(HealthDay News) — Interim results of an ongoing study show that use of the bivalent omicron-containing vaccine mRNA-1273.214 as a second booster elicits neutralizing antibody responses against omicron that are superior to those for mRNA-1273, according to a study published in the The New England Journal of Medicine.

Spyros Chalkias, MD, from Moderna in Cambridge, Massachusetts, and colleagues compared the 50-μg bivalent vaccine mRNA-1273.214 (25 μg each of ancestral Wuhan-Hu-1 and omicron B.1.1.529 [BA.1] spike messenger RNAs) with the previously authorized 50-μg mRNA-1273 booster in an ongoing phase 2/3 study.

Either mRNA-1273.214 or mRNA-1273 was administered as a booster to adults who had previously received a 2-dose primary series and first booster dose of mRNA-1273 three or more months earlier (437 and 377 participants, respectively).

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The researchers found that, for participants with no previous SARS-CoV-2 infection, the geometric mean titers of neutralizing antibodies against the omicron BA.1 variant were 2372.4 after receipt of the mRNA-1273.214 booster and 1473.5 after the mRNA-1273 booster.

In addition, the mRNA-1273.214 and mRNA-1273 boosters elicited geometric mean titers of 727.4 and 492.1, respectively, against omicron BA.4/5. Higher binding antibody responses against multiple other variants was elicited by the mRNA-1273.214 booster vs the mRNA-1273 booster. The 2 boosters had similar safety and reactogenicity.

“These results are consistent with the evaluation of our bivalent beta-containing vaccine, which induced enhanced and durable antibody responses,” the authors wrote. “Together, these findings indicate that bivalent vaccines may be a new tool in the response to emerging variants.”

Several authors disclosed financial ties to pharmaceutical companies, including Moderna, which funded the study.

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