Mix vaccine boosters to protect against new variants

This article was consistent with advice from the WA Department of Health at the time of publication. The updated advice of the Australian Technical Advisory Group on Immunisation recommends the Pfizer vaccine is the preferred vaccine for adults under the age of 60.

Associate Professor Chris Blyth is currently co-chair of the Australian Technical Advisory Group on Immunisation, Australia’s peak scientific committee on immunisation. Associate Professor Blyth is a clinician scientist with the Division of Paediatrics in the UWA Medical School, Co-Director of the Wesfarmers Centre of Vaccines and Infectious Diseases  at the Telethon Kids Institute, an Infectious Diseases Physician at Perth Children’s Hospital, and a Clinical Microbiologist at PathWest Laboratory Medicine. He is a member of the COVID-19 Vaccine and Treatments for Australia Science and Industry Technical Advisory Group.

Will it be possible to mix and match future vaccine boosters to protect against new variants (eg. those who were vaccinated with AstraZeneca later having a Moderna booster)? What research has been done into the safety and effectiveness of this so far?
“From what we know about the COVID-19 virus, it will continue to change and so it is highly likely that boosters will be required in the future. What we don’t know yet is how frequent and what will be the most effective type of booster.

There may be real benefit in having a booster with an alternative product to your primary vaccine course and that may actually give you a much stronger protection in the long term.

Associate Professor Chris Blyth

A number of studies are ongoing by different research groups and pharmaceutical companies looking at different ways to generate booster vaccines, including against some of the new variant strains. It is likely that we will recommend a different booster to your original primary vaccine course. 

There may be real benefit in having a booster with an alternative product to your primary vaccine course and that may actually give you a much stronger protection in the long term.

Being vaccinated by one vaccine – for example a Pfizer or AstraZeneca vaccine – absolutely does not preclude you from being vaccinated with an alternative product in the future. At the very moment, we don’t yet know what that best product is for this purpose.

There are international studies trialling new vaccines to target the variants. These are being tested in people to see what the immune response is like in those who have and haven’t yet been vaccinated.

We are concerned about all current variants. The major variants we are concerned about at the moment are the UK, the South African, the Brazilian and the Indian variants. We also know that new variants will continue to evolve.

Currently, we are most concerned about how effectively the vaccines will work against the South African and Indian strains. The effectiveness of our current vaccines to different variants will need to be watched very closely.”

Australia is investigating local production of the Moderna vaccine. How safe and effective is this mRNA vaccine and who is likely to get it first? 
“The Moderna vaccine is looking like an exciting product. The published vaccine efficacy studies show that it is highly effective against disease – very similar to the vaccines we are using at the moment. 

Once it is registered in Australia, I am confident it will be a component of our broader vaccine program. Who gets it will, in part, be dependent on who is needing to be vaccinated at the time.

• Read More: Australia needs to start producing mRNA vaccines

What we do know is that Moderna has a particular focus on trying to develop vaccines against the variants and so it may be an important booster vaccine.

Local vaccine production is really important because in the setting of a pandemic we will continue to remain at risk of the impact of international markets and international supplies. If we are able to generate local production of an mRNA vaccine, I think that will significantly enhance our flexibility and our capacity to be nimble as things continue to change.”  

Are there any lessons that Australia needs to learn from Taiwan's outbreak?
“There are a couple of things we can learn from Taiwan. I think it highlights that even countries that have had things under control in 2020, are still very susceptible to outbreaks. 

We are in a world of coronavirus at the moment and we need to continually learn from that – whether it be improving our approaches to quarantine or improving the way we communicate about the Australian vaccine program.

• Read More: How do we get vaccination incentives right

Immunity is really the only thing that is going to get us out of this. The only two approaches to immunity are infection or immunisation. I think that Taiwan really highlights that we need to continue to encourage and enable people to get vaccinated.”

What is your message to those in the 50-plus age group who are thinking about whether they will take up their free AstraZeneca vaccine?

“Vaccination is necessary. We are going to need to be vaccinated to be able to stop transmission in Australia. We do not have endless time on our hands to do that and the window of opportunity is now. 

Currently, we limited COVID-19 in Australia – that is the time that we are likely to have the greatest benefit.  If we wait until we start to detect the virus, it will be almost impossible to vaccinate enough people to try and prevent significant community outbreak.”  

• Read More: Expert Series - Making sense of the COVID-19 vaccine rollout