Protection of Healthcare Workers Against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Reinfection

To the Editor—Recent reports of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection have raised questions as to whether and to what degree a first infection protects against reinfection [1, 2]. This is particularly important for healthcare workers (HCW) as they are always on the front line combating both the present epidemic and any new waves of SARS-CoV-2 infection. These workers can also transmit the virus to coworkers and hospitalized susceptible patients. In their recent study, Lumley et al [3] presented 6 months of data from a longitudinal seroprevalence study of UK HCW and showed that SARS-CoV-2 anti-nucleocapsid antibodies wane within months. We screened 8758 French HCW for total serum SARS-CoV-2 anti-spike antibodies between 10 June and 10 July 2020, after the first epidemic wave, and the end of first lockdown using a quantitative enzyme-linked immunosorbent assay (ELISA) (Wantai Biological Pharmacy Enterprise Co, Ltd, China). Their neutralizing antibody titers were determined with a virus neutralization assay [4]. The incidence of SARS-CoV-2 during the second epidemic wave was determined with a nucleic-acid amplification method on nasopharyngeal swab sample [5] taken from all symptomatic individuals and those who had been in contact with a symptomatic individual. All ELISA-positive personnel identified by the first serologic screening were retested from 30 November to 9 December to determine the evolution of SARS-CoV-2 antibodies. This study was approved by the French Research Ethics Committee Est-III (COVID BioToul, ID-RCB 2020-A01292-37, ClinicalTrials.gov dentifier: NCT04385108). After a median follow-up of 167 days (interquartile range [IQR], 156–172), there were 1028 new infections (12.1%) among the 8482 seronegative HCW and 5 reinfections (1.8%) among the 276 seropositive HCW (P < .01, χ 2 test). The 5 reinfected people (Table 1) included 2 with very low or undetectable titers of neutralizing antibodies after the first infection and 3 with above-median titers (median 16). Three reinfected subjects were symptomatic, but only one had a significantly increased (>4-fold) neutralizing antibody titer. The other 2 reinfections were asymptomatic with no significant change in neutralizing antibodies (Table 1). Overall, the neutralizing antibody titers of the 276 seropositive HCW increased significantly between June/July (median: 16) and November/December (median: 32, P < .01; Wilcoxon signed rank test). The increases in neutralizing antibody in the HCW who developed SARS-CoV-2 antibodies after an asymptomatic infection were similar to those who developed symptomatic infections (P = .43, Wilcoxon test). Similarly, the ELISA indexes of the 276 seropositive HCW increased significantly between June/July (median: 41.2) and November/December (median: 97.6, P < .01; Wilcoxon signed rank). Clinical Characteristics of the 5 SARS-CoV-2 Reinfections Abbreviations: ELISA, enzyme-linked immunosorbent assay; HCW, healthcare worker; S/CO, sample/cutoff. aFever, rhinorrhea, cough, dyspnea, chest pain, intestinal disturbances, dysgueusia, anosmia, headache, asthenia, myalgia; not hospitalized. bAnosmia; not hospitalized. cFever, rhinorrhea, dyspnea, chest pain, dysgueusia, anosmia, asthenia, myalgia, eye pain, pharyngitis; not hospitalized. dFever, cough, dyspnea, chest pain, headache, asthenia, myalgia, pharyngitis; not hospitalized. eCough, headache; not hospitalized. Clinical Characteristics of the 5 SARS-CoV-2 Reinfections Abbreviations: ELISA, enzyme-linked immunosorbent assay; HCW, healthcare worker; S/CO, sample/cutoff. aFever, rhinorrhea, cough, dyspnea, chest pain, intestinal disturbances, dysgueusia, anosmia, headache, asthenia, myalgia; not hospitalized. bAnosmia; not hospitalized. cFever, rhinorrhea, dyspnea, chest pain, dysgueusia, anosmia, asthenia, myalgia, eye pain, pharyngitis; not hospitalized. dFever, cough, dyspnea, chest pain, headache, asthenia, myalgia, pharyngitis; not hospitalized. eCough, headache; not hospitalized. The absence of decrease in neutralizing antibodies following SARS-CoV-2 infections, contrary to what have been previously reported [6], could be due to recall responses during the second epidemic wave. Our data indicate that an initial SARS-CoV-2 infection protected HCW against reinfection for at least 167 days. However, a protective neutralizing antibody level could not be determined. These findings could be used to compare the immunity developed after a natural infection with that conferred by current SARS-CoV-2 vaccines. Acknowledgments. The English text was edited by Dr Owen Parkes. We thank the CRB TBR, the Clinical Research Center 1436 and the Delegation for clinical research and innovation of the Toulouse University Hospital for their highly valuable implication. Potential conflicts of interest. All authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.