19 can cause severe illness particularly in older adults, including aged care residents,  and in people with medical risk conditions.  Vaccination reduces the risk of severe disease and death from COVID-19.

COVID-19 vaccines available in Australia

The Therapeutic Goods Administration website provides product information for each vaccine, including the recently registered Comirnaty JN.1 vaccines.

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

Dose and route

All currently available COVID-19 vaccines are administered intramuscularly. The dose varies by brand and age. Refer to vaccine details above for further information.

A person may be vaccinated for the primary course earlier than the recommended interval (a minimum of 3 weeks) in exceptional circumstances, such as before starting immunosuppressant therapy, before overseas travel or if someone cannot reschedule vaccination easily (such as in an outreach vaccination program).

Co-administration with other vaccines

People aged ≥5 years

COVID-19 vaccines can be co-administered with other vaccines in people aged ≥5 years.

Studies demonstrate the safety and immunogenicity of co-administration of COVID-19 and influenza vaccines.^37-39 COVID-19 vaccines can also be co-administered with other vaccines if required, including routine childhood and adolescent vaccines. 

Replicating mpox vaccines (such as ACAM2000) and mRNA COVID-19 vaccines both carry a small risk of myocarditis, but the risk from non-replicating MVA-BN mpox vaccines remains unknown. If the timing of MVA-BN is not urgent, consider spacing apart MVA-BN mpox vaccine and mRNA COVID-19 vaccines by four weeks, to allow attribution for any adverse reaction. This is particularly relevant for young males or people with specific relevant concerns.

Children aged 6 months to <5 years

For children aged 6 months to <5 years it is preferable to separate administration of COVID-19 vaccine from other vaccines by 7–14 days.

There are limited data on the safety and immunogenicity of co-administration in this age group. Theoretically, co-administration may lead to higher rates of adverse events, including fever. However, COVID-19 vaccines can be co-administered if separation of vaccines would be logistically challenging.

Interchangeability of COVID-19 vaccines

It is generally preferable to use the same brand of COVID-19 vaccine for the primary course when multiple doses are recommended (e.g. people aged ≥5 years who are severely immunocompromised).

A dose of the latest available variant vaccine is preferred to complete a primary course in people who have started with a different formulation. If possible, the primary course should be completed using the same brand. An alternative brand can be used for subsequent doses if:

• there are contraindications or precautions to the brand used for a previous dose
• the brand used for a previous dose is not available in Australia
• the person is unable to access the same brand or does not accept further doses of a particular brand

The recommended interval between doses of a mixed schedule is 8–12 weeks, regardless of which brands are used.

Doses do not need to be repeated if the interval between doses is >12 weeks.

Mixed schedules for children who turn 5 or 12 between doses

Children who are recommended multiple primary doses and who turn 5 or 12 between doses should receive the appropriate brand and dose for their age on the day of vaccination. For example, a child with severe immunocompromise who turns 5 after receiving a first dose of Comirnaty JN.1 6 months to <5 years formulation (yellow cap) or Comirnaty Omicron XBB.1.5 6 months to <5 years formulation (maroon cap) should receive the respective Comirnaty JN.1 or Omicron XBB.1.5 5 to <12 years formulation (light blue cap) for their second dose, and a child with severe immunocompromise who turns 12 after a first dose of Comirnaty JN.1 5 to <12 years formulation (light blue cap) or Comirnaty Omicron XBB.1.5 5 to <12 years formulation (light blue cap) should the receive respective Comirnaty JN.1 or Omicron XBB.1.5-based formulation registered for use in people aged ≥12 years for their second dose.

Contraindications

COVID-19 vaccines are contraindicated in people who have had:

• anaphylaxis after a previous dose of a COVID-19 vaccine from the same class
  • anaphylaxis after one mRNA COVID-19 vaccine is a contraindication to all mRNA COVID-19 vaccines
• anaphylaxis after any component of that COVID-19 vaccine

Precautions

People with certain cardiac conditions

People with a history of any of the following conditions can receive a COVID-19 vaccine, but advice should be sought from a GP, immunisation specialist or cardiologist about the best timing of vaccination and whether any additional precautions are recommended:

• recent (within the past 3 months) myocarditis or pericarditis
• acute rheumatic fever or acute rheumatic heart disease (with active myocardial inflammation)
• acute decompensated heart failure.

People who develop myocarditis and/or pericarditis after a COVID-19 vaccine should defer further doses and discuss options for further COVID-19 vaccination with their treating doctor.

Adverse events after Comirnaty Original

Children aged 6 months to <5 years

The most frequently reported adverse events in children aged 6–23 months in the clinical trial were irritability (in about 40-50%), drowsiness (in about 25%), injection site tenderness (in about 15%), and fever (in about 7%).⁴⁰ Adverse events occurred at similar frequencies after the first and second dose and were slightly less frequent after the third dose. 

