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Moderna on Tuesday released data supporting its strategy to develop a booster vaccine that combines different versions of the coronavirus, showing that it could slightly increase recipients’ immunity against multiple variants.
A bivalent booster shot that the company began working on in February 2021, tailored to combat the original version of the virus and the beta variant, increased virus-blocking antibody levels against a variety of variants, including Omicron, better than one normal booster vaccination.
The study, released as a preprint prior to peer review, is early proof of concept that the approach could work, but the vaccine formula will likely never be used. Moderna’s lead booster candidate, tuned to block the Omicron variant and original version of the virus, is still in human testing, with results expected by the end of June.
While the bivalent vaccine that was the subject of Tuesday’s report contains four of the mutations found in the Omicron variant, the Omicron bivalent vaccine will contain 32 of those mutations.
External experts noted that the research offers limited insight into future vaccination strategy as this vaccine formulation is unlikely to be used. The beta variant emerged in South Africa in late 2020 and raised alarm for its ability to bypass immunity, but quickly fizzled out. Experts are watching closely how omicron is developing into new sub-variants worldwide.
“At this point, we should at least consider a bivalent Omicron booster,” said David R. Martinez, a viral immunologist at the University of North Carolina’s Gillings School of Global Public Health, in an email. “We should also ask ourselves what the overall goal is, since the variant-specific boosters are a patch-fix approach and the ancestral vaccines in general seem to do a good job of protecting against serious diseases.”
The increase in immune defense was measured in the study in laboratory tests. The two-fold increase in antibodies blocking Omicron “may be statistically significant but is unlikely to be biologically important,” wrote John P. Moore, professor of microbiology and immunology at Weill Cornell Medicine, in an email.
A panel of experts advising the Food and Drug Administration met this month to discuss the possible makeup of a fall booster vaccine, but did not review specific data. The committee is expected to meet again in the coming months to help select the best vaccine for a potential fall booster campaign.
The bivalent beta vaccine appeared to augment immunity and trigger higher antibody levels “even when additional variants of concern were not included in the booster vaccine,” Moderna CEO Stéphane Bancel said in a statement. “We believe that a bivalent booster vaccine, if approved, would create a new tool as we continue to respond to new variants.”
Antibody levels were higher with the bivalent vaccine than with a regular booster dose against a number of variants and remained so after six months, with the exception of the delta variant. The study was not designed to measure the effectiveness of the vaccine.