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About the COVID-19 vaccines

14-minute read

The COVID-19 vaccine will be available to all Australians in 2021. Read about its safety, development, approval and more.

If you have severe difficulty breathing, call triple zero (000) immediately and tell the call handler and the paramedics on arrival about your recent travel history and any close contact with a person with confirmed COVID-19.

Which COVID-19 vaccines are available in Australia?

Australia’s Therapeutic Goods Administration (TGA) has provisionally approved vaccines for COVID-19:

  • Comirnaty, the Pfizer-BioNTech COVID-19 vaccine, provisionally approved for people aged 12 years and older
  • Vaxzevria, the Oxford University-AstraZeneca vaccine, provisionally approved for people aged 18 years and older
  • Janssen, the Janssen-Cilag Pty Ltd vaccine, known as Johnson & Johnson, provisionally approved for people aged 18 years and older — this vaccine is not included in Australia’s COVID-19 vaccination program
  • Spikevax, the Moderna Australia vaccine, for people aged 12 years and older

Cominarty (Pfizer) vaccine

Pfizer's Comirnaty vaccine is an mRNA vaccine. People need to receive 2 doses of the Pfizer vaccine, given at least 21 days apart. The minimum acceptable interval between the 2 doses is 19 days. If this isn’t possible, it is recommended to complete the 2-dose course within 6 weeks.

It is not recommended to repeat a vaccine dose if the interval between doses is less than 19 days.

You can read the consumer medicines information leaflet (CMI) for this vaccine here.

The Australian Technical Advisory Group on Immunisation (ATAGI) recommends that Pfizer is the preferred vaccine for people aged 59 and under. People aged 18 and over who've already had their first dose of AstraZeneca’s Vaxzevria vaccine without any adverse effects can have a second dose of AstraZeneca.

Vaxzevria (AstraZeneca) vaccine

AstraZeneca’s Vaxzevria vaccine is a viral-vector vaccine. ATAGI recommends that AstraZeneca is the preferred vaccine for people aged 60 years and older. You can read the consumer medicines information leaflet (CMI) for the AstraZeneca vaccine here.

People also need to receive 2 doses of the AstraZeneca vaccine. The second dose should be given 4 to 12 weeks after the first dose.

In areas where there are no coronavirus outbreaks, ATAGI recommends that the preferred interval between doses of the AstraZeneca vaccine remains at 12 weeks. In areas where there is a significant COVID-19 outbreak involving the Delta variant:

  • an interval of between 4 and 8 weeks is preferred
  • it’s recommended that adults aged 59 and under who do not have immediate access to Pfizer’s vaccine reassess the benefits of vaccination with AstraZeneca versus the rare risk of a serious side effect

Spikevax (Moderna) vaccine

Moderna’s Spikevax vaccine is an mRNA vaccine. The Moderna vaccine is recommended for people aged 12 to 59 years. It’s recommended that the Moderna vaccine is given in 2 doses that are administered 28 days apart.

Other vaccines

The Australian Government also has agreements to secure the following vaccines:

  • Novavax — this vaccine has been given provisional determination by the TGA, and if granted provisional approval, it’s anticipated that 51 million doses will be available in Australia. You’ll likely need 2 doses.
  • COVAX facility — this is a global initiative that will provide access to COVID-19 vaccines when they become available. If approved, it’s anticipated that 25 million doses will be available to the Australian population.

Why are the Pfizer and Moderna vaccines preferred for people aged 59 and under?

There is a link between the AstraZeneca vaccine and a very rare condition called thrombosis with thrombocytopenia syndrome (TTS). The risk of this occurring is slightly higher in younger adults than in older adults. TTS typically occurs around 4 to 42 days after AstraZeneca vaccination and can be treated very effectively.

Therefore, the Australian Technical Advisory Group on Immunisation (ATAGI) recommends that the Pfizer and Moderna vaccines are the preferred vaccines for people aged 59 and under.

However, if you’re aged 18 to 59 years, you can have the AstraZeneca vaccine if you’ve weighed up the benefits and the risks, and you provide informed consent.

For more information about the Pfizer vaccine, go to Who is eligible for COVID-19 vaccination?

Are COVID-19 vaccines safe?

All vaccines are thoroughly tested for safety before they’re approved by the Government’s therapeutic regulatory body, the Therapeutic Goods Administration (TGA), for use in Australia.

As part of the Australian Government’s Department of Health, the TGA is responsible for regulating all therapeutic goods, including prescription medicines, vaccines, sunscreens, vitamins and minerals, medical devices, blood and blood products. Testing involves carefully analysing clinical trial data, ingredients, manufacturing processes and other factors.

Even after you receive a vaccine, it’s still monitored for safety.