In children aged 2–4 years, adverse events occurred at similar frequencies after the first, second and third doses.⁴⁰ The most frequently reported adverse events in the clinical trial were injection site pain and fatigue (in about 25–30%). Fever was reported in about 5% of recipients.

Children aged 5–11 years

The most commonly reported adverse event after Comirnaty Original in children aged 5–11 years in the clinical trial was injection site pain (in about 70–75%), followed by fatigue (in about 35%) and headache (in about 20–30%).⁴¹ Fever occurred in 3% of children after the first dose and 6.5% of children after the second dose. 

Adverse events after Comirnaty JN.1

As SARS-CoV-2 has evolved, newer COVID-19 vaccines have been developed to target newer, more immune-evasive variants. Many updated formulations differ from the original formulation only in the specific spike protein antigen used, and therefore updated formulation (e.g. JN.1/ XBB.1.5) COVID-19 vaccines were approved by regulatory agencies, such as the Therapeutic Goods Administration (TGA), after extrapolating safety data from large phase 3 clinical trials of the original and earlier formulation COVID-19 vaccines. Data on common local and systemic adverse events are not available for Comirnaty JN.1 but the adverse event profile of Comirnaty JN.1 is expected to be similar to that of earlier formulations.

Adverse events after Comirnaty Omicron XBB.1.5

Data on common local and systemic adverse events are emerging. The adverse event profile of Comirnaty Omicron XBB.1.5 is expected to be similar to earlier formulations. A recent phase 2/3 trial among individuals aged 12 years and older reported local and systemic reactions were mostly mild to moderate in severity, similar to earlier formulations.⁴²

Anaphylaxis after COVID-19 vaccines 

Anaphylaxis after COVID-19 vaccines is rare and occurs at a similar rate to other common vaccines. In a study that included Comirnaty Original and Spikevax Original, the overall rate of anaphylaxis was around 10 per million doses.⁴³ 

Myocarditis and Pericarditis

Myocarditis and/or pericarditis following vaccination with a COVID-19 vaccine are very rare but have been reported following receipt of all currently available COVID-19 vaccines. The highest incidence has been reported in adolescent males after a second dose of an mRNA vaccine (e.g. Comirnaty), although cases have been reported in male and female adults of all ages and after any dose of a COVID-19 vaccine.^44,45

It is recommended that all COVID-19 vaccine recipients be made aware of the potential signs and symptoms of myocarditis or pericarditis and be counselled to seek medical attention if they develop. See Adverse events following immunisation.

Safety of COVID-19 vaccines during pregnancy or breastfeeding

mRNA COVID-19 vaccines are safe in pregnancy.^46-48 

The adverse event profile of pregnant women is similar to that of non-pregnant women following vaccination with an original mRNA COVID-19 vaccine.^49,50 Pregnant women are slightly more likely to report injection site pain, and less likely to report generalised symptoms such as fever or tiredness.

Coronavirus disease (COVID-19) is caused by the severe acute respiratory coronavirus 2 (SARS-CoV-2), a single-stranded RNA betacoronavirus first identified in December 2019.  

SARS-CoV-2 contains 4 main structural proteins: spike (S) glycoprotein, small envelope (E) glycoprotein, membrane (M) glycoprotein and nucleocapsid (N) protein.⁵¹ Most COVID-19 vaccines target the spike protein which allows the virus to enter cells. 

Since its discovery, variant strains have progressively become dominant due to advantages in transmissibility or immune escape from immunity acquired from prior infection or vaccination. Future virus mutations are anticipated, leading to new SARS-CoV-2 variants with immune escape, and seasonal factors.^52-54

Since 2024, Omicron is the only variant circulating globally.⁵⁵ Previous variants of concern (e.g. Alpha, Beta, Gamma, Delta) and the ancestral strain have largely disappeared. Numerous sub-lineages of Omicron have caused distinct global waves of infection.⁵⁶

Pathogenesis

In most people, SARS-CoV-2 primarily infects cells lining the upper airway and causes mild to moderate disease. Individuals with severe disease develop an infection of the lower respiratory tract causing pneumonia and may have poor or mistimed immune responses that cause both local inflammatory responses and a systemic pro-inflammatory state that leads to severe immunopathology.⁵⁷

People at increased risk of severe COVID-19 disease

Risk factors for severe disease

Older age 

Older age is by far the strongest risk factor associated with morbidity and mortality from COVID-19.^7,9,58-60 A study that assessed the mortality risk from COVID-19 among people who have received a primary course and further dose found a 30-fold greater risk of death in a person aged 80 compared with a person aged 50.⁷

Medical conditions 

Medical conditions also independently increase the risk of severe disease but to a lesser extent than age.⁶¹ For a list of these conditions see Table. Severely immunocompromising conditions for which additional doses of COVID-19 vaccine are recommended and Table. Conditions for which COVID-19 vaccination can be considered.

