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 illness or death from COVID-19.

Who

COVID-19 vaccination is recommended for all people aged 5 years and older. It is also recommended for children aged 6 months to 5 years with one of the following conditions:

• Severe immunocompromise 
• Disability with complex care requirements
• Complex and/or multiple medical conditions that increase the risk of severe COVID-19

How

Primary course vaccination is recommended for all people aged 5 years or older, and for children aged 6 months to 5 years in a specified risk group. 

Most people require 2 doses for their primary course. People with severe immunocompromise require 3 doses. 

Further doses are recommended or can be considered based on an individual’s age and presence of risk factors for severe illness.

Why

The COVID-19 pandemic has caused millions of deaths globally. Vaccination reduces the risk of severe illness 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 Omicron XBB.1.5 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.

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.^8-10 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.

An Omicron XBB.1.5-containing vaccine is preferred to complete a primary course in people aged 5 years or older who have started with a different formulation. If possible, the primary course should be completed using the XBB.1.5 formulation of the same brand. Where this is not possible, other age-appropriate vaccine brands and formulations are acceptable.

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 

Evidence supports the safety, immunogenicity and efficacy of mixed schedules. Short-term adverse events are slightly more likely to occur in people who have a mixed schedule, but the nature and severity of the adverse events appears similar to single brand schedules.^11-17 Currently there are limited data on the safety and immunogenicity of mixed primary schedules incorporating Nuvaxovid, but where an mRNA vaccine is contraindicated, there are no theoretical safety concerns about using Nuvaxovid.

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 is >12 weeks. 

Mixed schedules for children who turn 6 or 12 between doses

Children who turn 6 or 12 between doses should receive the appropriate brand and dose for their age on the day of vaccination. For example, a child who turns 6 after receiving the first dose of Comirnaty Original 6 months – <5 years formulation should receive Comirnaty Omicron XBB.1.5 5 – <12 years formulation (light blue cap) for the second dose, and a child who turns 12 after a first dose of Comirnaty Omicron XBB.1.5 5 – <12 years formulation (light blue cap) or Comirnaty Original 5 - <12 years formulation should receive an Omicron XBB.1.5-based formulation registered for use in people aged ≥12 years for their second dose. 

Administration errors

For detailed information refer to the ATAGI clinical guidance on COVID-19 vaccine administration errors.
 

Contraindications

General contraindications which apply to all COVID-19 vaccines are:

Anaphylaxis to vaccine components

• documented anaphylaxis after a previous dose of a COVID-19 vaccine from the same class, e.g., anaphylaxis after one mRNA COVID-19 vaccine is a contraindication to all other mRNA COVID-19 vaccines
• documented anaphylaxis after any component of that COVID-19 vaccine, e.g., Comirnaty and Spikevax vaccines would be contraindicated in someone with anaphylaxis to polyethylene glycol (PEG), and Nuvaxovid would be contraindicated in someone with anaphylaxis to polysorbate 80 

 Serious adverse event recognised as vaccine-related and assessed as likely to recur with future doses

This includes:

• any other serious adverse event attributed to a previous dose of a COVID-19 vaccine that has been reported to state/territory adverse event reporting programs and/or the TGA

AND

• has been determined following review by, and/or on the opinion of, an experienced immunisation provider/medical specialist to be a contraindication to future doses based on a risk of recurrence with repeat vaccine doses.

Precautions

Specific allergies

The following people should be assessed to check they are suitable for vaccination:

• people with immediate (within 4 hours) and generalised symptoms of a possible allergic reaction (such as urticaria/hives) to a previous dose of a COVID-19 vaccine, without anaphylaxis
• people with a generalised allergic reaction (without anaphylaxis) to any component of the COVID-19 vaccine to be administered 
• people with a history of anaphylaxis to a previous vaccine or drug (injectable or oral) where a common component such as PEG (for mRNA vaccines) or polysorbate 80 (for Nuvaxovid) may have been the cause
• people with a history of confirmed mastocytosis with recurrent anaphylaxis that requires treatment.

Assessment may be done in consultation with an allergist/immunologist or specialist immunisation clinic.

