Observational study: prospective longitudinal cohort (Green)
Whether or not persons who have already been infected SARS-CoV-2 should be vaccinated is unclear. In this observational cohort study, the authors enrolled 100 health care workers, including 38 with a documented history of SARS-CoV-2 infection (mean duration between infection and vaccination, 111 days). The mean age of these previously infected participants was 35.1 years (95% confidence interval [CI], 31.7 to 38.6). 62 participants (25 men and 37 women) who had not been previously infected were also included. Both groups of participants received the messenger RNA vaccine BNT162b2 (Pfizer–BioNTech). The most remarkable finding of this study was the significantly lower neutralizing antibody titer after administration of a second dose of vaccine in previously uninfected patients than the titer after only a single dose of vaccine in previously infected participants. The authors concluded that these findings provide evidence that after the administration of a single dose of vaccine, the humoral response against SARS-CoV-2 in persons with a history of SARS-CoV-2 infection is greater than the response in previously uninfected participants who have received a second dose.
Anichini G, Terrosi C, Gandolfo C, Gori Savellini G, Fabrizi S, Miceli GB, Cusi MG. SARS-CoV-2 Antibody Response in Persons with Past Natural Infection. N Engl J Med. 2021 Apr 14. doi: 10.1056/NEJMc2103825.