COVID-19
Information about COVID-19, vaccines and recommendations for vaccination from the Australian Immunisation Handbook.
Recently added
This page was added on 30 November 2021.
Updates made
This page was updated on 02 May 2025. View history of updates
This chapter is currently undergoing consultation and seeking National Health and Medical Research Council (NHMRC) approval.
Vaccination for certain groups of people is funded under emergency measures, not by the National Immunisation Program or states and territories.
Overview
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.
Recommendations
Infants, children and adolescents
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COVID-19 vaccine is not recommended for healthy infants, children or adolescents who do not have medical conditions that increase their risk of severe illness. This is because the risk of severe illness was is extremely low in this cohort over the course of the pandemic, and benefits of vaccination are not considered to outweigh the potential harms.1,2
View recommendation details
Adults
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Adults aged 18–64 years who do not have severe immunocompromise are recommended to receive a single primary dose of COVID-19 vaccine, and can consider a further dose every 12 months based on individual preference and a risk-benefit assessment. The risk of severe illness from COVID-19 is low in previously vaccinated healthy adults.3,4
Adults aged 65–74 years who do not have severe immunocompromise are recommended to receive a single primary dose of COVID-19 vaccine and further doses of COVID-19 vaccine every 12 months, and can consider doses every 6 months based on a risk-benefit assessment. A dose every 6 months is most likely to benefit people with medical risk conditions and/or those living in residential care facilities.5,6
All adults aged ≥75 years, including aged care residents, are recommended to receive a single primary dose of COVID-19 vaccine, and further doses of COVID-19 vaccine every 6 months. The risk of severe illness increases significantly with advancing age.7-9
View recommendation details
People with medical conditions that increase their risk of severe illness
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For people with relevant medical risk conditions, COVID-19 vaccine dose recommendations vary based on age and the presence of severe immunocompromise (which may reduce the immune response to vaccination). See Table. Example conditions associated with increased risk of severe outcomes from COVID-19, Table. COVID-19 vaccine primary and further dose recommendations for people with medical conditions that increase their risk of severe illness and Table. Examples of severely immunocompromising conditions for which additional primary doses of COVID-19 vaccine are recommended or can be considered.
Table. Example conditions associated with increased risk of severe outcomes from COVID-19This table is not exhaustive, and providers should use their judgement to vaccinate people with conditions not listed.
Condition Example medical condition Immunocompromising condition Immunocompromise due to disease or treatment, asplenia or splenic dysfunction, HIV infection, malignancy, solid organ transplant, haematopoietic stem cell transplant, CAR T-cell therapy
*Individuals with severe immunocompromise are recommended additional COVID-19 vaccines doses. See Table. Severely immunocompromising conditions for which additional doses of COVID-19 vaccine are recommended.Cardiac disease Congenital heart disease, congestive heart failure, coronary artery disease Chronic respiratory condition Severe asthma (requiring frequent medical consultations or the use of multiple medications), cystic fibrosis, bronchiectasis, suppurative lung disease, chronic obstructive pulmonary disease, chronic emphysema Chronic neurological condition Hereditary and degenerative CNS disease, seizure disorder, spinal cord injury, neuromuscular disorder, conditions which impair respiratory or airway function Chronic metabolic condition Type 1 or 2 diabetes, amino acid disorder, carbohydrate disorder, cholesterol biosynthesis disorder, fatty acid oxidation defect, lactic acidosis, mitochondrial disorder, organic acid disorder, urea cycle disorder, vitamin/cofactor disorder, porphyria Chronic kidney disease Chronic renal impairment – eGFR <30 mL/min (stage 4 or 5) Haematological disorder Sickle cell disease or other haemoglobinopathy Chronic liver disease Conditions with progressive deterioration of liver function for more than 6 months, including cirrhosis and other advanced liver diseases Chromosomal abnormality Trisomy 21 or other genetic condition that increases the risk of severe disease Obesity Body mass index ≥30 kg per m2 Table. COVID-19 vaccine primary and further dose recommendations for people with medical conditions that increase their risk of severe illness“Recommended”: benefits of vaccination outweigh the risks for the defined population.