People in these categories may need one or more of the following:

• to be vaccinated in a facility with capacity to manage acute anaphylaxis
• to be observed for at least 30 minutes following administration of a COVID-19 vaccine dose
• to be vaccinated with an alternative brand of COVID-19 vaccine.

Refer to ASCIA Guide: Allergy and COVID-19 Vaccination for more information.

People with a suspected allergy to a previous dose

People who are suspected to have had an allergic reaction to their first dose of a COVID-19 vaccine should seek advice from the state/territory specialist immunisation service or a specialist allergist/immunologist. These people may need a clinical assessment before the second vaccine dose.

Before and during each vaccination session, check that up-to-date protocols, equipment, medicines and staff trained to manage anaphylaxis are available. 

Refer to Preparing an anaphylaxis response kit.

Cardiac precautions

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.

For more information, refer to the Joint ATAGI-CSANZ Guidance on Myocarditis and/or Pericarditis after COVID-19 Vaccines. 
 

Adverse events after Comirnaty Original

Children aged 6 months - <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%).¹⁸ 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.¹⁸ 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%).¹⁹ Fever occurred in 3% of children after the first dose and 6.5% of children after the second dose. 

Adverse events after Comirnaty bivalent Original/Omicron BA.1

The most commonly reported local and systemic adverse events following a second booster dose of Comirnaty bivalent Original/Omicron BA.1 in adults aged > 55 years were injection site pain (in about 60%), fatigue (in about 50%), headache (in about 35%) and muscle pain (in about 20%).²⁰ 

Adverse events after Comirnaty bivalent Original/Omicron BA.4/5

The most commonly reported local and systemic adverse events in the clinical trial were injection site pain (in about 70%), fatigue (in about 55%), headache (in about 40%) and muscle pain (in about 25%).²¹ The suggestion of an increased risk of ischaemic stroke in adults aged ≥ 65 years following receipt of Comirnaty bivalent Original/Omicron BA.4/5 has emerged from a single US safety surveillance system, but has not been validated by other analyses in the USA and other countries.^22,23 Currently, this is not considered to be a true clinical risk.²⁴ 

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.

Adverse events after Spikevax Original 6 months - < 5 years

In children aged 6 – 23 months, the most frequent solicited adverse events reported in the clinical trial were irritability (in about 65%), sleepiness (in about 35%) and loss of appetite (in about 30%).²⁵ Fever occurred in 11% of children after the first dose and about 15% after the second dose. 

In children aged 24 - ≤ 36 months, the most frequent solicited adverse events were irritability (in about 55%), sleepiness (in about 30-35%) and loss of appetite (in about 25-30%).²⁵ Fever occurred in about 11% of children after the first dose and about 20% after the second dose. 

In children aged 37 months to < 6 years, the most frequent solicited adverse events were fatigue (in about 40-50%) and headache (in about 10-15%).²⁵ Fever occurred in 7.7% after the first dose and 16% after the second dose. 

Adverse events after Spikevax bivalent Original/Omicron BA.4/5

The most frequent adverse reactions reported after a booster dose of Spikevax bivalent Original/Omicron BA.4/5 were injection site pain (in about 82%), fatigue (in about 60%), headache (in about 50%), muscle pain (in about 45%), joint pain (in about 35%) and axillary swelling or tenderness in about 20%.²¹  

Adverse events after Spikevax Omicron XBB.1.5

Local and systemic reactions following the Spikevax XBB.1.5 vaccine occurred at similar or lower rates compared to the original and bivalent (original/BA.4/5) Spikevax formulations.²⁶ The most frequent adverse events reported were injection site pain (in about 68%), fatigue (in about 44%), muscle pain (in about 38%), and headache (in about 34%).²⁶

Adverse events after Nuvaxovid 

The most frequent adverse events reported after Nuvaxovid in the clinical trial were injection site tenderness (75%), injection site pain (53%), muscle pain (51%), headache (50%), malaise (41%), joint pain (24%) and nausea or vomiting (15%).²⁷ Adverse events occurred at a similar frequency in adolescents aged 12-17 years and in adults aged ≥ 18 years. 