If you have any questions about vaccination, talk to your doctor, nurse or other healthcare professional. They can also give feedback to the TGA about any side effects — even if they’re minor. This will help the TGA oversee the safety of vaccines. In the unlikely event that a safety risk develops, the TGA will inform healthcare providers, the community and the Australian Government as soon as possible.

How are vaccines approved in Australia?

Before a COVID-19 vaccine becomes available in Australia, it must pass the rigorous approval processes of the Therapeutic Goods Administration (TGA). This includes assessing every ingredient in the vaccine for safety, quality and effectiveness.

A clinical trial is a scientific study conducted by the makers of a vaccine. Clinical trials of medicines are done in phases.

The TGA carefully assesses the results of clinical trials, as well as the way in which the trials were run. The TGA also checks that the trials involved enough human participants that represented the people for whom the vaccine is intended.

The TGA ensures that vaccine manufacturers meet manufacturing quality standards. TGA laboratories assess the quality of every batch of a vaccine before it can be supplied in Australia.

Sometimes a ‘provisional approval pathway’ is needed for the temporary registration of promising new medicines and vaccines — where the need for early access outweighs any risks.

The TGA has provisionally approved the Pfizer, AstraZeneca, Janssen-Cilag and Moderna vaccines. The Janssen vaccine is not included in Australia’s COVID-19 vaccination program.

It’s expected that other makers of COVID-19 vaccines will apply to the TGA for registration using this provisional approval pathway.

Video provided by Australian Government Department of Health

What is a vaccine?

Vaccination prepares the immune system to fight against a future infection. Vaccines often contain tiny amounts of dead or weakened viruses or bacteria, called antigens. The immune system responds to these antigens without you getting sick, effectively training the immune system to fight the disease if exposed to it in the future.

Some vaccines need to be given more than once — known as ‘booster’ vaccinations. Some vaccines, such as the seasonal influenza (flu) vaccine, only work for a short period of time. This is because the virus itself can change over time.

Vaccines are usually given with an injection.

Video provided by Australian Government Department of Health

What ingredients are in a vaccine?

The ingredients of a vaccine vary, depending on what the vaccine is for. A vaccine may contain some of these ingredients:

  • a protein component of a virus
  • a piece of genetic code (DNA or mRNA)
  • a very small dose of a weakened virus
  • a substance to boost the immune response (known as an adjuvant)
  • sterile salt water (saline) for injections
  • a small amount of preservative or stabilisers, which ensure vaccines stay effective during storage and transportation

Once a COVID-19 vaccine has been approved by the Therapeutic Goods Administration (TGA), its ingredients will be listed in the Australian Register of Therapeutic Goods.

How do different COVID-19 vaccines work?

Vaccines train your immune system to quickly recognise and get rid of the bacteria or viruses that can cause serious illnesses. There are many types of vaccine being developed to protect us against COVID-19. They’re all designed to generate an immune response specific to the COVID-19 coronavirus.

Most COVID-19 vaccines use the coronavirus ‘spike’ protein to cause this immune response. The immune system recognises this spike protein as ‘foreign’ and starts producing long-lasting immune cells and antibodies.

If a vaccinated person becomes exposed to COVID-19 later on, the immune system will be able to launch a faster and better response to protect against the disease.

Important: these vaccines do not contain the live or whole virus that causes COVID-19.

Here’s how the common types of COVID-19 vaccine work.

Messenger RNA (mRNA)

The Pfizer and Moderna vaccines are examples of an mRNA vaccine. This vaccine uses a genetic code, called messenger-RNA (mRNA), to trigger the production of the COVID-19-specific spike protein.

The mRNA from the vaccine enters the cytoplasm of the body’s cells. The cells then use the instructions contained in the mRNA to make the spike protein. Immune cells can then recognise the spike protein as foreign and begin building an immune response against it.

Important: messenger-RNA can’t change or interact with a person’s DNA in any way.

Clinical trials of the Pfizer vaccine show that this vaccine triggers antibodies that can respond to a range of coronavirus mutations. The Australian Government, which has approved this vaccine for people aged 12 and older, will continue to monitor this as more data becomes available.

Protein

The Novavax vaccine is an example of a protein-based vaccine. This uses a non-infectious component of COVID-19, usually the spike protein.

This protein is found on the surface of the virus and can be manufactured in a laboratory. When the vaccine enters the body, immune cells recognise the spike protein as foreign and begin building an immune response against it.

Vector

The AstraZeneca vaccine is an example of a viral vector vaccine. These types of vaccines use a harmless, weakened animal virus that contains the genetic code for a protein unique to COVID-19, usually the spike protein.

This weakened animal virus is known as a ‘viral vector’. Once the viral vector enters the body, immune cells then recognise the spike protein as foreign and begin building an immune response against it.

