Antibody Response to the BNT162b2 mRNA COVID-19 Vaccine in Subjects with Prior SARS-CoV-2 Infection

TLDR

Antibody levels wane after SARS‑CoV‑2 infection, yet immune memory persists for months, implying that naturally infected individuals may mount a faster and more sustained response to COVID‑19 vaccines than naïve persons. The study examined the antibody response dynamics to the BNT162b2 mRNA COVID‑19 vaccine in six previously infected healthcare workers compared with nine infection‑naïve controls. Six previously infected workers and nine uninfected controls received the BNT162b2 vaccine, and antibody titers were measured over time to assess response dynamics. The vaccine was well tolerated, with only increased local pain in previously infected subjects; neutralizing antibody titers rose markedly after vaccination, with a rapid RBD IgG surge one week after the first dose in pre‑immune individuals that matched the titers of naïve subjects after two doses, suggesting a single dose may suffice for those previously infected.

Abstract

Although antibody levels progressively decrease following SARS-CoV-2 infection, the immune memory persists for months. Thus, individuals who naturally contracted SARS-CoV-2 are expected to develop a more rapid and sustained response to COVID-19 vaccines than naïve individuals. In this study, we analyzed the dynamics of the antibody response to the BNT162b2 mRNA COVID-19 vaccine in six healthcare workers who contracted SARS-CoV-2 in March 2020, in comparison to nine control subjects without a previous infection. The vaccine was well tolerated by both groups, with no significant difference in the frequency of vaccine-associated side effects, with the exception of local pain, which was more common in previously infected subjects. Overall, the titers of neutralizing antibodies were markedly higher in response to the vaccine than after natural infection. In all subjects with pre-existing immunity, a rapid increase in anti-spike receptor-binding domain (RBD) IgG antibodies and neutralizing antibody titers was observed one week after the first dose, which seemed to act as a booster. Notably, in previously infected individuals, neutralizing antibody titers 7 days after the first vaccine dose were not significantly different from those observed in naïve subjects 7 days after the second vaccine dose. These results suggest that, in previously infected people, a single dose of the vaccine might be sufficient to induce an effective response.