Pregnancy

Unvaccinated pregnant women with COVID-19 have an increased risk of severe disease compared with unvaccinated non-pregnant women of reproductive age with COVID-19.^29,62 This risk appears to be substantially reduced during the Omicron period in women who have been vaccinated.^27,63

Transmission

SARS-CoV-2 is spread via respiratory droplets or aerosols generated through breathing, talking or coughing.⁶⁴ Airborne viral particles may be inhaled, contact mucous membranes in the mouth, eyes, or nose, or land on surfaces and cause infection through contact with contaminated surfaces which are transferred to the body.

Symptoms of COVID-19 disease

The most common symptoms reported following infection with the SARS-CoV-2 Omicron variant are runny nose, sore throat, sneezing and headache.⁶⁵ Some features of COVID-19 which were associated with previous variants such as fever, loss of smell and persistent cough appear to be less commonly reported with Omicron infection. 

Severe disease and hospitalisation is less common with the Omicron variant than with previous variants, and this may be partially due to accumulating immunity from a combination of vaccination and prior infection.⁶⁶

The incubation period after exposure to SARS-CoV-2 (Omicron) is most commonly 3 days, but can be up to 14 days.⁶⁷

Complications and sequelae of COVID-19 disease

Severe COVID-19 can be fatal. An estimate of infection fatality rate (IFR) early during the Omicron period in a Danish study was 6·2 (95% CI: 5·1–7·5) per 100 000 infections.⁶⁸

A range of metabolic, cardiovascular, respiratory, immunological and neurological sequelae following COVID-19 have been reported in the literature.^69-73 

Post-COVID-19 condition ('long COVID') is currently not well defined, but generally consists of persistent symptoms that develop during or after COVID-19, continue for greater than 3 months after the onset of the illness, and are not explained by an alternative cause.⁷⁴ This can consist of various physical symptoms (e.g. fatigue, dyspnoea, chest pain, and cough), cognitive symptoms (memory and concentration issues) and psychological symptoms (anxiety, depression, post-traumatic stress disorder). 

The prevalence of post-COVID-19 condition is highly variable due to differing definitions. A systematic review and meta-analysis including over 750,000 participants reported that 45% of COVID-19 survivors experience a range of unresolved symptoms at 4 months.⁷⁵ Risk factors for post-COVID-19 condition may include the presence of comorbidities, prior hospitalisation from COVID-19, female sex, older age, high body mass index and smoking.⁷⁶

Vaccinated people have a significantly lower risk of post-COVID-19 condition (OR: 0.57; 95% CI: 0.43-0.76).⁷⁶

COVID-19 disease in Australia

Serosurveys indicate that an increasingly large proportion of the Australian population had COVID-19 by December 2022, with the highest proportion among adults being in those aged 18–29 years, where approximately 82% of the population have serological evidence of infection.⁷⁷ Similarly, approximately 80% of unvaccinated children had COVID-19 by August 2022.⁷⁸

Original vaccines were directed at, or contained, the ancestral spike protein only. Omicron-based vaccines have since been developed. Currently available Comirnaty JN.1 vaccines are formulated against the Omicron JN.1 subvariant, and available monovalent Omicron XBB.1.5 vaccines are formulated against the Omicron XBB.1.5 subvariant.

Omicron-based COVID-19 vaccines

There are limited direct data on the immunogenicity or efficacy of Omicron-based vaccines (JN.1 or XBB.1.5) for primary course vaccination. Their use for the primary course is based on the superior immunogenicity and vaccine effectiveness against current and emerging Omicron sub-variants, when evaluated as further doses. 

JN.1 vaccine effectiveness

Currently, estimate of vaccine effectiveness is not yet available for JN.1 however it has been seen that the effectiveness of vaccines matched to the currently circulating Omicron variants appears to be higher than mismatched vaccines.^4,79 Consistent with this observation, a decrease in effectiveness of XBB vaccines against COVID-19 caused by JN.1 lineage viruses has been reported.^4,79

JN.1 vaccine immunogenicity

Currently, estimate of vaccine immunogenicity is not yet available for JN.1. However, a recent preprint study looking at humoral immunity of JN.1 vaccination among 42 healthcare workers in Germany reported significant increase (1 to 2-fold) of anti-S IgG at 13 days post vaccination and strengthened neutralising responses against circulating SARS-CoV-2-variants such as JN.1 and KP.2.⁸⁰

XBB.1.5 vaccine effectiveness

XBB.1.5 vaccine effectiveness studies continue to emerge. Findings from two^81,82 large cohort studies of adults mostly ≥60 years of age demonstrated that XBB.1.5 vaccines protect against hospitalisation and ICU admission from COVID-19 for at least 2–4 weeks. Vaccine effectiveness against hospitalisation was reported as 55–77%, and against ICU admission as 73%.