Nuvaxovid has been associated with myocarditis and pericarditis following vaccination.²⁸ Refer to ATAGI Guidance on myocarditis and pericarditis after COVID-19 vaccines for further information.

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.²⁹ The rate of anaphylaxis after Nuvaxovid is not yet known.

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 (Comirnaty or Spikevax), although cases have been reported in male and female adults of all ages and after any dose of a COVID-19 vaccine.^28,30 

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 about when to seek medical attention. For more information, including reporting rates for individual vaccines, refer to ATAGI Guidance on myocarditis and pericarditis after COVID-19 vaccines, and the Therapeutic Goods Administration COVID-19 vaccine safety reports.

Safety of COVID-19 vaccines during pregnancy or breastfeeding

mRNA COVID-19 vaccines are safe and effective in pregnancy.^31-33 Less is known about the safety of Nuvaxovid in pregnant or breastfeeding women, however there are no known or theoretical safety concerns.

The adverse event profile of pregnant women is similar to that of non-pregnant women following vaccination with a monovalent (Original) mRNA COVID-19 vaccine.^34,35 Pregnant women are slightly more likely to report injection site pain, and less likely to report generalised symptoms such as fever or tiredness. 

For further information refer to the ATAGI Shared decision making guide for women who are pregnant, breastfeeding or planning pregnancy. 
 

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.³⁶ 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.

In late-2023, Omicron is the only variant currently circulating globally.³⁷ Previous variants of concern (e.g. Alpha, Beta, Gamma, Delta) and the ancestral strain have largely disappeared. Numerous sub-lineages of Omicron have since caused distinct global waves of infection, e.g. BA.2, BA.4/5, XBB (a recombinant of BA.2.10.1 and BA.2.75) and other recombinant sub-lineages, and BQ.1 (a sub-lineage of BA.5).³⁸

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.³⁹

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.^40,41 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 50.⁴⁰ 

Medical conditions 

Medical conditions also independently increase the risk of severe disease but to a lesser extent than age.⁴² For a list of these conditions see List. Risk conditions for severe COVID-19.

Pregnancy

Unvaccinated pregnant women with COVID-19 have an increased risk of severe illness compared with unvaccinated non-pregnant women of reproductive age with COVID-19.⁴³ This risk appears to be substantially reduced during the Omicron period in women who have received 3 doses of vaccine.¹ 

Transmission

SARS-CoV-2 is spread via respiratory droplets or aerosols generated through breathing, talking or coughing.⁴⁴ 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.⁴⁵ 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 illness 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.⁴⁶

The incubation period after exposure to SARS-CoV-2 (Omicron) is most commonly 3 days, but can be up to 14 days.⁴⁷ 

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 (CI: 5·1–7·5) per 100 000 infections.⁴⁸

A range of metabolic, cardiovascular, respiratory, immunological and neurological sequelae following COVID-19 have been reported in the literature.^49-53 

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.⁵⁴ 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.⁵⁵ 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.⁵⁶

Vaccinated people have a significantly lower risk of post-COVID-19 condition (OR, 0.57; 95% CI, 0.43-0.76).⁵⁶ 

COVID-19 disease in Australia

Serosurveys indicate that an increasingly large proportion of the 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.⁵⁷ Similarly, approximately 80% of unvaccinated children had COVID-19 by August 2022.⁵⁸

COVID-19 is likely to continue globally as an endemic disease with fluctuating incidence driven by waning population vaccine- and infection-related immunity, virus mutation leading to new SARS-CoV-2 variants with immune escape, and seasonal factors.^59-61 
 

Original vaccines are directed at, or contain, the ancestral spike protein only. Omicron-based vaccines have also been developed. Currently available monovalent Omicron XBB.1.5 vaccines are formulated against the Omicron XBB.1.5 subvariant. Currently available bivalent mRNA vaccines are formulated against both ancestral and Omicron strains (currently either the BA.1 or BA.4/5 Omicron sub-variants). Currently people <5 years can only access Original/ancestral based vaccines, while people aged ≥5 years can access both Original/ancestral and Omicron-based vaccines.