“Consider”: shared decision making between an individual and their healthcare provider.
Age group Level of immunocompromise Primary course recommendations Further (booster) dose recommendations Age 6 months to <5 years Medical risk condition without severe immunocompromise Consider 2 doses, at least 8 weeks apart Not recommended Severe immunocompromise Consider 2-3 doses, at least 8 weeks apart Not recommended Age 5 years to <18 years Medical risk condition without severe immunocompromise Consider 1 primary dose Not recommended Severe immunocompromise Consider 1-2 primary doses, at least 8 weeks apart Consider 1 further dose every 12 months Age 18–64 years Medical risk condition without severe immunocompromise Recommended 1 primary dose Consider 1 further dose every 12 months Severe immunocompromise Recommended 2 primary doses and consider a 3rd, at least 8 weeks apart Recommended 1 further dose every 12 months but can be considered every 6 months Age 65–74 years Medical risk condition without severe immunocompromise Recommended 1 primary dose Recommended 1 further dose every 12 months but can be considered every 6 months Severe immunocompromise Recommended 2 primary doses and consider a 3rd, at least 8 weeks apart Recommended 1 further dose every 12 months, but can be considered every 6 months Age ≥75 years Medical risk condition without severe immunocompromise Recommended 1 primary dose Recommended 1 further dose every 6 months Severe immunocompromise Recommended 2 primary doses and consider a 3rd, at least 8 weeks apart Recommended 1 further dose every 6 months Table. Examples of severely immunocompromising conditions (Ref 10-26) for which additional doses of COVID-19 vaccine are recommended or can be consideredThe example conditions and therapies listed are not exhaustive, and providers may include conditions or therapies similar to those below based on clinical judgement.
Condition Example conditions or treatments Haematological malignancies (untreated, during or < 6months after therapy completion) leukaemia, lymphoma, other lymphoproliferative disorder, plasma cell dyscrasia Malignancy, solid organ transplantation, autoimmune, and inflammatory conditions currently treated with: - haematopoietic stem cell transplant or CAR-T therapy within the last 24 months
- solid organ transplant within the last 12 months
- conventional chemotherapy
- conventional immunosuppressive agent at significant doses, e.g.:
- prednisone ≥20mg/day (≥2mg/kg/day for children) for ≥14 days in a month
- methotrexate >25 mg/week
- azathioprine >3 mg/kg/day
- 6-mercaptopurine >1.5mg/kg/day
- mycophenolate
- tacrolimus and other systemic calcineurin inhibitors
- sirolimus and other mTOR inhibitors
- cyclophosphamide
- rituximab or other B-cell, and T-cell, targeted monoclonal antibody
- monotherapy with infliximab or other anti-TNF alpha monoclonal antibody or anakinra, tocilizumab or other anti-interleukin monoclonal antibody are not considered severely immunocompromising for the purposes of COVID-19 vaccine recommendations
HIV infection Infants (<12 months): CD4+ <750 cells/μL
Children (1–5 years): CD4+ <500 cells/μL
Adults and children >5 years: CD4+ <200 cells/μL
Inborn errors of immunity (primary immunodeficiency) Severe antibody (B-cell) deficiencies, severe combined immunodeficiency (SCID/complete DiGeorge) Chronic kidney disease on dialysis
Women who are pregnant or breastfeeding
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Unvaccinated pregnant women are at increased risk of severe disease and adverse perinatal outcomes from COVID-19.27-29 Unvaccinated pregnant women are recommended to receive a primary dose of COVID-19 vaccine, which can be given at any time during pregnancy.
View recommendation details -
Pregnant women who have previously been vaccinated are not routinely recommended to have a further dose of COVID-19 vaccine. However, they can consider a further dose of COVID-19 vaccine based on presence of underlying risk conditions and/or personal preference.
