HealthDay News — For health care workers who received a priming dose of the Ad26.COV2.S vaccine, Ad26.COV2.S and mRNA boosters are immunogenic, with the strongest responses after boosting with an mRNA-based vaccine, according to a study published online Jan. 19 in the New England Journal of Medicine.
Roos S.G. Sablerolles, M.D., from the Erasmus University Medical Center in Rotterdam, Netherlands, and colleagues conducted a single-blind, multicenter, randomized, controlled trial involving health care workers who received a priming dose of the Ad26.COV2.S vaccine. Immunogenicity and reactogenicity were assessed 28 days after receipt of no booster, an Ad26.COV2.S booster, an mRNA-1273 booster, or a BNT162b2 booster.
The researchers found that compared with a single Ad26.COV2.S vaccination, homologous or heterologous booster vaccination in 434 participants yielded higher levels of S-specific binding antibodies, neutralizing antibodies, and T-cell responses. Compared with the homologous booster, heterologous regimens that included mRNA-based vaccines resulted in a significantly larger increase in binding antibodies. The most immunogenic was the mRNA-1273 booster, which was associated with higher reactogenicity than the BNT162b2 and Ad26.COV2.S boosters. In the first 2 days after booster administration, local and systemic reactions were generally mild to moderate.
“Single-shot Ad26.COV2.S vaccination adequately primes the immune system,” the authors write. “We found that in the face of waning immunity and circulation of severe acute respiratory syndrome coronavirus 2 variants, these responses were boosted most efficiently with mRNA-based vaccines.”