These two vaccines are in addition to supply arrangements for vaccines from Oxford University/AstraZeneca and the University of Queensland/CSL, announced in September.
Australia will also have access to vaccines via the World Health Organisation-backed COVAX initiative.
However, these arrangements depend on whether the vaccines are shown to be safe and effective in clinical trials, which are still ongoing.
So what do we know about the two vaccines in this latest deal?
What do we know about the Novavax vaccine?
The Novavax vaccine, NVX-CoV2373, contains purified pieces of the spike protein of SARS-CoV-2, the virus that causes COVID-19.
These proteins are administered with an adjuvant, a molecule that enhances the immune response.
The idea is that when this vaccine is administered, the body recognises its contents as ‘foreign’ and mounts a protective immune response.
Early clinical trials were performed in Australia. In the phase one clinical trials, the vaccine was generally well-tolerated and produced strong antibody responses — stronger than what we see in patients recovering from COVID-19.
In September, Novavax launched a phase three clinical trial in the United Kingdom. Further large-scale clinical trials are planned for other countries in late-2020 and early-2021.
If the Novavax vaccine is successful, 40 million doses are expected to be available in Australia during 2021, with the option to buy a further 10 million.
What do we know about the Pfizer vaccine?
The vaccine developed by Pfizer, BNT162b2, is based on the genetic material mRNA (or messenger ribonucleic acid). Such mRNA vaccines carry a piece of genetic material that codes for viral proteins, or parts of them.
Once inside your cells, the mRNA instructs your cells’ protein factories to make copies of these viral proteins. These then stimulate your immune system to mount a protective immune response.
Pfizer’s BNT162b2 vaccine codes for the virus’ full-length spike protein.
When older adults (65–85 years of age) were vaccinated, they produced a greater neutralising antibody response than seen in patients who contracted SARS-CoV-2 naturally.
Interestingly, BNT162b2 is one of the first COVID-19 vaccines to be tested in adolescents (12–18 years of age).
In July, Pfizer announced the launch of large-scale phase two and three trials. Trials are underway in several countries, including the United States, Germany, Argentina, Brazil and South Africa, involving 44,000 participants.
One of the challenges facing this vaccine is distribution, as it needs to be stored below -70℃. This is costly and makes transportation difficult, particularly in developing regions.
What happens next?
Both vaccines, if successful in clinical trials, will be manufactured outside Australia.
This will allay fears Australia might miss out on mRNA vaccines as the country does not have the technology and capacity to make these vaccines itself.
A successful COVID-19 vaccine will also need to navigate the rigorous assessment and approval processes of the Therapeutic Goods Administration for use in Australia.
Hedging our bets
It is unlikely all COVID-19 vaccines currently in development will be successful.
We have already seen COVID-19 vaccine trials temporarily halted due to safety issues.
And not all vaccines will provide a consistent level of immunity. Some vaccines may only provide immunity for limited periods of time and require a booster shot.
By investing in numerous front-running candidates, the Australian government’s strategy of not putting all its eggs in one basket is a wise one.
Investing in a range of vaccine technologies also has benefits, should more than one vaccine become available. This is because different vaccine technologies may be more effective or safe in different populations.
This increases the likelihood that all sections of society — young and old, with or without existing medical complications — could be targeted.