Impact of Preexisting Anti–Adenovirus 26 Humoral Immunity on Immunogenicity of the Ad26.COV2.S Coronavirus Disease 2019 Vaccine
Mathieu Le Gars, Jerald Sadoff, Frank Struyf, Dirk Heerwegh, Carla Truyers, Jenny Hendriks, Glenda Gray, Beatriz Grinsztejn, Paul Goepfert, Hanneke Schuitemaker, Macaya Douoguih
Abstract
This secondary analysis of the phase 3 ENSEMBLE trial (NCT04505722) assessed the impact of preexisting humoral immunity to adenovirus 26 (Ad26) on the immunogenicity of Ad26.COV2.S-elicited severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody levels in 380 participants in Brazil, South Africa, and the United States. Among those vaccinated in Brazil and South Africa, 31% and 66%, respectively, had prevaccination serum-neutralizing activity against Ad26, with little preexisting immunity detected in the United States. Vaccine recipients in each country had similar postvaccination spike (S) protein-binding antibody levels, indicating that baseline immunity to Ad26 has no clear impact on vaccine-induced immune responses.