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Clinical recommendations for COVID-19 vaccines 
The Australian Technical Advisory Group on Immunisation (ATAGI) has made recommendations on 
the use of COVID-19 vaccines in Australia. 
On this page 

Primary course: vaccine preference recommendations

Booster dose recommendations

Considerations for special populations

Recommended and variations on vaccination schedule

Minimum valid dose schedules

Mixed (heterologous) schedules

Further reading
COVID-19 vaccination is recommended for all people aged 5 years or older to protect against 
COVID-19. For most people, a primary vaccination course consists of 2 doses. 
A third primary dose is recommended for people aged 5 years or older with 
of  severe 
immunocompromise. See considerations for special populations: people who are 
A single booster dose is recommended for people aged 16 years or older
Feedom  , 3 months after the primary 
course. An additional booster dose is recommended for people at risk of severe COVID-19, 4 months 
after the first booster. See booster dose recommendations. 
In Australia, vaccination is strongly recommended for the following groups: 

people with occupational risk of exposure to SARS-CoV-2, such as frontline healthcare
workers, quarantine and border workers, aged care and disability care staff, and critical and
high-risk workers

residents of aged care and disability care facilities

older adults

Aboriginal and Torres Strait Islander people

people with underlying m
was  edical conditions that increase their risk of severe COVID-19

pregnant women
Primary course: vaccine preference recommendations 
Adults aged under 60 years 
Pfizer, Moderna, or Novavax COVID-19 vaccines are preferred over AstraZeneca for people aged 
under 60 years. This is based on the higher risk and observed severity of thrombosis with 
thrombocytopenia syndrome (TTS) after receiving AstraZeneca vaccine in people aged under 60 
years compared with people aged 60 years or older. People aged 60 years or older are also at higher 
risk of severe illness from COVID-19, meaning the benefits of vaccination outweigh the very small 
risk of TTS. 
AstraZeneca COVID-19 vaccine can be used in adults aged under 60 years if the person has made an 
informed decision based on an understanding of the risks and benefits.1 
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For more information on third primary doses for severely immunocompromised individuals 
see: Considerations for special populations – people who are immunocompromised. 
Adults aged 60 years or older 
There is no brand preference for people aged 60 years and older. 
People aged 60 years and older receive greater benefit from vaccination than young people. This is 
because the risk of severe disease from COVID-19 increases with age. The benefit of vaccination with 
AstraZeneca in preventing COVID-19 outweighs the risk of TTS in people aged 60 years and older. 
For information on third primary doses for severely immunocompromised individuals 
see: Considerations for special populations – people who are immunocompromised. 
Pregnant women 
mRNA COVID-19 vaccines (Pfizer or Moderna) are the recommended vaccines in pregnancy. There 
are substantial data on their safe use in pregnancy. 
Novavax COVID-19 vaccine can also be used in pregnancy. There is no immunogenicity or safety 
data but there are no theoretical safety concerns. 
AstraZeneca is not preferred in pregnancy. Pregnant women who have already received a first dose of 
AstraZeneca can receive either an mRNA COVID-19 vaccine, AstraZene
Feedom  ca, or Novavax for their 
second dose. 
Booster dose recommendations 
A single COVID-19 vaccine booster dose is recommended for people aged 16 years and older who 
completed their primary course 3 or more months ago. 
An additional booster dose (also known as a winter dose) is recommended for people in the following 
groups, from 4 months after the first booster dose: 
•  people 65 years or older 
•  residents of an aged care or disability care facility 
•  people who are severely immunocompromised 
•  Aboriginal and Torres Strait Islander peoples aged 50 years and older. 
For people aged 16 to 17 y
document  ears, Pfizer COVID-19 vaccine is the only vaccine registered for use as a 
For people aged 18 years and older, Pfizer or Moderna COVID-19 vaccines are the preferred vaccines 
for a booster dose, regardless of which vaccine was used for the primary course. 
Although not preferred, AstraZeneca can be used as a booster dose if there are no alternative, for 
•  people who are contraindicated to or had a serious adverse event from mRNA vaccines, e.g. a 
history of anaphylaxis or myocarditis attributed to  an mRNA vaccine 
•  people who refuse to have a preferred vaccine. 
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Novavax COVID-19 vaccine is not registered for use as a booster dose, however it can be used as a 
booster dose in an individual aged 18 or older if no other COVID-19 vaccine brand is suitable for that 
There is a growing body of evidence supporting the safety and effectiveness of Pfizer and Moderna as 
booster vaccines. Data on the use of AstraZeneca as a booster dose are more limited (see Vaccine 
information – clinical guidance). There is very limited data on the use of Novavax as a booster dose. 
The recommended interval between completing the primary COVID-19 vaccine course (the second 
dose for most vaccine brands) and the first booster dose is 3 months. 
The recommended interval between the first booster dose and a second booster dose (for those who 
are recommended to receive a second booster dose) is 4 months. 
There is no upper time limit for the administration of a booster dose. However, vaccine effectiveness 
wanes over time, and timely receipt of boosters is encouraged for people who will particularly benefit, 
•  people at greater risk of severe COVID-19 – people aged 50 years and older, people with 
underlying medical conditions, residents of aged care and disability
of   facilities, and Aboriginal 
and Torres Strait Islander adults. 
•  people at increased occupational risk of COVID-19 
•  people living in jurisdictions with active community transmission. 
The evidence underpinning booster dose recommendations will continue to be reviewed and this 
clinical guidance may be refined. 
The effectiveness of currently available COVID-19 vaccines against the Omicron variant is not yet 
known. Laboratory studies suggest that a booster dose
under   of an mRNA COVID-19 may be required to 
induce adequate neutralising antibody titres against this variant. For more information see: ATAGI 
Statement on the Omicron variant and the timing of COVID-19 booster vaccination. 
In severely immunocompromised people aged 16 years or older who have been recommended to 
receive a third dose as part of their primary C
released  OVID-19 vaccine course, booster doses (that is, a fourth 
dose) are recommended 3 months after the most recent dose in the primary course. People in this 
group are also recommended to ha
was  ve an additional booster (winter dose) from 4 months after the first 
booster dose. 
Booster doses are not yet recommended for people under 16 years of age. This advice will be updated 
as more information is available. 
For more information on booster doses, see: 
•  ATAGI recommendations on the use of a booster dose of COVID-19 vaccine 
•  ATAGI recommendations on the use of Moderna as a booster dose 
•  ATAGI recommendations for use of Pfizer COVID-19 vaccine as a booster dose in 
adolescents aged 16-17 years 
•  ATAGI statement on the Omicron variant and the timing of COVID-19 booster vaccination. 
•  ATAGI recommendations on a winter booster dose of COVID-19 vaccine 
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Considerations for special populations 
People who are immunocompromised 

