Strong Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibody Response of Previously Infected Healthcare Workers Given 1 Dose of mRNA Vaccine

Recent reports indicate that anti–coronavirus disease 2019 (COVID-19) vaccination reduces symptomatic and asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. However, there is little published information on the relative strengths of the neutralizing antibody responses conferred by vaccination and a natural infection or on the benefit of vaccinating a previously infected person. This is particularly important since there are still ongoing studies on the persistence of neutralizing antibodies after a first infection.We followed up 195 healthcare workers (HCWs) who tested positive with a quantitative enzyme-linked immunosorbent assay (Wantai Biological Pharmacy Enterprise Co, Ltd, China) after the first epidemic wave (10 June 2020–10 July 2020). Their neutralizing antibody titers were determined using a virus neutralization assay. About one-fifth (40, 20.5%) of them were vaccinated after January 2021, and 30 (15.4%) were given a single dose of the Pfizer...