1. Ad26 vaccine vector immunity: much noise, little signal — and that’s good news In this industry-sponsored pooled analysis by van Rosmalen and colleagues (Johnson & Johnson, Leiden/Beerse), the authors systematically evaluated the real-world relevance of pre-existing and vaccine-induced adenovirus serotype 26 (Ad26) neutralizing antibodies (NAbs) on the immunogenicity of Ad26-vectored vaccines across 21 clinical studies comprising 3,851 participants from 15 countries. Ad26 NAb seroprevalence varied markedly by geography: 78% in Africa (ranging from 65% in Côte d’Ivoire to 94% in Tanzania), 41% in Thailand, 15% in the United States, and 12% in Europe. Despite this wide variation, the impact of naturally occurring Ad26 NAbs on immune responses to Ad26-based Ebola (Ad26.ZEBOV/MVA-BN-Filo, n=395) and HIV (Ad26.Mos4.HIV, n=194) vaccine regimens was inconsistent and clinically negligible: in Africa, median EBOV glycoprotein ELISA peak responses were 5,131 EU/mL in baseline Ad26-seronegative versus 4,967 EU/mL in seropositive participants. Critically, in a separate analysis comparing 348...
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