COVID-19 vaccine is recommended for people who are immunocompromised because of their 
increased risk of severe illness with COVID-19.2 
A third primary dose of COVID-19 vaccine is recommended for people aged 5 years or older with 
severe immunocompromise from 2 months after the second vaccine dose. 
This dose is intended to address the risk of lowered or non-response to the standard 2 dose schedul
Act  e. 
An mRNA COVID-19 vaccine (Pfizer or Moderna) is recommended for the third dose. This is 
because most studies of third doses of COVID-19 vaccine in immunocompromised people have used 
mRNA vaccines. 
The Novavax COVID-19 vaccine can be used for the third dose for people who have received
Novavax for their first 2 doses, or if there are contraindications to mRNA C
of  OVID-19 vaccines. There 
is very limited evidence of the efficacy of Novavax in immunocompromised people. 
The AstraZeneca COVID-19 vaccine is not preferred but can be used for the third dose if there are 
contraindications to mRNA COVID-19 vaccines. 
Severely immunocompromised people aged 16 years or ol
the der who have received a third primary dose 
are recommended to receive: 
•  a booster dose (a fourth dose), 3 months after
under   the primary course, in line with the general 
•  an additional booster dose (a fifth dose), 4 months after the first booster. 
More information, including definitions of severe immunocompromise, is available in ATAGI 
recommendations for the use of a 3rd primar
released  y dose of COVID-19 vaccine in individuals who are 
severely immunocompromised. 
There are many causes and varying degrees of immunocompromise. The risk of COVID-19 will vary 
according to: 
•  the number and type of underlying conditions 

