• Alexandra Tauzin, Manon Nayrac, Mehdi Benlarbi, Shang Yu Gong, Romain Gasser, Guillaume Beaudoin-Bussières, Nathalie Brassard, Annemarie Laumaea, Dani Vézina, Jérémie Prévost, Sai Priya Anand, Catherine Bourassa, Gabrielle Gendron-Lepage, Halima Medjahed, Guillaume Goyette, Julia Niessl, Olivier Tastet, Laurie Gokool, Chantal Morrisseau, Pascale Arlotto, Leonidas Stamatatos, Andrew T McGuire, Catherine Larochelle, Pradeep Uchil, Maolin Lu, Walther Mothes, Gaston De Serres, Sandrine Moreira, Michel Roger, Jonathan Richard, Valérie Martel-Laferrière, Ralf Duerr, Cécile Tremblay, Daniel E Kaufmann, and Andrés Finzi.
• Centre de Recherche du CHUM, Montréal, QC H2X 0A9, Canada; Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montreal, QC H2X 0A9, Canada.
• Cell Host Microbe. 2021 Jul 14; 29 (7): 1137-1150.e6.

AbstractWhile the standard regimen of the BNT162b2 mRNA vaccine for SARS-CoV-2 includes two doses administered 3 weeks apart, some public health authorities are spacing these doses, raising concerns about efficacy. However, data indicate that a single dose can be up to 90% effective starting 14 days post-administration. To assess the mechanisms contributing to protection, we analyzed humoral and T cell responses three weeks after a single BNT162b2 dose. We observed weak neutralizing activity elicited in SARS-CoV-2 naive individuals but strong anti-receptor binding domain and spike antibodies with Fc-mediated effector functions and cellular CD4+ T cell responses. In previously infected individuals, a single dose boosted all humoral and T cell responses, with strong correlations between T helper and antibody immunity. Our results highlight the potential role of Fc-mediated effector functions and T cell responses in vaccine efficacy. They also provide support for spacing doses to vaccinate more individuals in conditions of vaccine scarcity.Copyright © 2021 Elsevier Inc. All rights reserved.

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