May the fourth be, well, different

By Megan Brodie 2 years ago | In Vaccines
  • 2 years ago

11 July 2022

As millions more Australians become eligible for a fourth Covid vaccine from today (Monday), many are asking which of the four provisionally approved vaccines available in Australia will give them the best result.

University of Queensland vaccine expert Dr Paul Griffin told MedNews a ‘mix and match’ strategy could be beneficial – although, he said AstraZeneca’s adenovirus vaccine VAXEVRIA was not an option he would recommend as a booster.

Instead, he said Novavax’s NUVAXOVID protein vaccine – now widely available in Australia and approved as a booster at the start of June – was likely to be a good choice for many, particularly those who have already had two or three mRNA vaccines.

“The key message here is whichever vaccine people can get first is probably the best, but there may well be some benefit to switching across for heterologous booster, or what some people refer to as a mixing and matching strategy,” Dr Griffin said.

Dr Paul Griffin

“If people have had, for example, mRNA vaccines thus far, there may be some benefit to switching across to the protein-based vaccine of Novavax.”

Dr Griffin said the safety concerns and lower efficacy of Vaxevria meant it had little role to play as a booster dose.

“I couldn’t think of a scenario in which someone wouldn’t be able to have either an mRNA or a Novavax, so I think AstraZeneca probably has very little role to play in terms of this boosting,” he said.

“There’s also very little distinction between which mRNA. Some people have said switching from Pfizer to Moderna or vice-versa may be of benefit, but I don’t think there’s a lot of evidence to say there’s any significant difference there.

“I think we could say that there would be some benefit in switching from mRNA to protein-based vaccine if people have had, say three mRNA vaccines so far.”

Dr Griffin said Nuvaxovid “continues to demonstrate very high levels of safety and increasing data that it still works well against Omicron. It has some pretty favourable properties”.

“To use myself as an example, I had two AstraZenecas quite early. I then had a Pfizer booster then I had Novavax as my fourth dose because I was in the group with expanded eligibility at the end of May. That’s what I chose to do and that worked really well for me.”

While Moderna’s SPIKEVAX Bivalent Zero/Omicron (elasomeran/elasomeran 0) is under TGA rolling review and Pfizer has been granted a provisional determination for its COMIRNATY BIVALENT (tozinameran/riltozinameran), Dr Griffin advised against waiting.

“While these Omicron-specific booster-containing vaccines are very promising, until they’re actually approved and ready we won’t know if they’re going to be available for use.

“We know the TGA is incredibly rigorous and there are often delays even after it seems there’s enough data to support their use, and for good reason, but the simple answer is that they’re not available now.”

Dr Griffin said while the fourth dose would provide greater protection for those susceptible to the current ‘third wave’ of Omicron, it was unlikely to be the last Covid vaccine Australians receive this year, with a multivalent expected to be recommended before the year is out.

In terms of which strain of the virus is now on the rise, Dr Griffin said Omicron subvariants continue to dominate with Omicron 2.75 the latest threat, again being even more infectious than its predecessors.

He said the subvariants also vary more from each other than previous variants such as Alpha and Delta, meaning it is more likely the next threat will be a subvariant.

“We’ve seen more deaths from Omicron than we saw from all the previous variants because it’s really a numbers game,” he said.

“Proportionally, severe disease is less likely but when the case numbers go up so much, the absolute number of people with severe disease is much greater, so we need not underestimate these new subvariants.”

©MedNews 2022

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