Immunogenicity and reactogenicity of vaccine boosters after Ad26.COV2.S priming

Sablerolles, R.S.G.; Rietdijk, W.J.R.; Goorhuis, A.; Postma, D.F.; Visser, L.G.; Geers, D.; Schmitz, K.S.; Garrido, H.M.G.; Koopmans, M.P.G.; Dalm, V.A.S.H.; Kootstra, N.A.; Huckriede, A.L.W.; Lafeber, M.; Baarle, D. van; GeurtsvanKessel, C.H.; Vries, R.D. de; Kuy, P.H.M. van der; SWITCH Res Grp

doi:doi:10.1056/NEJMoa2116747

BACKGROUND The Ad26.COV2.S vaccine, which was approved as a single-shot immunization regimen, has been shown to be effective against severe coronavirus disease 2019. However, this vaccine induces lower severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein (S)-specific antibody levels than those induced by messenger RNA (mRNA)-based vaccines. The immunogenicity and reactogenicity of a homologous or heterologous booster in persons who have received an Ad26. COV2.S priming dose are unclear.METHODSIn this single-blind, multicenter, randomized, controlled trial involving health care workers who had received a priming dose of Ad26.COV2.S vaccine, we assessed immunogenicity and reactogenicity 28 days after a homologous or heterologous booster vaccination. The participants were assigned to receive no booster, an Ad26. COV2.S booster, an mRNA-1273 booster, or a BNT162b2 booster. The primary end point was the level of S-specific binding antibodies, and the secondary...Show moreBACKGROUND The Ad26.COV2.S vaccine, which was approved as a single-shot immunization regimen, has been shown to be effective against severe coronavirus disease 2019. However, this vaccine induces lower severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein (S)-specific antibody levels than those induced by messenger RNA (mRNA)-based vaccines. The immunogenicity and reactogenicity of a homologous or heterologous booster in persons who have received an Ad26. COV2.S priming dose are unclear.METHODSIn this single-blind, multicenter, randomized, controlled trial involving health care workers who had received a priming dose of Ad26.COV2.S vaccine, we assessed immunogenicity and reactogenicity 28 days after a homologous or heterologous booster vaccination. The participants were assigned to receive no booster, an Ad26. COV2.S booster, an mRNA-1273 booster, or a BNT162b2 booster. The primary end point was the level of S-specific binding antibodies, and the secondary end points were the levels of neutralizing antibodies, S-specific T-cell responses, and reactogenicity. A post hoc analysis was performed to compare mRNA-1273 boosting with BNT162b2 boosting.RESULTSHomologous or heterologous booster vaccination in 434 participants resulted in higher levels of S-specific binding antibodies, neutralizing antibodies, and T-cell responses than a single Ad26.COV2.S vaccination. The increase in binding antibodies was significantly larger with heterologous regimens that included mRNA-based vaccines than with the homologous booster. The mRNA-1273 booster was most immunogenic and was associated with higher reactogenicity than the BNT162b2 and Ad26.COV2.S boosters. Local and systemic reactions were generally mild to moderate in the first 2 days after booster administration.CONCLUSIONSThe Ad26.COV2.S and mRNA boosters had an acceptable safety profile and were immunogenic in health care workers who had received a priming dose of Ad26. COV2.S vaccine. The strongest responses occurred after boosting with mRNA-based vaccines. Boosting with any available vaccine was better than not boosting.Show less

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Immunogenicity and reactogenicity of vaccine boosters after Ad26.COV2.S priming