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New data indicate Moderna’s Covid bivalent booster may be more effective against currently circulating Omicron variants of the virus than its original vaccine, the company said Monday.

Like data released by Pfizer and BioNTech regarding their Covid vaccine, the new data involves lab measurements of antibodies and their ability to neutralize the SARS-CoV-2 virus, not data on how well the vaccines prevent cases of symptomatic illness or severe disease.

Moderna said in a press release that giving its current booster led to an increase in the number of antibodies that neutralize the most common Omicron variants, BA.4 and BA.5, by 15-fold. The data have not been published in a peer-reviewed journal or released in a preprint.


That meant that the geometric mean titers of BA.4/BA.5 antibodies were 5.11-fold higher for those who received the new booster compared to those who received a booster of the original Moderna Covid vaccine if those people had been previously infected with Covid. For those without previous Covid infection, those numbers were 6.29 times higher than with the original vaccine.

One caveat is that with previous studies of experimental Moderna boosters that targeted new strains of the virus, it was possible to compare volunteers who received the original vaccine and the modified one at the same time.


But the new booster, which targets both the original strain of the SARS-CoV-2 virus and the Omicron sub-variants BA.4/BA.5, was authorized by the Food and Drug Administration before such a study was conducted. Jacqueline Miller, a Moderna senior vice president, said that the company did not think it was ethical to enroll a new cohort on the original Moderna booster when the recommendations from the FDA and the Centers for Disease Control and Prevention were that people should get a booster that is more targeted at the BA.4/BA.5 strains.

So far, results have been mixed as to whether the BA.4/BA.5 boosters are more effective against the new strains than the original shots. Studies conducted in the laboratories of the vaccine researcher Daniel Barouch, of Beth Israel Deaconess Medical Center, and the virologist David Ho, of Columbia University, have indicated that the new shots may not be more effective than the original one. But studies conducted at the University of Texas and at Emory University have shown that the new shots may yield better antibody protection.

Miller emphasized that Moderna has used consistent methods for its antibody studies, including for the earlier studies that showed the original vaccine was effective, and that those studies have been greenlit by the FDA.

Eric Topol, director and founder of the Scripps Research Translational Institute, said that he viewed the new results as positive and largely confirmatory of the Emory work. He also praised the study for its relatively large size, involving 511 previously vaccinated volunteers.

“This study is encouraging and suggests that the bivalent boosters provide an added benefit compared to the prior mRNA-1273 booster,” said Mehul Suthar, lead author of the Emory analysis, in an email. “We will need to stay up to date with this bivalent booster to protect against yet another Omicron wave this fall/winter.”

Moderna also said that the new booster appeared to be effective against a new worrisome variant, BQ1.1, in a preliminary study using samples from 40 of the study’s volunteers.

“​​What people have been looking for is an understanding of, ‘if I got this booster what does my protection look like against BQ1.1 or some other variant,’” Miller said. “Ultimately the effectiveness data are the really important data.” She said that Moderna expects data from an ongoing observational study to help answer that question in the first quarter of next year.

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