Previously vaccinated pregnant women who have no conditions that increase the risk of severe illness from COVID-19 have a very low risk of severe illness and pregnancy complications from Omicron infection. 28,30,31 However, a dose administered during pregnancy may reduce the risk of COVID-19 infection and hospitalisation in young infants through transplacental passage of antibodies, noting that the risk of severe illness in healthy young infants is extremely low.32-35
Comirnaty JN.1 and Omicron XBB.1.5-based vaccines can be used in pregnancy. Although the latest mRNA COVID-19 vaccines (Comirnaty JN.1 and Omicron XBB.1.5-based vaccines) have not been formally studied in pregnant women, ATAGI considers them suitable and safe for use.
View recommendation details
People with a history of SARS-CoV-2 infection
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There is no recommended minimum interval between a COVID-19 vaccine dose and infection, recognising that is challenging for many individuals to know if they have had a recent infection. In these circumstances it is appropriate to proceed with a further dose as per the recommended schedule.
Vaccination is likely to enhance the protection induced by infection with the combination of the two called “hybrid immunity). While there is no harm in having a COVID-19 vaccine soon after infection, a greater interval between infection and vaccination has been shown to enhance hybrid immunity by further boosting the immune response generated following infection.36
View recommendation details
Serological testing for immunity to SARS-CoV-2
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Antibody testing is not recommended to assess for immunity to SARS-CoV-2 following COVID-19 vaccination, including when considering further doses. There are no serological assays that provide a definitive correlate of immunity to SARS-CoV-2.
View recommendation details
Vaccines, dosage and administration
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.
Paediatric formulations
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Sponsor:Pfizer AustraliaAdministration route:Intramuscular injection
Registered for use in people aged 5 years to <12 years
COVID-19 vaccine containing nucleoside-modified mRNA encoding the spike glycoproteins of SARS-CoV-2 JN.1 strain.
Single dose vial without preservative containing 0.3 mL of concentrated suspension for injection vaccine. Requires no dilution. Each vial contains 1 dose in 0.48mL.
Each 0.3 mL dose contains:
- 10 µg mRNA encoding the SARS-CoV-2 JN.1 spike glycoprotein
- ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate) (ALC-0315)
- 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC-0159)
- Distearoylphosphatidylcholine (DSPC)
- Cholesterol
- Trometamol
- Trometamol hydrochloride
- Sucrose
- Water for injections
For Product Information and Consumer Medicine Information about Comirnaty JN.1 visit the Therapeutic Goods Administration website.
View vaccine details -
Sponsor:Pfizer AustraliaAdministration route:Intramuscular injection
Registered for use in people aged 6 months - <5 years
COVID-19 vaccine containing nucleoside-modified mRNA encoding the spike glycoproteins of SARS-CoV-2 JN.1 strain.
Multi dose vial without preservative containing 0.3 mL of concentrated suspension for injection vaccine. Requires dilution with 0.9% sodium chloride. Each vial contains 3 doses (0.3mL per dose after dilution) in 0.48mL.
Each 0.3 mL dose contains:
- 3 µg mRNA encoding the SARS-CoV-2 JN.1 spike glycoprotein
- ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate) (ALC-0315)
- 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC-0159)
- Distearoylphosphatidylcholine (DSPC)
- Cholesterol
- Trometamol
- Trometamol hydrochloride
- Sucrose
- Water for injections
For Product Information and Consumer Medicine Information about Comirnaty JN.1 visit the Therapeutic Goods Administration website.
View vaccine details -
Sponsor:Pfizer AustraliaAdministration route:Intramuscular injection
Registered for use in people aged 6 months-<5 years
COVID-19 vaccine containing nucleoside-modified mRNA encoding the spike glycoproteins of SARS-CoV-2 Omicron XBB.1.5 strain.
Multi dose vial without preservative containing 0.4 mL of concentrated suspension for injection vaccine. Requires dilution with 2.2mL of 0.9% sodium chloride. Each vial contains 10 doses in 0.2mL.
Each 0.2 mL dose contains:
- 3 µg mRNA encoding the SARS-CoV-2 Omicron XBB.1.5 spike glycoprotein
- ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate) (ALC-0315)
- 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC-0159)
- Distearoylphosphatidylcholine (DSPC)
- Cholesterol
- Trometamol
- Trometamol hydrochloride
- Sucrose
- Water for injections
For Product Information and Consumer Medicine Information about Comirnaty Omicron XBB.1.5 ([Pfizer] 6 months to <5 years formulation [maroon cap]) visit the Therapeutic Goods Administration website.