XBB.1.5 vaccine immunogenicity 

Immunogenicity data in mice demonstrate a rise in neutralising antibodies against the Omicron XBB.1.5 subvariant that was approximately 33 times higher after mice received a 2-dose primary series of Pfizer monovalent XBB.1.5 vaccine, compared to a primary series of Pfizer bivalent (original/BA.4/5) vaccine.⁸³ In mice that had received a 2-dose primary course of Pfizer original (ancestral strain) vaccine, a further dose with Pfizer monovalent XBB.1.5 resulted in a level of neutralising antibody against XBB.1.5 that was approximately 5 times higher compared to a further dose with Pfizer bivalent (original/BA.4/5) vaccine.⁸³

Early human immunogenicity data^42,84 demonstrate Omicron XBB.1.5 vaccine strongly increased anti-spike IgG in all vaccines 8–10 days after a dose and elicited potent neutralising responses against previous and contemporary SARS-CoV-2 lineages.

Original COVID-19 vaccines

Comirnaty Original

In children aged 5-11 years without evidence of previous SARS-CoV-2 infection, the 10 µg dose of paediatric Comirnaty was 90.7% effective (95% CI: 67.7–98.3%) at preventing laboratory-confirmed symptomatic COVID-19 in the pre-Omicron era.⁴¹

Comirnaty Original had a vaccine efficacy of 82.3% (95% CI: -8.0–98.3%) against confirmed COVID-19 due to Omicron in children aged 2-4 years, and 75.6% (95% CI: -370.1–99.6%) in children aged 6-23 months.⁴⁰

Vaccine efficacy estimates are not available for booster doses in children aged <16 years. A clinical trial showed an increase in neutralising antibodies against the ancestral and early Omicron variants of SARS-CoV-2 after a first booster dose in children aged 5-11 years who had no evidence of past infection.⁸⁵

No formulation of Comirnaty Original is currently available in Australia.

Currently available COVID-19 vaccines are presented as multi-dose vials or single use prefilled syringes. For guidance on handling of multi-dose vials, refer to Administration of vaccines.

Multi-dose mRNA COVID-19 vaccine vials are initially stored frozen at ultra-cold temperatures and once thawed can be stored in a fridge for a certain period before use. Requirements differ by vaccine brand and vial; for more information see COVID-19 vaccines in Australia - Poster.  

General advice:

• Thawed vials of frozen vaccine should not be refrozen.
• Do not shake the vaccine vials. 
• Minimise exposure to room light and avoid direct sunlight and ultraviolet light.
• Once a multi-dose vial is punctured, use prepared doses within 6 hours.

For general information on vaccine storage, see the National Vaccine Storage Guidelines Strive for 5.⁸⁶

COVID-19 is a notifiable disease in all states and territories in Australia.

The Communicable Diseases Network Australia provides national guidelines and the State and territory public health authorities can provide local advice about the public health management of COVID-19, including management of cases and their contacts.

Serological testing for immunity

It is not recommended to test for anti-spike antibodies or neutralising antibodies to demonstrate immunity against SARS-CoV-2 in vaccinated people as there is currently no established immune correlate of protection and the available assays for anti-spike antibody or neutralising antibodies vary in their interpretation.

Impact of vaccination on future COVID-19 testing

Receiving a COVID-19 vaccine will not affect the results of nucleic acid (PCR) testing or rapid antigen testing for diagnosis of SARS-CoV-2 infection. However, as vaccines induce protective antibodies against the spike protein, this may result in serological testing detecting antibody to the spike protein. Vaccination will not affect the results of anti-nucleocapsid antibody testing.

Post-exposure prophylaxis

COVID-19 vaccines are not recommended for post-exposure prophylaxis. No data are available to support such use.

The product information for Comirnaty state that the recommended interval between primary course doses is 3 weeks. ATAGI recommends an 8-week interval between primary course doses. 

The product information states that recommended interval between primary course and further doses is at least 3-6 months. ATAGI recommends a minimum interval between primary course and further doses of at least 6 months in eligible people. 

