COVID-19 vaccine booster doses

A booster dose is an extra dose of a vaccine after the primary course of two doses has been given.¹

Booster doses are common for some vaccines given as part of the National Immunisation Program (NIP) Schedule, such as diphtheria, tetanus and pertussis (whooping cough).²

Table 1: Primary COVID-19 vaccine course definitions in Australia^a,1

^a_{The definition of an acceptable primary course includes mixed schedules of these vaccines, as well as TGA-recognised vaccines}

Find out more about vaccines and COVID-19.

In Australia, there are five vaccines with provisional approval for use as a booster dose:³

• COMIRNATY (tozinameran) – Pfizer Australia (for people aged 12 years and older)
• SPIKEVAX (elasomeran) – Moderna Australia (for people aged 18 years and older)
• SPIKEVAX Bivalent Original/Omicron (elasomeran/imelasomeran) – Moderna Australia (for people aged 18 years and older)
• VAXZEVRIA – AstraZeneca (for people aged 18 years and older)
• NUVAXOVID (NVX-CoV2373) – Biocelect on behalf of Novavax (for people aged 18 years and older)

The Australian Technical Advisory Group on Immunisation (ATAGI) recommends first booster doses for all Australians aged 16 years or older. This will help keep immunity to the virus at high levels¹ and help keep people protected as new strains of the COVID-19 virus emerge.

ATAGI has reviewed evidence on the benefits and risks of a booster dose of Pfizer COVID-19 vaccine in adolescents in Australia aged 12-15 years. Current data suggest that COVID-related serious illness is very rare in healthy adolescents aged 12-15, particularly after completion of a primary series of COVID-19 vaccination.⁴

On 9 June 2022, ATAGI recommended that a first booster dose of Pfizer COVID-19 vaccine may be given to adolescents aged 12-15 years who have had all their primary vaccine doses at least 3 months ago and:

• are severely immunocompromised
• have a disability with significant or complex health needs
• have complex and/or multiple health conditions that increase risk of severe COVID-19.⁴

Boosters are not currently recommended for 12-15 year-olds outside of the above groups. ATAGI will continue to review international evidence on efficacy of a booster in this age group.

The messenger RNA (mRNA) vaccines (Pfizer or Moderna) are the ATAGI preferred vaccines for booster doses, noting the Pfizer COVID-19 vaccine is the only registered vaccine for use in people aged 12-17 years. It doesn't matter which vaccine you got for your primary course.^1,5 The mRNA vaccines appear to work better as a booster dose compared with other COVID-19 vaccines. A study has shown they give the highest boost in antibodies compared with AstraZeneca, when given as a booster dose.^1,6

VAXZEVRIA (AstraZeneca) and NUVAXOVID (Novavax) can be given as a booster dose for people aged 18 years and older if they are unable to receive one of the mRNA vaccines or no other COVID-19 vaccine is suitable.¹ For example, people who can’t receive an mRNA vaccine due to allergic reactions or myocarditis.¹ Myocarditis is a disease that causes the heart muscle to become inflamed.⁷ Myocarditis and pericarditis are known reactions in a small number of people who receive mRNA COVID-19 vaccines.¹

SPIKEVAX Bivalent Original/Omicron (Moderna) can be given as a booster dose for people aged 18 years and older. It is the first bivalent COVID-19 vaccine approved for use in Australia. This means the vaccine triggers an immune response against two different COVID-19 variants: the original virus and the BA.1 Omicron variant. 

Find out more about booster doses for COVID-19 vaccines from the Australian Government Department of Health.

Staying up to date

It is important to stay up to date with your COVID-19 vaccination. Booster doses are not mandatory but are highly recommended to ensure you have the highest protection you can get. Your digital vaccination certificate is updated when you receive each dose of vaccine. This includes any booster doses.⁸

If you are 16 years of age or older, an up to date COVID-19 vaccination status requires:⁹

• completing a primary course, and
• getting a booster dose at least 3 months after the primary course, and before 6 months.

If you didn’t get a COVID-19 vaccine booster dose before 6 months, it is still safe and effective to get it at any time after 6 months. This will make you up to date.⁹ You should get the booster dose in the advised timeframe for your age or health status. If not, your status is overdue.⁸

What is the difference between a third dose and a booster dose?

ATAGI recommends a third dose of the COVID-19 vaccine as part of the primary course if you are aged 5 years or older and severely immunocompromised. This will help boost your immune response.¹⁰

A booster dose is an extra dose of a vaccine. You receive it after the primary course, as protection against infection decreases over time.¹

You can still receive a booster dose after getting your third dose. If you are 16 years of age or older with severe immunocompromise, you should get the booster dose 3 months after the third primary dose. This is in line with the timing for the general population.¹

You can get a booster dose if you:¹

• are 16 years of age or older, and
• have finished your primary vaccine course at least 3 months ago.

If you are severely immunocompromised, you can get a booster dose 3 months after you finish your 3-dose primary course.¹

If you are pregnant, you can get a booster dose 3 months after you finish your primary course.¹

Children aged under 16 years are not recommended to get a booster dose. Severe COVID-19 is not common in this age group. The primary course generates a strong immune response. Current evidence suggests the benefits from booster doses in children are likely to be small.¹¹

You can get either the Pfizer or Moderna vaccine as a booster dose. It doesn’t matter which vaccine you received for your primary course.^1,5 Studies have shown that mixing COVID-19 vaccines for the primary course is safe. It triggers a similar, or improved, immune response.^12,13

ATAGI recommends an additional booster dose (winter booster dose) to increase vaccine protection before winter for people who are at the greatest risk of severe illness from COVID-19.¹⁴

You can get an winter booster dose if you have received your primary course and first booster and if you are:¹⁴

• aged 50 years or older
• a resident of an aged care or disability care 16 years or older and a resident of an aged care or disability care facility
• 16 years or older and severely immunocompromised
• Aboriginal or Torres Strait Islander and aged 50 years and older
• 16 years or older with a medical condition that increases the risk of severe COVID-19 illness
• 16 years or older with a disability.
  

