Bivalent vaccines are the better option

New COVID variants BQ.1 and XBB now account for 10% of Victoria’s case numbers, and are expected to overtake BA.5 as the dominant Omicron variant in Australia.

Associate Professor Nick Wood of the National Centre for Immunisation Research and Surveillance and lecturer at the University of Sydney, says we don’t know if the new variants are mild or severe but that delivering boosters to patients is now a priority, and immunological evidence supports the use of bivalent vaccines.

“I would go with the variant vaccine. It certainly boosts your antibody levels against the original strain, and it also boosts you against the Omicron variant, however the effectiveness of a higher antibody level against infection and hospitalisation is not yet known,” A/Prof Wood says.

Associate Professor Nick Wood is presenting a COVID update in the upcoming Healthed webcast on Tuesday 22nd November. Register here.

Pfizer and Moderna look to be moving towards the production of bivalent vaccines only. The TGA approved the Pfizer bivalent vaccine late October, and the Moderna bivalent vaccine in August. Both target the BA.1 variant of Omicron.

“The US has gone with a BA.4/5 variant vaccine, but it will be difficult to keep changing the vaccine recipe each time the virus changes. It does feel like we’re chasing our tails and we don’t really know if there is a benefit,” says A/Prof Wood.

According to the Department of Health, 72% of the population have had three vaccine doses and around 40% have had four. Data released by NCIRS indicate that around two thirds of the population have been infected by a COVID strain.

A/Prof Wood does not expect people with hybrid immunity to be pursuing a fourth dose and the evidence does not suggest they should.

“A recent Qatar study found that three doses of the vaccine and a prior COVID infection was the best level of effectiveness. There’s no real-world effectiveness data yet on four doses and a previous infection,” he says.

“My recommendation is anyone over the age of 16 who’s had two doses will benefit from a third dose. A fourth dose is useful if you’re over 50 or have a chronic medical condition.”

As for timing of a booster shot, A/Prof Wood recommends GPs aim to deliver them in line with ATAGI recommendations.

“Next year there may be a recommendation to get both a flu shot and a COVID shot for the winter. But if between now and February or March these new sub variants really take off and cause more serious disease, there could be a rush on boosters,” he says.

For male patients aged 18 to 24 years, A/Prof Wood says the risk of myocarditis from a third booster has been found to be around 1 in 50,000, down significantly from the second dose risk, which was 1 in 10,000.

“We wanted to make sure the risk wasn’t increasing with each dose, and that appears to be the case.”

Associate Professor Nick Wood is presenting a COVID update in the upcoming Healthed webcast on Tuesday 22nd November. Register here.