Antibody Responses after a Single Dose of SARS-CoV-2 mRNA Vaccine

Abstract

Antibody Responses after a Single Dose of SARS-CoV-2 mRNA VaccineTo the Editor: Currently, two vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that involve messenger RNA (mRNA) platform technology have been approved for emergency use by the Food and Drug Administration (FDA) (mRNA-1273, Moderna; and BNT162b2, Pfizer). 1,2Phase 3 trials of these vaccines showed greater than 90% efficacy at preventing symptomatic infection after two doses administered 3 to 4 weeks apart.These trials primarily involved participants without previous SARS-CoV-2 infection.More than 26 million cases of coronavirus disease 2019 (Covid-19) have been documented in the United States, and high rates of seropositivity have been observed in recent studies. 3Thus, the immune response to vaccination in persons with previous SARS-CoV-2 infection needs to be defined.In this study, we determined antibody levels at baseline and 3 weeks after the first dose of the BNT162b2 SARS-CoV-2 mRNA vaccine in 36 health care workers who received laboratory confirmation of SARS-CoV-2 infection 30 to 60 days before they received the vaccine and 152 health care workers without a history of SARS-CoV-2 infection (Table S1 in the Supplementary Appendix, available with the full text of this letter at NEJM.org).The biospecimens from vaccine recipients were obtained in the context of a clinical study at Children's Mercy Kansas City, and their use was reviewed and approved by the Children's Mercy institutional review board.The requirement for written informed consent was waived, given that participants self-enrolled after they had reviewed a study information letter and were given the opportunity to ask questions.Using a multiplex bead-binding assay (Milliplex