Omicron-based COVID-19 vaccines

There are limited direct data on the immunogenicity or efficacy of Omicron-based vaccines for primary course vaccination. Their preferential use for the primary course is based on the superior immunogenicity and vaccine effectiveness of bivalent vaccines against Omicron sub-variants, when evaluated as further doses. 

XBB.1.5 vaccine effectiveness

As of late 2023, there are no direct data on the vaccine effectiveness of Omicron XBB.1.5 vaccines for use as primary or further doses. The recommendations for their use are based on the superior vaccine effectiveness of bivalent vaccines against Omicron sub-variants when evaluated as further doses. 

XBB.1.5 vaccine immunogenicity 

Spikevax Omicron XBB.1.5 immunogenicity 

Early human immunogenicity data demonstrate an 8.7-10.4 times increase in neutralising antibodies against the Omicron XBB.1.5 subvariant and other recently circulating subvariants at 29 days after receiving a dose of the Moderna monovalent XBB.1.5 vaccine in people who had completed at least a primary course of vaccination.²⁶

Comirnaty Omicron XBB.1.5 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.⁶² 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.⁶²

Bivalent vaccine effectiveness

Vaccine effectiveness studies demonstrate that both BA.4/5-based and BA.1-based bivalent vaccines offer excellent protection against hospitalisation and death from COVID-19 for several months. 

A population-wide cohort study conducted across 4 Nordic countries during an Omicron-dominant study period reported the combined vaccine effectiveness (CVE) of Pfizer and Moderna BA.1 vaccines against hospitalisation at 74% (95% CI: 68.6 – 79.4%), and of BA.4/5 vaccines at 80.5% (95% CI: 69.5 – 91.5%).⁶³ 

Similarly, the effectiveness of Pfizer or Moderna BA.4/5 vaccines against hospitalisation or death during an Omicron-dominant period was estimated at 61.8% (95% CI: 48.2 - 71.8) in a US test-negative case control study. In this latter study, VE estimates of Pfizer and Moderna BA.4/5 vaccines were similar (63.8% vs 60.4% respectively).⁶⁴  

Data from the UK Health Security Agency in people aged ≥50 years demonstrate some waning of the incremental protection from BA.1 booster doses. At 2 to 4  weeks post booster, VE against hospitalisation for Pfizer BA.1 vaccine was 47.2% (95% CI: 39.4–51.1%) and for Moderna BA.1 vaccine was 57.8% (95% CI: 51.6–63.3%), dropping to 38.0% (95% CI: 31–44.3%) and 34.1% (95% CI: 29.2–38.7%) respectively at 10+ weeks.⁶⁵

Bivalent vaccines also offer some protection against symptomatic infection. An observational study in Japan conducted during a BA.5- dominant period found that the effectiveness of BA.4/5 and BA.1 vaccines against symptomatic illness was similar. Combined VE of Pfizer and Moderna BA.1 vaccines was 65% (95% CI: 47 – 77) for BA.1, and combined VE of Pfizer and Moderna BA.4/5 vaccines was 76% (95% CI: 65 – 83).⁶⁶

Bivalent vaccine immunogenicity

Comirnaty Original/Omicron BA.4/5

Adults aged over 55 who received Comirnaty Original/Omicron BA.4/5 as a second booster developed higher neutralising antibody titres against the BA.4/5 sub-variants when compared with adults from an older study where Comirnaty Original was given as a second booster (geometric mean ratio 2.91, 95% CI: 2.45 – 3.44).⁶⁷ Neutralisation of BA.1.1 and XBB.1 subvariants was also higher with the BA.4/5-based bivalent booster than with the original formulation. The BA.4/5-based booster induced non-inferior and modestly higher titres for ancestral strain neutralisation (GMR 1.38, 95%CI: 1.22 – 1.56), noting the comparison was conducted between non-contemporaneous cohorts. Other age groups showed similar trends (12-17 years; 18-55 years).

Comirnaty Original/Omicron BA.1

Adults aged over 55 who received Comirnaty Original/Omicron BA.1 as a second booster developed higher neutralising antibody titres against the BA.1 sub-variant when compared to those who received a second booster dose of Comirnaty Original in the same study (GMR 1.56, 95% CI 1.17 – 2.08).⁶⁸ The BA.1-based booster induced similar neutralising antibody titres against the ancestral virus compared with Comirnaty Original (GMR 0.99; 95% CI 0.82 – 1.20).

