FOI 3687 Document 2.pdf

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
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•
Recommended and variations on vaccination schedule
•
Minimum valid dose schedules
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•
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.
Information
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
immunocompromised.
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.
the
In Australia, vaccination is strongly recommended for the following groups:
under
•
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
released
•
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
document
Adults aged under 60 years
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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.
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For information on third primary doses for severely immunocompromised individuals
see: Considerations for special populations – people who are immunocompromised.
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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.
Information
of
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.
the
Booster dose recommendations
under
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
released
groups, from 4 months after the first booster dose:
was
•  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
booster.
This
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
example:
•  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
individual.
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.
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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.
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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,
including:
Information
•  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.
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The evidence underpinning booster dose recommendations will continue to be reviewed and this
clinical guidance may be refined.
the
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.
document
For more information on booster doses, see:
This
•  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.
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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
Information
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.
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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
population
•  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.
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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
•
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medical management
•  other factors.
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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
immunocompromise.
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.
Act
Children and adolescents
COVID-19 vaccination is recommended for all children and adolescents aged 5 years or older.
Children aged 5 to 11 years
Information
of
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
the
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
children.
released
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.
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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.
document
AstraZeneca and Novavax vaccines are not registered for use in children aged 5 to 11 years.
Adolesce
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
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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:
Act
•  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
outcomes.6,7
Adolescents and children are accounting for increasing proportions of COVID-19 cases, in the context
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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
the
Vaccinating children and adolescents is anticipated to prevent:
under
•  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
syndrome9
released
•  post-COVID-19 condition (‘long COVID’).
was
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.
document
Pregnancy, breastfeeding or planning pregnancy
This
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
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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.
Information
of
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.
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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.
was
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).
This
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.
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There is limited evidence on the safety and effectiveness of co-administering COVID-19 vaccines at
Act
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.
of
Co-administration of antipyretics or analgesics
Using paracetamol or ibuprofen before receiving a COVID-19 vaccine is not recommended.
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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.
the
Recommended and variations on vaccination schedule
under
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
released
manufacturer’s recommended dosing schedule for
paediatric Pfizer vaccine is 2 doses, 3 weeks apart; and for Moderna vaccine, 2 doses, 4 weeks apart.
was
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
This
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
interval
•  local epidemiology
•  individual circumstances including underlying risk of COVID-19 to the child and parental
wishes.
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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.
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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
Information
administered later than the recommended interval, no further doses are recommended.
of
Pfizer and Moderna COVID-19 vaccine dosing interval for adolescents and
adults
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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
vaccines.
released
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
document
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.
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AstraZeneca COVID-19 vaccine dosing interval
Act
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.
of
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
the
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.
under
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
released
short time, and the person is still likely to have good protection.
was
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
document
Also see vaccine information – clinical guidance for more details.
This
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
weeks.
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.
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Shorter dose intervals
Act
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.
Information
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
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If the second dose of Novavax is administered later than the recommended interval, no further doses
the
are recommended.
Minimum valid dose schedules
under
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).
released
Use of an additional COVID-19 vaccine dose as a replacement dose if the
was
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.
document
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
recommend
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
sooner
•  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
immunocompromise).
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.
Act
These recommendations do not apply to booster doses.
Mixed (heterologous) schedules
Information
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.
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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.
under
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.
was
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
This
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
1982
recommended for the second dose (if not contraindicated).
Act
Children who turn 12 after their first dose of paediatric Pfizer or Moderna
vaccine
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
Information
vaccine course.
of
People with serious vaccine-attributable adverse events after dose 1 that
warrant the use of an alternative vaccine brand for dose 2
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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
under
•  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,
AND
released
•  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
was
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:
document
•  require hospitalisation (for example, thrombosis with thrombocytopenia following the first
dose
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.
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People given an incomplete course of a COVID-19 vaccine brand that is not
available in Australia
Act
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.
Information
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.
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Further reading
the
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
under
2 August 2021 (Accessed 9 September 2021). https://www.health.gov.au/news/atagi-statement-
regarding-covid-19-vaccines-in-the-setting-of-transmission-of-the-delta-variant-of-concern
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
released
vaccine effectiveness and immune response among individuals in clinical risk groups. 2021. (Accessed
12 August
2021). https://khub.net/d
was ocuments/135939561/430986542/RCGP+VE+riskgroups+paper.pdf/a6b54cd9
-419d-9b63-e2bf-5dc796f5a91f
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). https://doi.org/10.1101/2021.06.14.21258906
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). https://ssrn.com/abstract=3931758
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
2021). https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-2021-10-20-21/02-influenza-
izikson-508.pdf
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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.
Act
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). http://www.bccdc.ca/about/News-Stories/Stories/2021/Covid-19-Vaccine-
Effectiveness-Results
Information
17.  National Advisory Committee on Immunization (NACI), Government of Canada. National Advisory
of
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). https://www.canada.ca/en/public-
health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-
use-covid-19-vaccines/pfizer-biontech-10-mcg-children-5-11-years-age.html
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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,
the
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.
released
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.
was
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
2021:doi.org/10.1101/2021.07.26.21261130.
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 2021:doi.org/10.1101/2021.09.16.21263704.
Last updated:
29 April 2022
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