medical management 
•  other factors. 
Immunogenicity studies in immunocompromised populations are limited and immunocompromised 
populations are clinically diverse. It is difficult to predict anticipated protection against asymptomatic 
infection, symptomatic infection, hospitalisation and severe disease. 
This is because there is no clear correlate of protection from immunogenicity data. 
Vaccinated immunocompromised people should be advised to continue taking other protective 
measures against SARS-CoV-2. 
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For more details, see the COVID-19 vaccination decision guide for people with 
immunocompromise and Provider guide to COVID-19 vaccination in people with 
Effectiveness studies3,4 in immunocompromised people confirm that it is essential to receive 2 doses 
of a COVID-19 vaccine, as protection may be suboptimal after a single dose. Estimates of vaccine 
effectiveness range from 4% to 43%3-5 in partially vaccinated immunocompromised people. These 
studies were conducted before the widespread dominance of the Delta variant and may reflect 
effectiveness against older strains. 
For more details on vaccine effectiveness in people who are immunocompromised, see COVID-19 1982
vaccine information. 
Children and adolescents 
COVID-19 vaccination is recommended for all children and adolescents aged 5 years or older. 
Children aged 5 to 11 years 
Two vaccines are available for young children. 
•  The paediatric formulation of Pfizer COVID-19 vaccine is registered for use in children 
aged 5 to 11 years. The paediatric formulation differs from the adolescent/adult formulation 
in its concentration and recommended dosing (see Vaccines, dos
Feedom  age and administration – 
clinical guidance). Children aged 5 to 11 years should not receive the adolescent/adult 
formulation of the Pfizer vaccine. The Pfizer vaccine is the only COVID-19 vaccine 
registered for children who are 5 years old. 
•  The Moderna COVID-19 vaccine is registered for use in children aged 6 to 11 years. There is 
no separate paediatric formulation of the Mode
under  rna vaccine – children aged 6 to 11 years 
receive half the adult dose (50µg in 0.25 mL). ATAGI recommends that providers are vigilant 
about the potential for dosing errors, including overdosing, with the Moderna vaccine in 
If the Moderna vaccine is inadvertently given to a child who is 5 years of age, the paediatric 
formulation of the Pfizer vaccine should be given as the second dose. 
Adverse events after the Moderna vaccine in young children are reported to be usually mild to 
moderate and transient, but may be more common than adverse events after the paediatric Pfizer 
vaccine. For more information see Adverse events – clinical guidance. 
AstraZeneca and Novavax vaccines are not registered for use in children aged 5 to 11 years. 
This  nts aged 12 to 17 years 
Pfizer and Moderna COVID-19 vaccines are registered for use in people aged 12 years or older. 
The AstraZeneca and Novavax COVID-19 vaccines are only registered in people aged 18 years and 
older. If AstraZeneca or Novavax are inadvertently given as a first dose to a person aged under 18 
years, Pfizer of Moderna should be used for the second dose. 
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Booster doses are not recommended in children aged 5 to 15 years 
Booster doses are not recommended for people aged under 16 years. 
Severe COVID-19 in children is uncommon and the primary course of COVID-19 vaccines generates 
a strong immune response. The benefit from additional doses of vaccine is likely to be small and 
current evidence does not suggest that booster doses are needed at this time. 
Benefits of vaccination for children and adolescents 
Children aged 5 to 11 years in the following groups are most likely to benefit from COVID-19 
vaccination because of their increased risk of severe outcomes and/or exposure: 
•  children with medical risk factors for severe illness 
•  Aboriginal and Torres Strait Islander children 
•  children living in crowded conditions or outbreak areas. 
Most children with SARS-CoV-2 infection are asymptomatic or have a mild illness. Adolesc
Information  ents 
appear to have similar infection rates to adults. But the frequency of severe 
of illness from COVID-19 is 
lower in adolescents than in adults, with approximately 4% to 7% of adolescents experiencing severe 
Adolescents and children are accounting for increasing proportions of COVID-19 cases, in the context 
of vaccinated older age groups. Overall hospitalisation rates for COVID-19 in the adolescent age 
group are higher than for other viral respiratory diseases such as influenza.8 
Vaccinating children and adolescents is anticipated to prevent: 
•  SARS-CoV-2 infections, hospitalisations and deaths due to COVID-19 
•  paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 
(PIMS-TS). PIMS-TS is a rare but serious condition associated with COVID-19 in children, 
which can present with features similar to those of Kawasaki disease or toxic shock 
•  post-COVID-19 condition (‘long COVID’). 
For more information see ATAGI recommendations on the use of the paediatric Pfizer COVID-19 
vaccine in children aged 5 to 11 years in Australia, ATAGI recommendations on the use of Spikevax 
(Moderna) COVID-19 vaccine in children aged 6 to 11 years and ATAGI statement regarding 
vaccination of adolescents aged 12-15 years. 
Pregnancy, breastfeeding or planning pregnancy 
mRNA vaccines (Pfizer or Moderna) are the recommended COVID-19 vaccines for pregnant women. 