1. Zhu Y, Almeida FJ, Baillie JK, et al. International pediatric COVID-19 severity over the course of the pandemic. JAMA Pediatr 2023;177:1073-84.
2. Chiwandire N, Jassat W, Groome M, et al. Changing epidemiology of COVID-19 in children and adolescents over four successive epidemic waves in South Africa, 2020-2022. Journal of the Pediatric Infectious Diseases Society 2023;12:128-34.
3. DeCuir J, Payne AB, Self WH, et al. Interim effectiveness of updated 2023-2024 (Monovalent XBB.1.5) COVID-19 vaccines against COVID-19-associated emergency department and urgent care encounters and hospitalization among immunocompetent adults aged ≥18 years - VISION and IVY Networks, September 2023-January 2024. MMWR. Morbidity and Mortality Weekly Report 2024;73:180-8.
4. Tartof SY, Slezak JM, Puzniak L, et al. Effectiveness of BNT162b2 XBB Vaccine Against XBB and JN.1 Sublineages. Open Forum Infectious Diseases 2024;11:ofae370.
5. Liu B, Stepien S, Dobbins T, et al. Effectiveness of COVID-19 vaccination against COVID-19 specific and all-cause mortality in older Australians: a population based study. Lancet Reg Health West Pac 2023;40:100928.
6. Inacio MC, Davies L, Jorissen R, et al. Excess mortality in residents of aged care facilities during COVID-19 in Australia, 2019-22. International Journal of Epidemiology 2024;53.
7. Nafilyan V, Ward IL, Robertson C, Sheikh A, Consortium NCSIB. Evaluation of risk factors for postbooster Omicron COVID-19 deaths in England. JAMA Network Open 2022;5:e2233446-e.
8. Fericean RM, Oancea C, Reddyreddy AR, et al. Outcomes of elderly patients hospitalized with the SARS-CoV-2 Omicron B.1.1.529 variant: a systematic review. Int J Environ Res Public Health 2023;20.
9. Taylor CA, Patel K, Pham H, et al. COVID-19-associated hospitalizations among U.S. adults aged ≥18 years - COVID-NET, 12 states, October 2023-April 2024. MMWR. Morbidity and Mortality Weekly Report 2024;73:869-75.
10. Khan N, Mahmud N. Effectiveness of SARS-CoV-2 Vaccination in a Veterans Affairs Cohort of Patients With Inflammatory Bowel Disease With Diverse Exposure to Immunosuppressive Medications. Gastroenterology 2021;161:827-36.
11. Aslam S, Adler E, Mekeel K, Little SJ. Clinical effectiveness of COVID-19 vaccination in solid organ transplant recipients. Transpl Infect Dis 2021;23:e13705.
12. Monin L, Laing AG, Muñoz-Ruiz M, et al. Safety and immunogenicity of one versus two doses of the COVID-19 vaccine BNT162b2 for patients with cancer: interim analysis of a prospective observational study. The Lancet Oncology 2021;22:765-78.
13. Herishanu Y, Avivi I, Aharon A, et al. Efficacy of the BNT162b2 mRNA COVID-19 vaccine in patients with chronic lymphocytic leukemia. Blood 2021;137:3165-73.
14. Goshen-Lago T, Waldhorn I, Holland R, et al. Serologic status and toxic effects of the SARS-CoV-2 BNT162b2 vaccine in patients undergoing treatment for cancer. JAMA Oncol 2021;7:1507-13.
15. Boyarsky BJ, Werbel WA, Avery RK, et al. Antibody response to 2-dose SARS-CoV-2 mRNA vaccine series in solid organ transplant recipients. JAMA 2021;325:2204-6.
16. Redjoul R, Le Bouter A, Beckerich F, Fourati S, Maury S. Antibody response after second BNT162b2 dose in allogeneic HSCT recipients. The Lancet 2021;398:298-9.
17. Jena A, Mishra S, Deepak P, et al. Response to SARS-CoV-2 vaccination in immune mediated inflammatory diseases: Systematic review and meta-analysis. Autoimmun Rev 2022;21:102927.
18. Arnold J, Winthrop K, Emery P. COVID-19 vaccination and antirheumatic therapy. Rheumatology 2021;60:3496-502.
19. Hagin D, Freund T, Navon M, et al. Immunogenicity of Pfizer-BioNTech COVID-19 vaccine in patients with inborn errors of immunity. Journal of Allergy and Clinical Immunology 2021;148:739-49.
20. Woldemeskel BA, Karaba AH, Garliss CC, et al. The BNT162b2 mRNA vaccine elicits robust humoral and cellular immune responses in people living with human immunodeficiency virus (hiv). Clinical Infectious Diseases 2022;74:1268-70.
21. Frater J, Ewer KJ, Ogbe A, et al. Safety and immunogenicity of the ChAdOx1 nCoV-19 (AZD1222) vaccine against SARS-CoV-2 in HIV infection: a single-arm substudy of a phase 2/3 clinical trial. Lancet HIV 2021;8:e474-e85.
22. Benotmane I, Gautier G, Perrin P, et al. Antibody response after a third dose of the mRNA-1273 SARS-CoV-2 vaccine in kidney transplant recipients with minimal serologic response to 2 doses. JAMA 2021;326:1063-5.
