A single dose of the SARS-CoV-2 vaccine BNT162b2 elicits Fc-mediated antibody effector functions and T-cell responses

While the standard regimen of the BNT162b2 mRNA vaccine for SARS-CoV-2 includes two doses administered three 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 naïve 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.
Graphical Abstract
Tauzin, Nayrac et al., characterize humoral and cellular responses three weeks after a single dose of mRNA BNT162b2 vaccine. They show, in SARS-CoV-2 naïve individuals, that the antibodies elicited have weak neutralizing activity but potent Fc-mediated effector functions and, in SARS-CoV-2 previously infected individuals, that all responses are significantly boosted.