This is based on the growing body of evidence supporting the safety of mRNA vaccines in pregnancy, 
whereas there are still very limited data on the safety of the other COVID-19 vaccines (AstraZeneca 
and Novavax) in pregnancy. However, people who cannot access an mRNA vaccine can consider 
vaccination with AstraZeneca or Novavax if the benefits to the individual outweigh the potential risks. 
Women aged 16 years or older who are pregnant and had their primary course at least 3 months ago 
are recommended to receive a booster dose. Pfizer or Moderna are the preferred brands for the booster 
dose, regardless of the brand that was given for the primary course. 
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For more details, see Shared decision making guide for women who are pregnant, breastfeeding or 
planning pregnancy. 
For details on:   
•  vaccine effectiveness in pregnancy, see COVID-19 vaccine product information 
•  risk of COVID-19 in pregnancy, see Clinical features of COVID-19 disease 
•  adverse events and safety in pregnancy, see COVID-19 vaccine adverse events. 
People with a past SARS-CoV-2 infection 
All people are recommended to defer COVID-19 vaccination for 3 months after a confirmed SARS-
CoV-2 infection, to optimise protection for that person. The next scheduled dose should then be gi
Act  ven 
as soon as possible. All recommended doses should still be received, and no doses should be omitted 
from the schedule. 
The risk of reinfection with the Omicron variant is very low within the first 3 months following a 
confirmed infection10. The Delta variant is no longer circulating in Australia. This advice may change 
if future variants of SARS-CoV-2 emerge. 
Vaccination is likely to enhance the protection induced by infection. The interval between infection 
and vaccination enhances the protection from vaccination by further boosting the immune response, 
including immune memory response, generated following infection11.   
An individual may be vaccinated earlier than the recommended 3-month interval in exceptional 
circumstances, such as prior to starting an immunosuppressa
the  nt, prior to overseas travel or if someone 
cannot reschedule vaccination easily (e.g. outreach vaccination program). 
Infection can be confirmed by either PCR or rapid ant
under igen test. Results of rapid antigen tests should 
be reported to jurisdiction reporting systems (where applicable). 
For people who have been infected and are required to receive COVID-19 vaccination, a temporary 
medical exemption may be applicable. People should speak with their healthcare provider about what 
is best for them. Providers are advised to onl
released y provide temporary exemptions for a period of up to 4 
months post-infection. This is due to the increased risk of reinfection after this time. 
People who were previously vaccinated within 3 months of a confirmed SARS-CoV-2 infection do 
not need to repeat any doses.   
People who have been infected with SARS-CoV-2 can receive other (non-COVID) vaccines without 
any minimum interval. A
document  s with any vaccine, vaccination should be deferred in people who are acutely 
unwell (e.g., acute febrile or systemic illness). 
People treated with an anti-SARS-CoV-2 monoclonal antibody 
Anti-SARS-CoV-2 monoclonal antibodies can be used for treatment in the setting of SARS-CoV-2 
infection, or as pre or post -exposure prophylaxis. When given following infection, ATAGI does not 
recommend a specific minimum time to defer vaccination due to monoclonal antibody therapy. 
However, people are still recommended to follow guidance to defer vaccination for 3 months 
following infection (see People with a past SARS-CoV-2 infection). 
As with all vaccines, COVID-19 vaccination should be deferred in people who are acutely unwell.   
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Timing of administration of other vaccines 
COVID-19 vaccines can be co-administered (that is, given on the same day) with an influenza 
vaccine. Studies demonstrate the safety and immunoge.nicity of co-administration of COVID-19 and 
influenza vaccines.   
COVID-19 vaccines can also be co-administered with other vaccines if required.   
This includes routine childhood and adolescent vaccines. The benefits of ensuring timely vaccination 
and maintaining high vaccine uptake outweigh any potential risks associated with immunogenicity, 
local adverse reactions or fever. 
There is limited evidence on the safety and effectiveness of co-administering COVID-19 vaccines at 
the same time as other vaccines. Providers need to balance the opportunistic need for co-
administration with the benefits of giving the vaccines on separate visits. There is the potential for an 
increase in mild to moderate adverse events when more than one vaccine is given at the same time. 
Co-administration or near administration (e.g. within days) with another vaccine may also make it 
challenging to attribute potential adverse events.12,13 Providers should ensure that parents/guardians of 
young children receiving COVID-19 vaccines are aware of the increased potential for local 
Information reactions. 
Co-administration of antipyretics or analgesics 
Using paracetamol or ibuprofen before receiving a COVID-19 vaccine is not recommended. 
Pain relievers such as antipyretics and analgesics can be taken after vaccination if needed to manage 
vaccine-related side effects such as fever and myalgia. 
Recommended and variations on vaccination schedule 
COVID-19 vaccine dosing interval for children aged 5 to 11 years 
ATAGI recommends a dosing schedule for paediatric Pfizer vaccine or the paediatric dose of 