23. Connolly CM, Teles M, Frey S, et al. Booster-dose SARS-CoV-2 vaccination in patients with autoimmune disease: a case series. Annals of the Rheumatic Diseases 2022;81:291-3.
24. Ducloux D, Colladant M, Chabannes M, Yannaraki M, Courivaud C. Humoral response after 3 doses of the BNT162b2 mRNA COVID-19 vaccine in patients on hemodialysis. Kidney International 2021;100:702-4.
25. Hall VG, Ferreira VH, Ku T, et al. Randomized trial of a third dose of mRNA-1273 vaccine in transplant recipients. New England Journal of Medicine 2021;385:1244-6.
26. Whitaker HJ, Tsang RSM, Byford R, et al. Pfizer-BioNTech and Oxford AstraZeneca COVID-19 vaccine effectiveness and immune response amongst individuals in clinical risk groups. Journal of Infection 2022;84:675-83.
27. Villar J, Conti CPS, Gunier RB, et al. Pregnancy outcomes and vaccine effectiveness during the period of omicron as the variant of concern, INTERCOVID-2022: a multinational, observational study. The Lancet 2023;401:447-57.
28. Piekos SN, Hwang YM, Roper RT, et al. Effect of COVID-19 vaccination and booster on maternal-fetal outcomes: a retrospective cohort study. Lancet Digit Health 2023;5:e594-e606.
29. Chmielewska B, Barratt I, Townsend R, et al. Effects of the COVID-19 pandemic on maternal and perinatal outcomes: a systematic review and meta-analysis. Lancet Glob Health 2021;9:e759-e72.
30. Birol Ilter P, Prasad S, Berkkan M, et al. Clinical severity of SARS-CoV-2 infection among vaccinated and unvaccinated pregnancies during the Omicron wave. Ultrasound in Obstetrics and Gynecology 2022;59:560-2.
31. Floyd R, Hunter S, Murphy N, Lindow SW, O'Connell MP. A retrospective cohort study of pregnancy outcomes during the pandemic period of the SARS-CoV-2 omicron variant: a single center's experience. International Journal of Gynaecology and Obstetrics 2022;159:605-6.
32. Halasa NB, Olson SM, Staat MA, et al. Maternal vaccination and risk of hospitalization for Covid-19 among infants. New England Journal of Medicine 2022;387:109-19.
33. Jorgensen SC, Hernandez A, Fell DB, et al. Maternal mRNA covid-19 vaccination during pregnancy and delta or omicron infection or hospital admission in infants: test negative design study. BMJ 2023;380.
34. Danino D, Ashkenazi-Hoffnung L, Diaz A, et al. Effectiveness of BNT162b2 vaccination during pregnancy in preventing hospitalization for Severe Acute Respiratory Syndrome Coronavirus 2 in infants. Journal of Pediatrics 2023;254:48-53.
35. Kirsebom FCM, Andrews N, Mensah AA, et al. Vaccine effectiveness against mild and severe disease in pregnant mothers and their infants in England. medRxiv 2023:2023.06.07.23290978.
36. Altarawneh HN, Chemaitelly H, Ayoub HH, et al. Effects of previous infection and vaccination on symptomatic Omicron infections. New England Journal of Medicine 2022;387:21-34.
37. Lazarus R, Baos S, Cappel-Porter H, et al. Safety and immunogenicity of concomitant administration of COVID-19 vaccines (ChAdOx1 or BNT162b2) with seasonal influenza vaccines in adults in the UK (ComFluCOV): a multicentre, randomised, controlled, phase 4 trial. The Lancet 2021;398:2277-87.
38. Izikson R. Phase II, open-label study to assess the safety and immunogenicity of Fluzone® High-Dose Quadrivalent (Influenza Vaccine), 2021–2022 Formulation and a third dose of mRNA-1273 COVID-19 vaccine (Moderna) administered either concomitantly or singly in adults 65 years of age and older previously vaccinated with a 2-dose schedule of mRNA-1273 vaccine.  2021.
39. Janssen C, Mosnier A, Gavazzi G, et al. Coadministration of seasonal influenza and COVID-19 vaccines: a systematic review of clinical studies. Human Vaccines & Immunotherapeutics 2022;18:2131166.
40. United States Food and Drug Administration. Vaccines and Related Biological Products Advisory Committee Meeting June 15, 2022, FDA Briefing Document: EUA amendment request for Pfizer-BioNTech COVID-19 Vaccine for use in children 6 months through 4 years of age. 2022. (Accessed 30 March 2023). Published online June 15, 2022 2022. https://www.fda.gov/media/159195/download
41. Walter EB, Talaat KR, Sabharwal C, et al. Evaluation of the BNT162b2 Covid-19 vaccine in children 5 to 11 years of age. New England Journal of Medicine 2022;386:35-46.
