“[Eris] is antigenically quite different from BA4/5, and the last boosters available in Australia were for the latter,” said Professor Raina MacIntyre, Biosafety Program Manager at the Kirby Institute. “These don’t provide adequate protection against EG.5.1, but the XBB subvariant boosters that are made by most companies will protect against EG.5.1.”
“In May of this year, the WHO recommended the provision of monovalent XBB boosters. The US anticipates these boosters will be available in September. Haven’t heard an announcement on availability in Australia but hope to think about it.”
An analysis by researchers at the Kirby Institute found that while every available vaccine offers significant protection against COVID-19, variant-specific vaccines (such as the monovalent XBB vaccine) generate 1.6 times better immunity on average.
Pfizer has not applied to the Therapeutic Goods Administration to import its XBB vaccines into Australia. The TGA noted that Pfizer had applied to the FDA and the European Medicines Agency for approval of its monovalent XBB vaccine and said it would welcome a similar application.
Moderna’s bivalent BA.1 vaccine, one of the vaccines available in Australia, generates half the antibody response against Eris compared to “the kraken” XBB.1.5, said the institute’s associate professor Stuart Turville. “But overall there is still good coverage and real efficacy” achieved by existing bivalent vaccines against the new strain, he said.
Despite the spike protein optimization, Eris is similar to the XBB variants that dominated the winter COVID wave, so the population may have increased natural immunity to Eris. The next wave is expected in late spring as natural immunity wanes.
But the resistance of the population from one variant to the next is increasing. Turville said there was a 16-fold drop in antibody levels that could respond to the new variant between Delta and Omicron. Now the antibody levels between the variants only drop about threefold.
“From an immunological point of view, it’s a positive signal,” Turville said. “If you get a booster now, you’ll get a good response to other dominant variants.”
The length of protection a vaccine offers varies from person to person. Experts strongly advise a booster shot, especially if you have not received a newer bivalent vaccine.
“The immunity to Omicron provides some protection against it [Eris] and reduce the severity of the disease,” said Professor Cassandra Berry, immunology expert at Monash University. “It’s important that people stay up to date on their vaccination boosters as the risk of contracting the disease from these pandemic viruses is not over yet.”
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