Moderna vaccine of 2 doses, 8 weeks apart. The 
manufacturer’s recommended dosing schedule for 
paediatric Pfizer vaccine is 2 doses, 3 weeks apart; and for Moderna vaccine, 2 doses, 4 weeks apart. 
The recommended longer dosing interval will allow more time to observe international data on 
potentially rare adverse events in this age group. It may also improve immunogenicity. In adult 
populations, extending the interval to 8 weeks or longer has resulted in higher antibody levels, 
improved vaccine effectiveness and potentially longer duration of protection compared with the 
standard interval.14-16 Exte
document  nded dosing intervals have not yet been directly studied in children. This 
recommendation is consistent with other national immunisation technical advisory groups, such as the 
National Advisory Committee on Immunization in Canada.17 
For children who turn 12 between their first and second doses, the recommended dosing interval is 3-
8 weeks for Pfizer vaccine and 4-8 weeks for Moderna vaccine. When determining the most 
appropriate dose interval providers should consider: 
•  the potential for improved immunogenicity and fewer rare side effects with a longer dose 
•  local epidemiology 
•  individual circumstances including underlying risk of COVID-19 to the child and parental 
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Also see: Mixed (heterologous) schedules. 
Shorter dose intervals 
The dose interval for paediatric Pfizer vaccine can be shortened to a minimum of 3 weeks. The 
interval can be shortened in special circumstances to a minimum of 3 weeks, for higher risk groups 
(such as those with medical risk factors for severe illness), or before international travel. 
The dose interval for paediatric doses of Moderna vaccine can be shortened in the same special 
circumstances to a minimum of 4 weeks. 
The benefits of earlier protection should be weighed against the benefits of the longer dose interval
Act  , 
such as a slightly lower risk of adverse events and a longer duration of protection. 
Longer dose intervals 
If the second dose of paediatric Pfizer vaccine or the second paediatric dose of Moderna vaccine is 
administered later than the recommended interval, no further doses are recommended. 
Pfizer and Moderna COVID-19 vaccine dosing interval for adolescents and 
ATAGI recommends a primary dosing schedule of the adolescents/adults Pfizer COVID-19 vaccine 
or Moderna COVID-19 vaccine of 2 doses, 8 weeks apart. T
the  he manufacturer’s dosing schedule for 
Pfizer is 2 doses, at least 21 days (3 weeks) apart; and for Moderna vaccine, 2 doses, 4 weeks apart. 
The extended interval of 8 weeks may improve vaccin
under  e effectiveness. The longer interval may also 
reduce the risk of myocarditis and pericarditis, particularly for those most at risk of these side effects 
(males, aged 12 to 39 years). 
For more information see: ATAGI guidance on myocarditis and pericarditis after mRNA COVID-19 
Although Pfizer and Moderna m
was  ay provide partial protection against COVID-19 as soon as 12 days 
after the first dose, this protection is likely to be short lived. A 2-dose course is recommended for 
optimal protection. 
Shorter dose intervals 
The dosing interval can be shortened to a minimum of 3 weeks for Pfizer or 4 weeks for Moderna. 
This short
This er interval can be used in specific circumstances for higher risk groups (such as older people 
or those with medical risk factors for severe illness), or before international travel. 
Providers should consider the potential risk of myocarditis and pericarditis when selecting a COVID-
19 vaccine brand and dose interval, taking into account the person’s age, preferences and any 
precautions to specific vaccine brands. 
Shortening of the recommended dose interval below the manufacturer’s dosing schedule may result in 
a suboptimal immune response. 
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If the dose interval is at least 14 days, then both doses are considered valid and no doses need to be 
repeated. This is because there are no data on administration of more than 2 vaccine doses given in a 
short time, and the person is still likely to have good protection. 
For more information, see use of an additional COVID-19 vaccine dose as a replacement dose if the 
second dose was given less than 14 days after the first dose. 
Longer dose intervals 
If the second dose of Pfizer or Moderna is administered later than the recommended interval, no 
further doses are recommended. 
AstraZeneca COVID-19 vaccine dosing interval 
The recommended interval between 2 doses of the AstraZeneca COVID-19 vaccine is 12 weeks. 
The minimum interval between doses is 4 weeks. 
The duration of protection after a single dose of AstraZeneca has not yet been established. A
Information  second 
dose is recommended for optimal protection. 
Shorter dose intervals 
Shortening of the recommended dose interval may result in a suboptimal
Feedom   immune response. 
It is acceptable to shorten the interval between doses from 12 w
eeks to no less than 4 weeks. This may 
be appropriate in certain circumstances – for example, imminent travel or anticipated risk of SARS-
CoV-2 exposure. 
In an outbreak setting, ATAGI recommends an interval of 4 to 8 weeks between doses. 
If the dose interval is at least 14 days, then both doses are considered valid and no doses need to be 
repeated. This is because there are no data on administration of more than 2 vaccine doses given in a 
short time, and the person is still likely to have good protection. 
