Moderna: Omicron booster shows promise
Moderna released preliminary results on Wednesday on an updated coronavirus vaccine targeting the omicron variant, calling it “our lead candidate” to serve as a U.S. booster shot in the fall.
The firm’s researchers tested a booster dose combining the original vaccine with one targeted specifically against omicron, the variant that became dominant last winter. They found that among those with no evidence of prior coronavirus infection, the combination produced 1.75 times the level of neutralizing antibodies against omicron as the existing Moderna vaccine did alone.
While those results seem encouraging on their face, many experts worry that the virus is evolving so fast that it is outpacing the ability to modify vaccines — at least as long as the United States relies on human clinical trials for results.
Moderna’s new findings, from a clinical trial involving 814 volunteers, indicate that the updated vaccine produced a significantly stronger immune response against omicron than the existing vaccine a month after the booster shot was given. The booster shots followed three earlier doses of Moderna’s vaccine.
But omicron has been spawning subvariants for months, and some vaccine experts say what matters now is how well a new booster formulation would protect against the latest subvariants, BA.4 and BA.5, not omicron itself. First detected in South Africa early this year, those two subvariants now account for 13% of new cases in the United States and are spreading fast. By some estimates, within a month they could outcompete the two other omicron subvariants BA.2 and BA.2.12.1, which are dominant now.
Moderna did not release any data on how the updated vaccine worked against BA.4 or BA.5. In a presentation Wednesday morning, Dr. Stephen Hoge, the firm’s president, said researchers were still gathering data on those and other subvariants.
But he said that a very small sample, together with isolated other studies, suggested that the levels of neutralizing antibodies triggered by the updated vaccine were two to threefold lower against the BA.4 and BA.5 subvariants, compared to against omicron.