Immunogenicity data are not available for Comirnaty Original/Omicron BA.1 in people aged 55 years and under, however a monovalent BA.1 candidate vaccine was evaluated in people aged 18-55 years. 263 participants received a monovalent BA.1 candidate vaccine as a booster dose, and 280 received a booster dose of Comirnaty Original.⁶⁹ Neutralising antibody titres against the Omicron BA.1 sub-variant were higher in those who received the BA.1-based vaccine compared with those who received Comirnaty Original. These data were used to infer protection from a bivalent BA.1 booster vaccine in this age group.

Spikevax bivalent Original/Omicron BA.4/5

A clinical trial reported 5.1-6.3 times greater neutralising antibody levels against the BA.4/5 Omicron subvariants at 1 month after a booster dose of Spikevax bivalent Original/Omicron BA.4/5 compared with Spikevax Original in adults aged 18 years and older.⁷⁰

Original COVID-19 vaccines

Comirnaty Original

In children aged 5 to 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.¹⁹ 

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.¹⁸ 

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 to 11 years who had no evidence of past infection.⁷⁰

Nuvaxovid (Novavax)

The clinical trial evaluating Nuvaxovid for primary vaccination was conducted prior to the emergence of the Omicron variant of SARS-CoV-2. Nuvaxovid has been shown to have high efficacy in two clinical trials conducted in the United States, Mexico and the United Kingdom during periods when the Alpha variant was predominant. Vaccine efficacy against PCR-confirmed symptomatic COVID-19 in serologically negative adults after 2 doses was approximately 90%.^71,72 A third study from South Africa where higher numbers of infection occurred from the Beta variant, vaccine efficacy among HIV-negative adults was 60.1% (95% CI: 19.9–80.1) overall.⁷³

In adolescents aged 12 to 17 years without evidence of previous SARS-CoV-2 infection, Nuvaxovid was 79.5% effective (95% CI: 46.8–92.1) at preventing laboratory-confirmed symptomatic COVID-19, from a clinical trial during a period of Delta variant predominance.²⁷ Neutralising antibody titres after 2 doses in adolescents aged 12 to 17 years were comparable to those observed trial participants aged 18 to 25 years.²⁷ 

A randomised controlled trial showed that a booster of Nuvaxovid increased anti spike IgG antibody levels by 4.5-4.7 times after Comirnaty primary vaccination, but fold increases and absolute titres were lower than those seen after Comirnaty booster (6.8-10.2 times after Comirnaty primary).⁷⁴
 

Most COVID-19 vaccines are currently presented as multi-dose vials and require special handling to maintain viability and sterility. For additional information on multidose vials see Administration of vaccines and ATAGI guidance on the use of multi-dose vials for COVID-19 vaccination.

mRNA vaccines are required to be stored frozen at ultra-cold temperatures but once thawed can be stored for certain periods at 2°C to 8°C in a refrigerator before use. Requirements differ by vaccine brand and vial.

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 more information, see the National Vaccine Storage Guidelines Strive for 5.⁷⁵

Comirnaty Original paediatric formulations

The following guidance applies to:

• Comirnaty Original 6 months - <5 years formulation (maroon cap)
• Comirnaty Original 5 - <12 years formulation (orange cap)

Comirnaty Original paediatric formulations require storage at –90°C to –60°C. It can be thawed and stored at 2°C to 8°C with a shelf life of 10 weeks. Undiluted vaccine vials can be stored at 8-30°C for 24 hours.

Comirnaty Original 6 months - <5 years formulation (maroon cap) is supplied as a multi-dose vial containing 0.4 mL of concentrated suspension for injection vaccine. It must be reconstituted by diluting 2.2 mL of sterile 0.9% sodium chloride. Do not use bacteriostatic 0.9% sodium chloride. The total quantity after dilution will be 2.6mL. Each vial contains 10 doses of 0.2mL of vaccine.