In clinical trials, the timing of administration of AstraZeneca ranged from around 4 weeks to up to 26 
weeks. In a post-hoc analysis, vaccine efficacy after the second dose of AstraZeneca progressively 
increased with a longer interval between doses. Efficacy was greatest when the interval was 12 weeks 
or more. Short-term efficacy was about 73% (95% CI: 48.8–85.8) from 3 weeks after the first dose to 
12 weeks after the first dose.18 
Also see vaccine information – clinical guidance for more details. 
For more information, see Use of an additional COVID-19 vaccine dose as a replacement dose if the 
second dose was given less than 14 days after the first dose. 
Longer dose intervals 
If the second dose of AstraZeneca COVID-19 vaccine is administered later than the recommended 
interval, no further doses are required. 
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Novavax COVID-19 vaccine dosing interval 
The recommended interval between 2 doses of the Novavax COVID-19 vaccine is a minimum of 3 
The interval can be extended to 8 weeks in certain circumstances, including to reduce the potential 
risk of rare side effects such as myocarditis and pericarditis. 
The duration of protection after a single dose of Novavax has not yet been established. A second dose 
is recommended for optimal protection. 
Shorter dose intervals 
Shortening of the recommended dose interval may result in a suboptimal immune response. 
If the dose interval is at least 14 days, then both doses are considered valid and no doses need to be 
repeated. This is because there are no data on administration of more than 2 vaccine doses given in a 
short time, and the person is still likely to have good protection. 
For more information, see Use of an additional COVID-19 vaccine dose as a
of   replacement dose if the 
second dose was given less than 14 days after the first dose. 
Longer dose intervals 
If the second dose of Novavax is administered later than the recommended interval, no further doses 
are recommended. 
Minimum valid dose schedules
ATAGI advises that the absolute minimum interval between the first and second dose of any COVID-
19 vaccine is 14 days.  Dose intervals of at least 14 days are considered acceptable and valid, and the 
person will be considered fully vaccinated in the Australian Immunisation Register (AIR). 
Use of an additional COVID-19 vaccine dose as a replacement dose if the 
second dose was given less than 14 days after the first dose 
A second dose of a COVID-19 vaccine administered <14 days after the first dose is considered an 
invalid dose. An additional COVID-19 vaccine dose should be administered as a replacement dose. 
The aim of this replacement dose is to attain a level of immune response that is comparable to that 
expected after completing a 2-dose primary course of a COVID-19 vaccine according to the 
This  ed dosage and schedule. 
The same COVID-19 vaccine brand should be used for the replacement dose to complete the primary 
vaccination course, unless there are special circumstances indicating the use of an alternative vaccine. 
Refer to the ATAGI clinical advice on use of a different COVID-19 vaccine as the second dose in 
special circumstances. 
The interval between the invalid second dose and the replacement dose is flexible but is recommended 
at 4 to 12 weeks after the invalid second dose. Timing of the replacement dose should be informed by 
an individual risk-benefit assessment that considers: 
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•  risk of exposure to SARS-CoV-2 – for example, workers in health care, aged care, disability 
care, border and quarantine facilities may warrant vaccination with a replacement dose 
•  local disease epidemiology 
•  mandatory vaccination requirements for work (such as aged care or healthcare workers) 
•  individual medical conditions associated with increased risk of severe COVID-19 (such as 
There are no direct clinical trial data on vaccines used in Australia regarding a second dose being 
administered at <14 days after the first dose. The recommendation for a replacement dose is based on 
first principles. It takes into consideration the small amount of preliminary data in trials where  1982
participants received a third dose of the vaccine (at various intervals), and the potential incremental 
benefits outweighing the potential adverse effects. 
These recommendations do not apply to booster doses. 
Mixed (heterologous) schedules 
ATAGI prefers use of the same COVID-19 vaccine for the 2 doses of the pr
of  imary course.   
An alternative vaccine brand for dose 2 should be used if there are specific medical contraindications 
or precautions, or if the same vaccine brand is not available in Australia.   
It is preferable to use the same brand for both doses of the primary course, but an alternative brand 
can be used for the second dose for other reasons. Examples
the   include if a person is unable to access the 
same brand or does not accept a second dose of the same brand. Emerging data support the safety and 
efficacy of mixed schedules. 
Mixed schedules of Therapeutic Goods Administration (TGA)-approved or TGA-recognised vaccines 
are acceptable. 
The recommended interval between first and second doses of a mixed schedule is 4 to 12 weeks after 
the first dose, regardless of first dose brand. A
released  n interval longer than 12 weeks is acceptable if the 
second dose cannot be administered during this time window. 
Short-term adverse reactions are slightly more likely to occur in people who have a different vaccine 
