Bivalent COVID-19 booster vaccines remained effective this winter despite the emergence of new omicron subvariants that they weren’t designed to target, a new study from North Carolina has found.
To provide updated protection to recipients, two bivalent boosters were authorized in August 2022. Each, from drugmakers Moderna and Pfizer, contained equal amounts of spike messenger RNA from the ancestral SARS-CoV-2 subvariants and of the BA.4–BA.5 subvariants that had become predominant.
In the current study, investigators used data from September 2022 to February 2023 to determine if these bivalent shots continued to remain protective against BQ.1–BQ.1.1 and XBB–XBB.1.5, subvariants that had subsequently edged out BA.4–BA.5. Data represented all bivalent booster-vaccinated North Carolina residents aged 12 years and older.
In people who had previously been vaccinated or boosted, each of the authorized bivalent shots were associated with added protection against omicron infection or severe infection, the researchers found. Efficacy was highest against hospitalization and death when compared with infection.
Waning efficacy
Protection waned gradually over time, investigators added. Effectiveness against hospitalization or death reached 67% after 2 weeks, falling to 38% after 20 weeks.
The XBB.1.5 subvariant is still very much in play. As of April 8, it accounted for 90% of SARS-CoV-2 infections, according to the Centers for Disease Control and Prevention.
The study results were published in an editorial in the New England Journal of Medicine.
Related articles:
LTC residents mount immune fight after bivalent booster shot, study shows
FDA expected to OK second omicron booster for seniors soon
FDA authorizes omicron-targeting vaccines as preferred COVID booster shots