42. Gayed J, Diya O, Lowry FS, et al. Safety and immunogenicity of the monovalent Omicron XBB.1.5-adapted BNT162b2 COVID-19 vaccine in individuals ≥12 years old: A phase 2/3 trial. Vaccines (Basel) 2024;12.
43. Maltezou HC, Anastassopoulou C, Hatziantoniou S, Poland GA, Tsakris A. Anaphylaxis rates associated with COVID-19 vaccines are comparable to those of other vaccines. Vaccine 2022;40:183-6.
44. Australian Government Department of Health and Aged Care Therapeutic Goods Administration. COVID-19 vaccine safety report - 23-03-2023. 2023. (Accessed 25 March 2023). https://www.tga.gov.au/news/covid-19-vaccine-safety-reports/covid-19-vaccine-safety-report-23-03-2023#myocarditis-and-pericarditis-after-covid19-vaccination
45. Rout A, Suri S, Vorla M, Kalra DK. Myocarditis associated with COVID-19 and its vaccines-a systematic review. Progress in Cardiovascular Diseases 2022.
46. Shimabukuro TT, Kim SY, Myers TR, et al. Preliminary findings of mRNA Covid-19 vaccine safety in pregnant persons. New England Journal of Medicine 2021;384:2273-82.
47. Sadarangani M, Soe P, Shulha HP, et al. Safety of COVID-19 vaccines in pregnancy: a Canadian National Vaccine Safety (CANVAS) network cohort study. The Lancet Infectious Diseases 2022;22:1553-64.
48. Moro PL, Olson CK, Clark E, et al. Post-authorization surveillance of adverse events following COVID-19 vaccines in pregnant persons in the Vaccine Adverse Event Reporting System (VAERS), December 2020–october 2021. Vaccine 2022;40:3389-94.
49. Ai-ris YC, McMahan K, Yu J, et al. Immunogenicity of COVID-19 mRNA vaccines in pregnant and lactating women. JAMA 2021;325:2370-80.
50. Gray KJ, Bordt EA, Atyeo C, et al. Coronavirus disease 2019 vaccine response in pregnant and lactating women: a cohort study. American Journal of Obstetrics and Gynecology 2021;225:303. e1-. e17.
51. Dhama K, Khan S, Tiwari R, et al. Coronavirus disease 2019–COVID-19. Clinical Microbiology Reviews 2020;33:10.1128/cmr. 00028-20.
52. Al-Tawfiq JA, Chu D-T, Hoang V-T, Memish ZA. From pandemicity to endemicity: the journey of SARS-CoV-2. Journal of Epidemiology and Global Health 2022;12:147-9.
53. Liu X, Huang J, Li C, et al. The role of seasonality in the spread of COVID-19 pandemic. Environmental Research 2021;195:110874.
54. D'Amico F, Marmiere M, Righetti B, et al. COVID-19 seasonality in temperate countries. Environmental Research 2022;206:112614.
55. World Health Organization. Tracking SARS-CoV-2 variants. 2023. https://www.who.int/activities/tracking-SARS-CoV-2-variants
56. World Health Organization. Statement on the antigen composition of COVID-19 vaccines. 2023. (Accessed 18 May 2023). https://www.who.int/news/item/18-05-2023-statement-on-the-antigen-composition-of-covid-19-vaccines
57. Lamers MM, Haagmans BL. SARS-CoV-2 pathogenesis. Nature Reviews Microbiology 2022;20:270-84.
58. Fericean RM, Oancea C, Reddyreddy AR, et al. Outcomes of elderly patients hospitalized with the SARS-CoV-2 Omicron B. 1.1. 529 variant: A systematic review. International Journal of Environmental Research and Public Health 2023;20:2150.
59. Genç Bahçe Y, Acer Ö, Özüdoğru O. Effectiveness of inactivated and mRNA COVID-19 vaccines against SARS-CoV-2 infection, severe disease and mortality in the geriatric population. Current Microbiology 2023;80:206.
60. Zhang JJ, Dong X, Liu GH, Gao YD. Risk and protective factors for COVID-19 morbidity, severity, and mortality. Clinical Reviews in Allergy and Immunology 2023;64:90-107.
61. Liu B, Spokes P, He W, Kaldor J. High risk groups for severe COVID-19 in a whole of population cohort in Australia. BMC Infectious Diseases 2021;21:1-9.
62. Allotey J, Fernandez S, Bonet M, et al. Clinical manifestations, risk factors, and maternal and perinatal outcomes of coronavirus disease 2019 in pregnancy: living systematic review and meta-analysis. BMJ 2020;370.
63. Stock SJ, Moore E, Calvert C, et al. Pregnancy outcomes after SARS-CoV-2 infection in periods dominated by delta and omicron variants in Scotland: a population-based cohort study. The Lancet Respiratory Medicine 2022;10:1129-36.
64. Meyerowitz EA, Richterman A, Gandhi RT, Sax PE. Transmission of SARS-CoV-2: a review of viral, host, and environmental factors. Annals of Internal Medicine 2021;174:69-79.
65. Esper FP, Adhikari TM, Tu ZJ, et al. Alpha to Omicron: disease severity and clinical outcomes of major SARS-CoV-2 variants. The Journal of Infectious Diseases 2023;227:344-52.