for dose 2 than if they had the same vaccine for both doses, but the nature and severity of the adverse 
events are similar.19-25 
Emerging data show that
document   mixed schedules stimulate an adequate or comparable immune response 
compared with using the same brand for both doses. These trials have mostly been conducted with 
AstraZeneca COVID-19 vaccine as dose 1 and either Pfizer or Moderna COVID-19 vaccine as dose 
2. One randomised controlled trial with 100 participants used Pfizer as the first dose followed by 
AstraZeneca as the second dose. These studies also showed an acceptable safety profile in the small 
cohorts vaccinated with mixed schedules.19-23,25,27   
Results from studies investigating mixed schedules of only mRNA vaccines (Pfizer and Moderna) in a 
primary course is limited. Preliminary results from a Canadian observational cohort study in people 
aged 65 years and older found no significant differences in antibody responses, 4 weeks after the 
second dose of Pfizer following a first dose of Moderna, compared with those who received the same 
vaccine for both doses. Reactogenicity was not reported in this study.28 
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One study investigated AstraZeneca as the second dose following a first dose of an mRNA vaccine. 
This study showed that the immune response after a first dose of Pfizer followed by AstraZeneca was 
lower than two doses of Pfizer.19 
Currently there are no data showing the efficacy or safety of mixed doses using the Novavax vaccine 
for one of the doses. However, there are no theoretical concerns of mixed doses with Novavax. 
Special circumstances for mixed schedules 
In the following special circumstances, an alternative formulation, brand or vaccine platform may be 
recommended for the second dose (if not contraindicated). 
Children who turn 12 after their first dose of paediatric Pfizer or Moderna 
Children who turn 12 after their first dose of paediatric Pfizer or Moderna vaccine should receive the 
adolescent/adult dose and formulation of the Pfizer or Moderna vaccine to complete their primary 
vaccine course. 
People with serious vaccine-attributable adverse events after dose 1 that 
warrant the use of an alternative vaccine brand for dose 2 
Serious vaccine-attributable adverse events include:  the 
•  anaphylaxis to the first dose of a COVID-19 vaccine (note: anaphylaxis to a previous dose of 
an mRNA COVID-19 vaccine (Pfizer or Moderna) is a contraindication to further doses of 
either vaccine), OR   
•  thrombosis with thrombocytopenia following the first dose of AstraZeneca, OR 
•  any other serious adverse event attributed to a previous dose of a COVID-19 vaccine (and 
without another cause identified) that: 
•  has been reported to State or Territory adverse event reporting programs and/or the TGA, 
•  has been determined to be serious following review by, and/or on the opinion of, an 
experienced immunisation provider/medical specialist taking into account whether repeat 
vaccine doses would be associated with a risk of recurrence of the serious adverse event. 
Assessment of adverse events following immunisation requires detailed information about the event 
and the severity of the condition, as well as a determination of the likelihood of a causal link with 
vaccination. Serious adverse events are generally defined as those which: 
•  require hospitalisation (for example, thrombosis with thrombocytopenia following the first 
This   of AstraZeneca) 
•  are medically significant (for example, immune thrombocytopenia purpura, myocarditis) 
•  are potentially life-threatening (for example, anaphylaxis), and/or 
•  result in persistent or significant disability (for example, Guillain-Barré syndrome). 
These reactions do not typically include expected local or systemic reactions that are known to occur 
within the first few days after vaccination. Attributing a serious adverse event to a previous dose of a 
COVID-19 vaccine may require discussion with the person’s GP, local immunisation service or 
relevant medical specialist. 
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People with a precautionary condition for which the use of an 
alternative COVID-19 vaccines is recommended instead of AstraZeneca 
Precautionary conditions are: 
•  history of cerebral venous sinus thrombosis (CVST) 
•  history of heparin-induced thrombocytopenia (HIT) 
•  history of idiopathic splanchnic (mesenteric, portal, splenic) venous thrombosis 
•  history of anti-phospholipid syndrome (APLS) with thrombosis. 
People given an incomplete course of a COVID-19 vaccine brand that is not 
available in Australia 
People who received a first dose of a COVID-19 vaccine overseas that is not available in Australia 
can be offered an alternative vaccine brand available in Australia to complete their primary 
vaccination course.   
The TGA has information on vaccines that are recognised for the purposes of travel to Australia. 
People who have had a first dose of a vaccine that is not recognised by the TG
of  A (or are unable to 
provide evidence of previous vaccine doses) should restart the primary vaccination course using a 
TGA approved or recognised vaccine. It is recommended that the new primary vaccination course 
commences 4 to 12 weeks after the last vaccine dose. 
Further reading 
1.  Australian Technical Advisory Group on Immunisation (ATAGI). ATAGI statement regarding 
COVID-19 vaccines in the setting of transmission of the Delta variant of concern. Published online on 
2 August 2021 (Accessed 9 September 2021).
