Are Omicron-specific vaccines any better than original jabs? What early tests show

Early animal studies conducted by scientists across the world have found that Omicron-specific boosters of coronavirus vaccine do no better job than the previously available ones in preventing the infection. The Omicron variant of Covid-19, which is still globally dominant, is the highest transmissible strain so far.

A lot of research has been going on to find out if a third dose of the vaccine is good enough to build immunity against Omicron. Leading vaccine makers Pfizer and Moderna earlier also announced that they have started clinical trials of their Omicron-specific vaccine shots.

“What we’re seeing coming out of these preclinical studies in animal models is that a boost with a variant vaccine doesn’t really do any better than a boost with the current vaccine,” said David Montefiori, director of the Laboratory for AIDS Vaccine Research and Development at Duke University Medical Center in Durham, North Carolina, speaking to Nature journal.

A report in the journal said most of the early studies involved a small batch of animals and all of them hinted that a customised booster shot of the vaccine will not change anything against Omicron. These studies are yet to be peer reviewed.

According to the report, one study examined immune responses of rhesus macaques (a breed of monkeys), just eight primates, with two doses of Moderna’s original vaccine and one booster shot of either the same dose or an Omicron-specific version. Researchers found the monkeys boosted with either vaccine showed a broad antibody response against all variants of concern, including Omicron.

However, the study examined responses up to only four weeks, meaning it is not clear as to how long the efficacy of the vaccine will last.

In another study, scientists examined a ‘replicating RNA’ vaccine in mice. They were given three doses of the replicating RNA vaccine – two doses based on the ancestral SARS-CoV-2 strain followed by a single Omicron-specific booster – made by HDT Bio in Seattle, Washington, the report said.

While the third dose of Omicron-specific vaccine did not provide better results, a response was seen in mice that were administered one dose of the vaccine based on ancestral strain, followed by two doses of the variant-specific vaccine.

“There are important questions that still need to be addressed. Hopefully Pfizer and Moderna’s Omicron studies in humans will do that,” Montefiori told the journal.