Do COVID-19 vaccines stop transmission of the virus?

Data from the United Kingdom and Finland show that the AstraZeneca, Pfizer and Moderna vaccines do reduce onward transmission of SARS-CoV-2 to a degree.

One UK study found that the AstraZeneca vaccine was 48 per cent effective, and the Pfizer vaccine was 46 per cent effective, at preventing onward transmission to household contacts of vaccinated people who had breakthrough infections. Another study from the UK in healthcare workers found that the Pfizer vaccine was associated with a 54 per cent reduction in transmission to household members.

A study from Finland, in healthcare workers who had received the Pfizer or Moderna vaccine, found that the vaccines were 43 per cent effective against transmission to unvaccinated household contacts.

Can I choose which vaccine I receive?

Many people won’t be able to choose which COVID-19 vaccine they receive.

  • The preferred vaccine for people aged 60 and over is the AstraZeneca vaccine.
  • The preferred vaccine for people aged 12 to 59 years is the Pfizer vaccine or the Moderna vaccine.

For more information about the Pfizer vaccine, go to Who is eligible for COVID-19 vaccination?

However, adults aged 18 to 59 years can receive the AstraZeneca vaccine if they have weighed up the benefits and the risks, and provide informed consent. Talk to your doctor or immunisation provider to help inform your decision.

Are COVID-19 vaccines interchangeable?

The Australian Technical Advisory Group on Immunisation (ATAGI) recommends using the same COVID-19 vaccine for the 2 doses needed to complete vaccination, unless someone has specific medical conditions that prevent them from receiving their full course or precautions must be taken, or the same vaccine brand is not available in Australia.

Pregnant women are a priority group for COVID-19 vaccination and should be offered the Pfizer or the Moderna vaccine at any stage of their pregnancy. Pregnant women who have already received their first dose of the AstraZeneca vaccine can receive either the Pfizer, the Moderna or the AstraZeneca vaccine for their second dose — although Pfizer or Moderna is preferred.

People who have received overseas a first dose of a COVID-19 vaccine that is not available in Australia and are due for a second dose in Australia can be offered an alternative vaccine brand to complete their course.

The recommended interval for administration of a second COVID-19 vaccine dose is 4 to 12 weeks after the first. A longer interval is acceptable if the second dose cannot be administered during this time window.

What’s the difference between a booster dose and a primary vaccine course?

A booster dose refers to an additional vaccine dose after you’ve completed the primary vaccine course.

Booster doses are recommended for those 18 years and older who’ve had 2 doses of a COVID-19 vaccine for their primary vaccination course at least 6 months ago.

Getting a booster dose is not mandatory, but to maintain protection against COVID-19, it’s recommended that most people have a booster dose.

A primary COVID-19 vaccine course consists of 2 doses of the following COVID-19 vaccines available in Australia: Comirnaty (Pfizer), Spikevax (Moderna) or Vaxzevria (AstraZeneca); or 1 dose of the Janssen COVID-19 vaccine — also known as Johnson & Johnson (which is registered, but not available, in Australia).

Mixed schedules of these vaccines are also included in the definition of an acceptable primary course, as are additional TGA-recognised vaccines.

For people with severe immunocompromise, a primary course is defined as 3 doses of a COVID-19 vaccine.

How have the COVID-19 vaccines been developed so quickly?

The urgency of the pandemic has meant that all available resources and efforts have been directed towards finding effective vaccines.

Globally, some COVID-19 vaccines were approved and administered just 12 months after the virus was discovered. Usually, development of a vaccine takes several years. Some of the reasons behind this rapid progress include:

  • The levels of funding and collaboration between vaccine developers and governments are greater than ever before. Planning began early, including investment in manufacturing facilities before a vaccine was even available.
  • Technology makes vaccine development faster than in the past. To develop a vaccine, scientists need to understand the virus’s genetic code. New technology allowed researchers to quickly identify the genetic code of the COVID-19 virus soon after it emerged. This allowed scientists around the world to start designing and building vaccines.
  • Clinical trials progress more quickly if a disease is widespread, which is the case for COVID-19 in many countries. This means researchers can evaluate the effect of a vaccine on both unvaccinated and vaccinated groups much sooner than they’d be able with a rare disease.

For more information on the Australian Government’s COVID-19 vaccine strategy, go to health.gov.au and click on ‘COVID-19 vaccines’.


More questions about COVID-19 vaccines

Click on the links below for more questions and answers about COVID-19 vaccines.


Resources in other languages

COVID-19 vaccination resources in other languages are available from the Department of Health.

Looking for more information?

Visit healthdirect's COVID-19 information hub for more answers to questions about the coronavirus, including vaccinations and restrictions.

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Last reviewed: November 2021


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