View vaccine details -
Sponsor:Pfizer AustraliaAdministration route:Intramuscular injection
Registered for use in people aged 5 - <12 years
COVID-19 vaccine containing nucleoside-modified mRNA encoding the spike glycoproteins of SARS-CoV-2 Omicron XBB.1.5 strain.
Single dose vial without preservative. Each vial contains 1 dose in 0.48mL. Does not require dilution.
Each 0.3 mL dose contains:
- 10 µg mRNA encoding the SARS-CoV-2 Omicron XBB.1.5 spike glycoprotein
- ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate) (ALC-0315)
- 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC-0159)
- Distearoylphosphatidylcholine (DSPC)
- Cholesterol
- Trometamol
- Trometamol hydrochloride
- Sucrose
- Water for injections
For Product Information and Consumer Medicine Information about Comirnaty Omicron XBB.1.5 5 - <12 years (light blue cap) formulation visit the Therapeutic Goods Administration website.
View vaccine details
Adolescent and adult formulations
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Sponsor:Pfizer AustraliaAdministration route:Intramuscular injection
Registered for use in people aged 12 years and above.
COVID-19 vaccine containing nucleoside-modified mRNA encoding the spike glycoproteins of SARS-CoV-2 JN.1 strain.
Multi-dose vial
Multi dose vial without preservative. Each vial contains 6 doses in 2.25mL. Does not require dilution.
Pre-filled syringe
Pre-filled syringe without preservative containing 0.3 mL of concentrated suspension for injection vaccine. Requires no dilution. 1 dose per syringe is available.
Each 0.3 mL dose contains:
- 30 µg mRNA encoding the SARS-CoV-2 JN.1 spike glycoprotein
- ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate) (ALC-0315)
- 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC-0159)
- Distearoylphosphatidylcholine (DSPC)
- Cholesterol
- Trometamol
- Trometamol hydrochloride
- Sucrose
- Water for injections
For Product Information and Consumer Medicine Information about Comirnaty JN.1 visit the Therapeutic Goods Administration website.
View vaccine details -
Sponsor:Pfizer AustraliaAdministration route:Intramuscular injection
Registered for use in people aged >12 years
COVID-19 vaccine containing nucleoside-modified mRNA encoding the spike glycoproteins of SARS-CoV-2 Omicron XBB.1.5 strain.
Multidose vial without preservative. Each vial contains 6 doses in 2.25mL. Does not require dilution.
Each 0.3 mL dose contains:
- 30 µg mRNA encoding the SARS-CoV-2 Omicron XBB.1.5 spike glycoprotein
- ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate) (ALC-0315)
- 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide (ALC-0159)
- Distearoylphosphatidylcholine (DSPC)
- Cholesterol
- Trometamol
- Trometamol hydrochloride
- Sucrose
- Water for injections
For Product Information and Consumer Medicine Information about Comirnaty Omicron XBB.1.5 >12 years (dark grey cap) formulation visit the Therapeutic Goods Administration website.
View vaccine details
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 and precautions
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
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.
Nature of the disease
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.
Clinical features
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
Epidemiology
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
Vaccine information
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 two81,82 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 data42,84 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.
Transporting, storing and handling vaccines
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
Public health management
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.
Variations from product information
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.
References
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Page history
Addition of tables in recommendations section to improve clarity of guidance, updating of immunocompromising and medical conditions list to align with other chapters, removal of information for outdated products.
Updates throughout the chapter to remove outdated formulations (Comirnaty Original [Pfizer] 6 months to ≤5 years formulation, Comirnaty bivalent Original/Omicron BA.4/5 [Pfizer] ≥12 years formulation and Spikevax Omicron XBB.1.5 [Moderna] pre-filled syringe formulation) and added information about updated strain vaccine formulation that is Comirnaty JN.1.
Minor factual updates in relation to individual product (Comirnaty JN.1 formulation) shelf life and registration for use as a primary and further dose vaccine have been made to align with updated production information. Minor updates made to reflect epidemiology of current SARS-CoV-2 circulating variants and effectiveness of Comirnaty JN.1 formulation.