Comirnaty Original 5 - <12 years formulation (orange cap) is supplied as a multi-dose vial containing 1.3 mL of concentrated suspension for injection vaccine. It must be reconstituted by diluting with 1.3 mL of sterile 0.9% sodium chloride. Do not use bacteriostatic 0.9% sodium chloride. The total quantity after dilution will be 2.6 mL. Each vial contains 10 doses of 0.2mL of vaccine. 

Low dead-volume syringes and/or needles should be used in order to extract 10 doses from a single vial. The low dead-volume syringe and needle combination should have a dead volume of no more than 35 microlitres. 

Chemical and physical stability has been shown for 12 hours at 2°C to 30°C with storage of Comirnaty Original paediatric formulations after dilution. ATAGI recommends that after puncture, vials must be kept at 2°C to 30°C and used within 6 hours after initial puncture. Do not re-freeze vaccine. 

ATAGI recommends that, when possible, pre-drawn doses should be used within 1 hour if kept at room temperature, and within 6 hours if kept at 2°C to 8°C, to minimise the risk of infection.

Comirnaty Omicron XBB.1.5 and bivalent formulations

The following guidance applies to:

• Comirnaty Omicron XBB.1.5 5 - <12 years formulation (light blue cap)
• Comirnaty Omicron XBB.1.5 ≥12 years formulation (dark grey cap)
• Comirnaty bivalent Original/Omicron BA.1 (grey cap)
• Comirnaty bivalent Original/Omicron BA.4/5 (grey cap)

The shelf life of frozen vials of the Omicron XBB.1.5 formulations is 24 months at −90°C to −60°C. The shelf life of frozen vials of the bivalent formulations is 18 months at −90°C to −60°C.

Frozen vials should be thawed at 2°C to 8°C. A 10-vial pack may take 6 hours to thaw. Frozen vials can also be thawed at room temperature (up to 30°C) for 30 minutes for immediate use. If the vaccine is received at 2°C to 8°C it should be stored at 2°C to 8°C.

Once thawed, the vaccine should not be re-frozen. See the product information for more details about thawing vials.

After thawing, the shelf life is up to 10 weeks at 2°C to 8°C.

Vaccine may be stored at temperatures between 8°C to 30°C for up to 24 hours.

Both Comirnaty bivalent formulations and Comirnaty Omicron XBB.1.5 ≥12 years formulation (dark grey cap) are presented in a multidose vial with a grey cap, containing 6 doses of 0.3 mL of vaccine.

Comirnaty Omicron XBB.1.5 5 - <12 years formulation (light blue cap) is presented in a single dose vial with a light blue cap, containing 1 dose of 0.3 mL of vaccine.

Do not dilute. Do not shake the vial.

Note that both Comirnaty bivalent formulations have a grey cap and Comirnaty Omicron XBB.1.5 ≥12 years formulation has a dark grey cap. These vaccines are approved for use in different age groups. To minimise the risk of administration errors, providers should preferably prepare and store doses of these vaccines separately. Doses withdrawn in advance of administration should be clearly labelled.

Chemical and physical stability has been shown for 12 hours at 8°C to 30°C with storage of Comirnaty bivalent formulations after initial puncture, and for 12 hours at 2°C to 30°C with storage of Comirnaty Omicron XBB.1.5 formulations after initial puncture. However, because these vaccines contain no antimicrobial preservatives, ATAGI recommends that after puncture, vials must be kept at 2°C to 30°C and used within 6 hours after initial puncture. Do not re-freeze vaccine.

ATAGI recommends that, when possible, pre-drawn doses should be used within 1 hour if kept at room temperature, and within 6 hours if kept at 2°C to 8°C, to minimise the risk of infection.

During storage, minimise exposure to room light. Avoid exposure to direct sunlight and ultraviolet light.

Spikevax bivalent formulations

Spikevax bivalent Original/Omicron BA.4/5 is presented in a pre-filled syringe. A carton contains 5 clear blister packs containing 2 pre-filled syringes in each blister (total 10).

The shelf life of frozen vials is 9 months at –50°C to –15°C. Store frozen in the original carton to protect from light. Do not store below –50°C.

