The new bivalent (two-strain) Moderna COVID-19 vaccine booster triggered stronger neutralizing antibody responses against the highly transmissible Omicron variant at 28 days than the previously authorized booster, with no safety concerns, according to the interim results of a phase 2/3 open-label, nonrandomized study published late last week in the New England Journal of Medicine."These findings indicate that bivalent vaccines may be a new tool in the response to emerging variants," the researchers wrote.The US Centers for Disease Control and Prevention recommended Moderna's bivalent booster for adults on Sep 1, shortly after the Food and Drug Administration approved it, in addition to Pfizer's bivalent version, which is approved for people 12 years and older.New version versus oldA team led by Moderna scientists evaluated immune response and safety of the updated booster against Omicron (mRNA-1273.214), its subvariants, and previous variants with that of the older Moderna booster (monovalent vaccine; mRNA-1273) against the wild-type virus in 814 participants from Feb 18 to Mar 23, 2022.
The bivalent booster was designed to target both the wild-type and Omicron viral strains. Participants, who had received the older booster at least 3 months before, were given either a dose of the bivalent (437 patients) or monovalent (377) vaccine as a second booster.
Median time between the first and second boosters was similar for both vaccine types, at about 135 days.Average participant age was 57.3 years in the bivalent group and 57.5 years in the monovalent group, and 59.0% and 50.7% were women, respectively.