Updates throughout the chapter to remove references to Comirnaty Original 5 < 12 years formulation which is no longer available; and to add information on Comirnaty XBB.1.5 6 months to < 5 years formulation. Minor factual updates in relation to individual product shelf life and registration for use as a booster vaccine have been made to align with updated production information. Minor updates made to reflect current SARS-CoV-2 circulating variants.
Updates throughout the chapter including:
- new recommendations for further doses of COVID-19 vaccine every 6 months for adults aged ≥75 years, every 12 months and consider every 6 months for adults aged 65–74 years, and consider every 12 months for adults aged 18–64 years; people aged ≥6 months with severe immunocompromise are recommended further doses every 12 months and can consider a dose every 6 months
- new recommendations for 1 primary dose of COVID-19 vaccine for adults aged ≥18 years; 2 primary doses with consideration of a 3rd for people aged >6 months with severe immunocompromise; a single primary dose can be considered for children aged 5 to <18 years with other medical conditions that may increase the risk of severe COVID-19
- a table of severely immunocompromising conditions and treatments
- a simplified table of other conditions for which COVID-19 vaccines can be considered
Updates throughout the chapter to reflect that Omicron XBB.1.5 vaccines are now preferred for use in a primary course and as further doses. Other vaccine types are acceptable, but Omicron XBB.1.5-containing vaccines are preferred. Other changes reflect the availability of the new vaccine formulations and unavailability of older vaccines (such as the Spikevax original 6 months - <5 years formulation).
Major update to provide an enhanced COVID-19 disease chapter that consolidates the available COVID-19 clinical guidance material.
Addition of tables in recommendations section to improve clarity of guidance, updating of immunocompromising and medical conditions list to align with other chapters, removal of information for outdated products.
Updates throughout the chapter to remove outdated formulations (Comirnaty Original [Pfizer] 6 months to ≤5 years formulation, Comirnaty bivalent Original/Omicron BA.4/5 [Pfizer] ≥12 years formulation and Spikevax Omicron XBB.1.5 [Moderna] pre-filled syringe formulation) and added information about updated strain vaccine formulation that is Comirnaty JN.1.
Minor factual updates in relation to individual product (Comirnaty JN.1 formulation) shelf life and registration for use as a primary and further dose vaccine have been made to align with updated production information. Minor updates made to reflect epidemiology of current SARS-CoV-2 circulating variants and effectiveness of Comirnaty JN.1 formulation.
Updates throughout the chapter to remove references to Comirnaty Original 5 < 12 years formulation which is no longer available; and to add information on Comirnaty XBB.1.5 6 months to < 5 years formulation. Minor factual updates in relation to individual product shelf life and registration for use as a booster vaccine have been made to align with updated production information. Minor updates made to reflect current SARS-CoV-2 circulating variants.
Updates throughout the chapter including:
- new recommendations for further doses of COVID-19 vaccine every 6 months for adults aged ≥75 years, every 12 months and consider every 6 months for adults aged 65–74 years, and consider every 12 months for adults aged 18–64 years; people aged ≥6 months with severe immunocompromise are recommended further doses every 12 months and can consider a dose every 6 months
- new recommendations for 1 primary dose of COVID-19 vaccine for adults aged ≥18 years; 2 primary doses with consideration of a 3rd for people aged >6 months with severe immunocompromise; a single primary dose can be considered for children aged 5 to <18 years with other medical conditions that may increase the risk of severe COVID-19
- a table of severely immunocompromising conditions and treatments
- a simplified table of other conditions for which COVID-19 vaccines can be considered
Updates throughout the chapter to reflect that Omicron XBB.1.5 vaccines are now preferred for use in a primary course and as further doses. Other vaccine types are acceptable, but Omicron XBB.1.5-containing vaccines are preferred. Other changes reflect the availability of the new vaccine formulations and unavailability of older vaccines (such as the Spikevax original 6 months - <5 years formulation).
Major update to provide an enhanced COVID-19 disease chapter that consolidates the available COVID-19 clinical guidance material.