Pre-filled syringes of Omicron XBB.1.5 vaccine should be thawed in the refrigerator at 2°C to 8°C for 2 hours, then left to stand at room temperature (15°C to 25°C) for 15 minutes before administering. Alternatively, each pre-filled syringe may be thawed at room temperature (15°C to 25°C) for 1 hour prior to administering.

Syringes of bivalent vaccine should be thawed in the blister packs (each blister containing 2 pre-filled syringes) or in the carton itself, either in the refrigerator or at room temperature.
Frozen cartons can be thawed in a refrigerator (2°C to 8°C) in 155 minutes, or at room temperature (15°C to 25°C) in 140 minutes.
Frozen blister packs can be thawed in a refrigerator (2°C to 8°C) in 55 minutes, or at room temperature (15°C to 25°C) in 45 minutes.

Pre-filled syringes may be stored refrigerated at 2°C to 8°C, protected from light, for a maximum of 30 days. Once thawed, do not re-freeze.

After taking out of the refrigerator, pre-filled syringes may be stored at 8°C to 25°C for up to 24 hours.

Store frozen cartons away from light. Thawed pre-filled syringes can be handled in room light conditions.

Do not shake or dilute. One (1) dose of 0.5 mL can be administered from each pre-filled syringe. Do not use the pre-filled syringe to deliver a partial 0.25 mL volume.

The prefilled syringe is for single use in one patient only. Discard any residue.

Nuvaxovid

Do not dilute.

Unopened multidose vials should be stored at 2°C to 8°C. Store in the outer carton to protect them from light. Unopened vials are stable for up to 12 hours at 25°C, but storage at 25°C is not the recommended storage or shipping condition.

The shelf life of Nuvaxovid is 9 months at 2°C to 8°C.

Do not shake the vial.

Chemical and physical stability has been shown with storage of Nuvaxovid for 12 hours at 2°C to 25°C after initial puncture. However, because this vaccine contains no antimicrobial preservatives, ATAGI recommends that after initial puncture, vials must be kept at 2°C to 25°C and used within 6 hours from the time of initial puncture.

Data on the stability of pre-drawn doses in syringes are not available for the Nuvaxovid COVID-19 vaccine, so storing pre-drawn doses of this vaccine in syringes is not preferred. If pre-drawn doses are used, ATAGI recommends that (where possible) pre-drawn doses in syringes should be used within 1 hour if kept at room temperature, and within 6 hours if kept at 2°C to 8°C. This is to minimise the risk of infection.

Store at +2°C to +8°C. No dilution of vials is required. Do not freeze. Protect from light.

Transporting doses for home visits

When transporting multidose vial COVID-19 vaccines for a home visit, there are 2 options:

Where possible, transport the vial at 2°C to 8°C and not exceeding the total maximum storage period of 6 hours, and draw up the dose at the site of administration.

A pre-drawn dose in a syringe can be transported if it can be appropriately stored (protecting from light and maintaining the cold chain) and can be administered as soon as practicable and not exceeding the total maximum storage period of 1 hour if kept at room temperature, and 6 hours if kept at 2°C to 8°C).
 

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.

Comirnaty

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. 

Spikevax

The product information for Spikevax states that the recommended interval between primary course doses is 4 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 3–5 months. ATAGI recommends a minimum interval between primary course and further doses of at least 6 months in eligible people.

Nuvaxovid

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

Comirnaty bivalent Original/Omicron BA.1

The product information for Comirnaty bivalent Original/Omicron BA.1 states that it is indicated for use as a further dose. ATAGI considers it suitable for use for primary vaccination of individuals aged ≥ 18 years.

Comirnaty bivalent Original/Omicron BA.4/5

The product information for Comirnaty bivalent Original/Omicron BA.4/5 states that it is indicated for use as a further dose. ATAGI considers it suitable for use for primary vaccination of individuals aged ≥ 12 years.

Spikevax bivalent Original/Omicron BA.4/5

The product information for Spikevax bivalent Original/Omicron BA.4/5 states that it is indicated for use as a further dose. ATAGI considers it suitable for use for primary vaccination of individuals aged ≥ 12 years.

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