Q&A: How does Novavax work, can it be mixed with other vaccines and is it a booster? - expert explains

Vaccine Alliance Aotearoa NZ executive director Dr Fran Priddy has been working in the field of infectious diseases and the development of vaccines for over 20 years. Photo / Supplied

This week marks the rollout of the newly approved vaccine Novavax in Northland, offering an alternative to Pfizer and AstraZeneca. But where does this different vaccine come from and how does it work? The Northern Advocate spoke with the executive director for the Vaccine Alliance Aotearoa New Zealand, Dr Fran Priddy, about the development and efficacy of Novavax. Dr Priddy has over 20 years of experience in emerging infectious disease vaccine development, vaccine clinical trials and international health.

Q: What do you think about Novavax?

A: It's a very good vaccine. It appears to be very safe and it's a technology we already know. It's great to have another vaccine available that can hopefully be used for people who are not vaccinated yet for whatever reason. I'm glad it's in New Zealand and I think it's a vaccine that will stick around for a while.

Q: What makes it different to other vaccines?

A: The Novavax vaccine is based on a well-known vaccine technology which is a protein vaccine together with an adjuvant. That kind of vaccine has been used for a long time for other infectious diseases safely and successfully.

It's different in the way that it's using a new adjuvant. An adjuvant is something that stimulates your immune system to get a better response. Novavax, the US-based company, has developed its own adjuvant.

It's not an mRNA vaccine, like Pfizer, and it's not a viral vector vaccine, that's what AstraZeneca is. But all these vaccines are based on the virus's spike protein.

Q: So what is a protein vaccine?

A: Protein vaccines are based on a piece of protein from the bacteria or virus. In the case of Covid, the Novavax vaccine is using the spike protein.

But it's not just one spike protein. Instead, they produce different spike proteins and assemble them in a nanoparticle. You can imagine a bunch of these spike proteins stuck together in a flower shape. To the body that looks like a virus because the virus is a bubble with a bunch of spikes sticking off it.

Each shot of the vaccine is made out of many of these nanoparticles and the adjuvant mixed together. It's a jazzed-up version of the traditional protein vaccine – a higher-tech version.

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Q: What is known about the trials and how well am I protected if I get Novavax?

A: In the studies, they saw a great antibody and T-cell response. They found protection against symptomatic disease and also severe disease.

Novavax is 85 per cent effective (90 per cent in one trial and 83 per cent in another trial) in preventing symptomatic disease. It was 100 per cent effective in preventing severe disease. No one was hospitalised in any of these trials. The trials had around 15,000 participants each. That's huge.

There were two big trials, in Mexico and in the UK. They also tested the vaccine in South Africa and Australia. The trials that showed the efficacy were done when Alpha was circulating. There may have been some Delta but it was definitely pre-Omicron.

But when we talk about the Pfizer vaccine being 95 per cent effective that was again Alpha. In the lab, Novavax gives good protection against Omicron. But they don't have the data in humans to show this yet.

Q: How safe is it?

A: The safety data was standard for a modern vaccine. There has not been any evidence of serious safety issues like myocarditis. Though there have not been enough people receiving Novavax to know for sure whether you might have some of the more serious effects. When you start a new vaccine, you have to give it time to see if there might be future adverse events that we're not aware of. But anything common would have shown up already.

Q: How many shots do people need and can we mix the different vaccines?

A: It's approved for two shots, similar to other vaccines. They have done trials where people initially received an mRNA and then a Novavax shot. The reaction didn't look very different – there are no new safety findings per se but again the numbers aren't in the millions and millions. There is biologically speaking no problem. And there is reason to think it could even give you a better immune response.

Q: Can I get Novavax as a booster?

A: It's not approved here as a booster. It is approved as a booster for limited use in other countries, in Australia, for example. The data on how effective their booster is on maintaining protection is coming out sometime this year. Once Novavax has that information and shares it with New Zealand it could be approved. It's the same for adolescents under 18.

Novavax infobox

1. NZ has an initial supply of 250,000 doses and will only be available at a limited number of sites. If there is demand, the distribution might be ramped up.
2. Novavax can be mixed with Pfizer or AstraZeneca but a prescription is required.
3. Novavax currently doesn't meet the Government's vaccine mandate regulations.
4. To book in for a Novavax shot, visit BookMyVaccine.nz or call the Covid Vaccination Healthline on 0800 28 29 26 (8am-8pm, 7 days a week).