66. Harrigan SP, Wilton J, Chong M, et al. Clinical severity of severe acute respiratory syndrome coronavirus 2 Omicron variant relative to Delta in British Columbia, Canada: a retrospective analysis of whole-genome sequenced cases. Clinical Infectious Diseases 2023;76:e18-e25.
67. Wu Y, Kang L, Guo Z, et al. Incubation Period of COVID-19 Caused by Unique SARS-CoV-2 Strains: A Systematic Review and Meta-analysis. JAMA Netw Open 2022;5:e2228008.
68. Erikstrup C, Laksafoss AD, Gladov J, et al. Seroprevalence and infection fatality rate of the SARS-CoV-2 Omicron variant in Denmark: A nationwide serosurveillance study. Lancet Reg Health Eur 2022;21:100479.
69. Raisi-Estabragh Z, Cooper J, Salih A, et al. Cardiovascular disease and mortality sequelae of COVID-19 in the UK Biobank. Heart 2022;109:119-26.
70. Xu E, Xie Y, Al-Aly Z. Long-term neurologic outcomes of COVID-19. Nature Medicine 2022;28:2406-15.
71. Taquet M, Sillett R, Zhu L, et al. Neurological and psychiatric risk trajectories after SARS-CoV-2 infection: an analysis of 2-year retrospective cohort studies including 1 284 437 patients. Lancet Psychiatry 2022;9:815-27.
72. Terpos E, Ntanasis-Stathopoulos I, Elalamy I, et al. Hematological findings and complications of COVID-19. American Journal of Hematology 2020;95:834-47.
73. Zacharias H, Dubey S, Koduri G, D'Cruz D. Rheumatological complications of Covid 19. Autoimmun Rev 2021;20:102883.
74. Michelen M, Manoharan L, Elkheir N, et al. Characterising long COVID: a living systematic review. BMJ global health 2021;6:e005427.
75. O'Mahoney LL, Routen A, Gillies C, et al. The prevalence and long-term health effects of Long Covid among hospitalised and non-hospitalised populations: A systematic review and meta-analysis. EClinicalMedicine 2023;55.
76. Tsampasian V, Elghazaly H, Chattopadhyay R, et al. Risk factors associated with Post− COVID-19 condition: a systematic review and meta-analysis. JAMA Internal Medicine 2023.
77. Australian COVID-19 Serosurveillance Network. Seroprevalence of SARS-CoV-2-Specific Antibodies among Australian Blood Donors: Round 4 Update. 2023. https://www.kirby.unsw.edu.au/sites/default/files/documents/COVID19-Blood-Donor-Report-Round4-Nov-Dec-2022%5B1%5D.pdf
78. Australian COVID-19 Serosurveillance Network. Paediatric SARS-CoV-2 Serosurvey 2022, Australia Summary Report. 2022. https://ncirs.org.au/sites/default/files/2022-11/PAEDS%20NCIRS_COVID-19%20Paediatric%20Serosurvey%202022%20Report_3-11-2022_Final_1.pdf
79. Kirsebom FCM, Stowe J, Lopez Bernal J, Allen A, Andrews N. Effectiveness of autumn 2023 COVID-19 vaccination and residual protection of prior doses against hospitalisation in England, estimated using a test-negative case-control study. Journal of Infection 2024;89:106177.
80. Happle C, Hoffmann M, Kempf A, et al. Humoral immunity after mRNA SARS-CoV-2 omicron JN.1 vaccination. The Lancet Infectious Diseases 2024.
81. van Werkhoven CH, Valk AW, Smagge B, et al. Early COVID-19 vaccine effectiveness of XBB.1.5 vaccine against hospitalisation and admission to intensive care, the Netherlands, 9 October to 5 December 2023. Euro Surveill 2024;29.
82. Hansen CH, Moustsen-Helms IR, Rasmussen M, et al. Short-term effectiveness of the XBB.1.5 updated COVID-19 vaccine against hospitalisation in Denmark: a national cohort study. The Lancet Infectious Diseases 2024;24:e73-e4.
83. Modjarrad K. ACIP meeting slides. Pfizer-BioNTech 2023 – 2024 COVID-19 vaccine. Advisory Committee on Immunization Practices; 12 September 2023; Atlanta.
84. Stankov MV, Hoffmann M, Gutierrez Jauregui R, et al. Humoral and cellular immune responses following BNT162b2 XBB.1.5 vaccination. The Lancet Infectious Diseases 2024;24:e1-e3.
85. Australian Government Department of Health and Aged Care Therapeutic Goods Administration. AUSTRALIAN PRODUCT INFORMATION – COMIRNATY® (tozinameran) COVID-19 VACCINE [Tris/Sucrose Presentation]. 2023. https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2021-PI-02442-1
86. Australian Government Department of Health and Aged Care. National vaccine storage guidelines: Strive for 5. 3rd ed. Canberra: Australian Government Department of Health and Ageing; 2019. https://www.health.gov.au/resources/publications/national-vaccine-stora…;