Moderna begins dosing for Phase 2 testing of omicron-specific COVID-19 vaccine booster

Moderna, Inc. dosed the first participant this week for its Phase 2 study of a COVID-19 booster vaccine tailored to the omicron variant, mRNA-1273.529, kicking off a two cohort trial that will span the United States.

In all, approximately 300 participants will be enrolled in each cohort. One cohort will consist of patients previously issued the two-dose primary series of the mRNA-1273 vaccine at least six months prior. A second cohort will include those who have undertaken both the primary series and a 50 µg booster dose of mRNA-1273, with the latter issued at least three months prior. Both studies will be given a single dose of the omicron-specific booster.

Through the information gathered, researchers will evaluate the immunogenicity, safety, and reactogenicity of the mRNA-1273.529 booster and consider its inclusion in Moderna’s multivalent booster program.

The news comes even as new data, published in the New England Journal of Medicine, showed a 6.3-fold decline in the normal Moderna vaccine’s antibody efficacy against omicron after 29 days. It marked a more rapid decline in titer levels than against the ancestral strain of the virus.

“We are reassured by the antibody persistence against Omicron at six months after the currently authorized 50 µg booster of mRNA-1273,” Stéphane Bancel, CEO of Moderna, said. Despite the reduction in peak titers over time, data showed that antibody levels remained detectable in all participants. “Nonetheless, given the long-term threat demonstrated by Omicron’s immune escape, we are advancing our Omicron-specific variant vaccine booster candidate, and we are pleased to begin this part of our Phase 2 study.”

According to the new data, after seven months post-second dosing, but prior to the third booster, omicron neutralization was detected in only 55 percent of participants. Six months following the third booster dose, there was a 6.3-fold decline from peak titers. Comparatively, over the same period, titers against the original strain of the SARS-CoV-2 virus declined 2.3-fold.

Testing of the new booster will encompass up to 24 sites.