ATAGI has advised people aged 30 to 49 years old can receive a fourth dose if they choose.

The additional booster dose can be given from 3 months after you have received your first booster dose. If you have a confirmed COVID-19 infection after getting your first booster, you should get your additional booster dose from 3 months after the confirmed infection, as infection can boost immunity.¹⁴

Everyone aged 5 years and over should wait 3 months between testing positive for COVID-19 and their next recommended vaccine dose. ^5,11 This includes primary vaccine doses or a booster dose.

You should get your winter booster dose (if eligible) from 3 months after a confirmed COVID-19 infection if the infection occurred after your first booster dose.^14,15

People who receive a booster have lower rates of COVID-19 infection, as well as lower chances of hospitalisation, severe disease and death from a COVID-19 infection, compared with those in people who do not receive a booster dose.^16-19

Booster doses also trigger improved immune responses^20-22 and boosted immunity.⁶

Boosters are an important prevention option for most people over the age of 16 years and are especially helpful for:^1,23

• people at a greater risk of severe COVID-19 infection, including those:
  • aged ≥ 50 years
  • with underlying medical conditions
  • living in aged care facilities
  • Aboriginal and Torres Strait Islanders
• people at high job-related risk of COVID-19, and
• people living in areas where there is active spread.

The expected benefits of getting a booster dose at 3 months are:¹

• a low chance of illness with symptoms from COVID-19 caused by current strains
• a low chance of severe illness from COVID-19 caused by current strains
• a low chance of death from COVID-19 caused by current strains, and
• lowered impacts on the healthcare system, combined with improved public health and social measures.

Although COVID-19 vaccines work well,²⁴ protection against COVID-19 wanes over time.²⁵ A booster dose will help you strengthen your immunity against COVID-19. It will make sure the protection you get from the primary course is even stronger and longer lasting. It will also help prevent spread of the virus.⁵

Studies have shown booster doses lower the risk of infection and the risk of decreasing immunity in the short term.^26,27 Effectiveness against severe illness and hospitalisation decreases 4 months after a booster dose.²⁸ However, duration of protection from a booster dose is currently unclear because infection is mostly being caused by the SARS-CoV-2 Omicron BA.4 and BA.5 subvariants. These subvariants can partly escape the immune response generated by both prior vaccination and infection.

Booster doses of mRNA vaccines are safe and well tolerated.^20,21 Some people have unwanted effects after taking a medicine or vaccine. These are also called side effects or adverse events.

Side effects from booster vaccines are generally mild or moderate.²⁹ The most common ones are feeling tired, headache, joint stiffness and muscle pain.²⁰

A UK study has reviewed the safety of the AstraZeneca, Moderna and Pfizer vaccines as booster doses. When given at least 70 to 84 days after a primary course, there were no safety concerns for any of the vaccines.⁶

If someone experienced side effects, these were usually reported the day after the booster dose. The types of side effects were similar to those reported after the second dose of the primary course.³⁰

Serious side effects such as myocarditis and pericarditis can happen following a booster dose of the Pfizer or Moderna vaccine but they appear to be rare. Australian and international data on these side effects currently shows that myocarditis and pericarditis following vaccination with an mRNA vaccine are less common after the booster dose, compared with a second dose. 

You can get your booster dose at the same time as other non-COVID-19 vaccines. This includes the flu vaccine.^1,11

You can still contract and spread COVID-19 even after a booster dose, but breakthrough (recurrent) infections are far less likely to be serious. It may make you less likely to spread breakthrough infections. This is due to lower amounts of the virus in your body (viral load) following a booster dose.²⁷

Studies have shown the chance of you getting COVID-19 after completing a primary course is much lower than for unvaccinated people.³¹ Breakthrough infections in vaccinated people have lower viral loads than those in people who are unvaccinated. This effect starts to decline after 2 months. It vanishes 6 months or longer after vaccination. A booster dose restores this effect on reducing breakthrough infection viral loads.²⁷

You should still get tested as soon as you can if you have cold or flu-like symptoms, even if they are mild.

Find out more about COVID-19 symptoms and how to get tested.

We know from studies that booster doses are very good at protecting us against severe disease from current strains.^20,22 This includes the Beta, Gamma and Delta strains.²⁰ However, there is not enough evidence to determine their efficacy against future strains.

A booster dose of an mRNA vaccine following a primary course of two doses triggers a stronger immune response against the COVID-19 virus compared with two doses, including the Delta and Omicron strains.^32,33

A booster dose with an mRNA vaccine is 80–95% effective against hospitalisation due to the Omicron strain for the first 3 months. It is 75–85% effective at 4–6 months. It is 85–99% effective against death due to the Omicron strain for the first 3 months.³⁴

An additional booster dose has been recommended before winter for those who are at the greatest risk of severe illness from COVID-19.¹⁴ The additional winter booster dose can be given from 3 months or longer after an individual has received their first booster dose. If someone has COVID-19 after their first booster, they can get the additional booster from 3 months after the confirmed infection.¹⁴

Our knowledge about COVID-19, the effect of vaccines and the different strains is still growing. This means ATAGI will keep updating its recommendations for the COVID-19 Vaccination Program.

Not all vaccines give lifelong immunity. The influenza vaccine, for example, is usually given every year. Other vaccines, such as the polio vaccine, may also need booster doses to help keep you protected from infection.³⁵

• Find out more about COVID-19 vaccines on the Department of Health website
• Find out more about COVID-19 vaccine boosters in your language