2.  Gao Y, Chen Y, Liu M, Shi S, Tian J. Impacts of immunosuppression and immunodeficiency on 
COVID-19: a systematic review and meta-analysis. Journal of Infection 2020;81:e93-e5. 
3.  Whitaker HJ, Tsang RSM, Byford R, et al. Pfizer-BioNTech and Oxford AstraZeneca COVID-19 
vaccine effectiveness and immune response among individuals in clinical risk groups. 2021. (Accessed 
12 August 
was ocuments/135939561/430986542/RCGP+VE+riskgroups+paper.pdf/a6b54cd9
4.  Young-Xu Y, Korves C, Roberts J, et al. Coverage and Effectiveness of mRNA COVID-19 Vaccines 
among Veterans. 2021. (Accessed 12 August 2021). 
5.  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. Gastro
document  enterology 2021. 
6.  Götzinger F, Santiago-García B, Noguera-Julián A, et al. COVID-19 in children and adolescents in 
Europe: a multinational, multicentre cohort study. The Lancet Child & Adolescent Health 2020;4:653-
This 61. 
7.  Molteni E, Sudre CH, Canas LS, et al. Illness duration and symptom profile in symptomatic UK 
school-aged children tested for SARS-CoV-2. The Lancet Child & Adolescent Health 2021. 
8.  Havers FP, Whitaker M, Self JL, et al. Hospitalization of Adolescents Aged 12-17 Years with 
Laboratory-Confirmed COVID-19 - COVID-NET, 14 States, March 1, 2020-April 24, 2021. MMWR 
Morbidity and mortality Weekly Report 2021;70:851-7. 
9.  Jiang L, Tang K, Levin M, et al. COVID-19 and multisystem inflammatory syndrome in children and 
adolescents. The Lancet Infectious Diseases 2020;20:e276-e88. 
10.  Chemaitelly H, Ayoub HH, Coyle P, et al. Protection of Omicron sub-lineage infection against 
reinfection with another Omicron sub-lineage. medRxiv 2022;2022:02.24.22271440. 
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11.  Altarawneh H, Chemaitelly H, Ayoub HH, et al. Effect of prior infection, vaccination, and hybrid 
immunity against symptomatic BA.1 and BA.2 Omicron infections and severe COVID-19 in Qatar. 
medRxiv 2022;2022:03.22.22272745. 
12.  Lazarus R, Baos S, Cappel-Porter H, et al. The safety and immunogenicity of concomitant 
administration of COVID-19 vaccines (ChAdOx1 or BNT162b2) with seasonal influenza vaccines in 
adults: a phase IV, multicentre randomised controlled trial with blinding (ComFluCOV). 2021. 
(Accessed 28 October 2021).   
13.  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. (Accessed 28 October 
14.  Tauzin A, Gong S, Beaudoin-Bussières G, et al. Strong Humoral Immune Responses against SARS-
CoV-2 Spike after BNT162b2 MRNA Vaccination with a Sixteen-Week Interval between Doses. 
medRxiv 2021;2021:09.17.21263532. 
15.  Payne R, Longet S, Austin J, et al. Immunogenicity of standard and extended dosing intervals of 
BNT162b2 mRNA vaccine. Cell 2021;184:5699-714.e11. 
16.  BC Centre for Disease Control. Two Doses Prevent about 95 per Cent of COVID-19 Hospitalizations: 
B.C. COVID-19 Vaccine Effectiveness Results. Vancouver: BC Centre for Disease Control; 2021. 
(Accessed November 2021).
17.  National Advisory Committee on Immunization (NACI), Government of Canada. National Advisory 
Committee on Immunization (NACI) statement: Recommendation on the use of the Pfizer-BioNTech 
COVID-19 vaccine (10 mcg) in children 5 to 11 years of age. Ottawa: Government of Canada; 2021. 
(Accessed 26 November 2021).
18.  Voysey M, Clemens SAC, Madhi SA, et al. Safety and efficacy of the ChAdOx1 nCoV-19 vaccine 
(AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, 
South Africa, and the UK. The Lancet 2021;397:99-111. 
19.  Liu X, Shaw RH, Stuart ASV, et al. Safety and immunogenicity of heterologous versus homologous 
prime-boost schedules with an adenoviral vectored and mRNA COVID-19 vaccine (COM-Cov): a 
single-blind, randomised, non-inferiority trial. Lan
under  cet 2021;398:856-69. 
20.  Chiu N-C, Chi H, Tu Y-K, et al. To mix or not to mix? A rapid systematic review of heterologous 
prime–boost COVID-19 vaccination. Expert Review of Vaccines 2021;20:1211-20. 
21.  Hillus D, Schwarz T, Tober-Lau P, et al. Safety, reactogenicity, and immunogenicity of homologous 
and heterologous prime-boost immunisation with ChAdOx1 nCoV-19 and BNT162b2: a prospective 
cohort study. Lancet 2021;9:1255-65. 
22.  Schmidt T, Klemis V, Schub D, et al. Immunogenicity and reactogenicity of heterologous ChAdOx1 
nCoV-19/mRNA vaccination. Nat Med 2021;27:1530-5. 
23.  Normark J, Vikström L, Gwon YD, et al. Heterologous ChAdOx1 nCoV-19 and mRNA-1273 
vaccination. New England Journal of Medicine 2021;385:1049-51. 
24.  Powell A, Power L, Westrop S, et al. Real-world data shows increased reactogenicity in adults after 
heterologous compared to homologous prime-boost COVID-19 vaccination, March−June 2021, 
England. Eurosurveillance 2021;26:2100634. 
25.  Shaw RH, Stuart A
document  , Greenland M, et al. Heterologous prime-boost COVID-19 vaccination: initial 
reactogenicity data. The Lancet 2021;397:2043-6. 
26.  Gram MA, Nielsen J, Schelde AB, et al. Vaccine effectiveness when combining the ChAdOx1 vaccine 
as th
This  e first dose with an mRNA COVID-19 vaccine as the second dose. medRxiv 
27.  Nordström P, Ballin M, Nordström A. Effectiveness of heterologous ChAdOx1 nCoV-19 and mRNA 
prime-boost vaccination against symptomatic Covid-19 infection in Sweden: A nationwide cohort 
study. Lancet Regional Health Europe 2021;11:100249. 
28.  Vinh D, Gouin J-P, Cruz-Santiago D, et al. Real-world serologic responses to extended-interval and 
heterologous COVID-19 mRNA vaccination in frail elderly: interim report from a prospective 
observational cohort study. medRxiv 
Last updated: 
29 April 2022 
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