Longevity of SARS-CoV-2 Antibody in Health Care Workers: 6-Months Follow Up

The prevalence and longevity of acquired immunity to coronavirus disease 2019 (COVID-19) in health care workers (HCWs) is of great interest, especially with the roll-out of vaccines for SARS-CoV-2. Determining such immunity may enhance knowledge about susceptibility of HCWs to COVID-19, frequency of vaccine administration, and degree of workplace risk, and may also support enactment of better workplace policies and procedures. The present study reports on 6-months follow-up serosurveillance to determine the longevity of SARS-CoV-2 antibodies in HCWs. Sub-sample (n=35) of the original serosurveillance in HCWs (n = 3,458) with baseline, 8-week, and 6-month blood sampling were analyzed. Information on job duties, location, COVID-19 symptoms, polymerase chain reaction test history, travel since January 2020, and household contacts with COVID-19 was collected. Of 35 subjects, 13 were seropositive at baseline and maintained positivity at 8-week follow-up, with 3 losing positivity at 6-month follow-up. Among 22 subjects who were seronegative at baseline and seropositive at 8-week follow-up, all but one maintained positivity at 6-month follow-up. There was no significant effect of all factors (e.g., age, gender, job duties) examined at the .05 level on seropositivity at 6-month follow-up. The observed antibody longevity was 7.0+/-0.6 months for seropositive subjects (n=13), and 4.5+/-0.8 months for those seronegative subjects (n=22), at baseline. The longest duration of seropositivity observed in this cohort was 7.9 months (236 days). With reported COVID-19-related symptoms up to 4.7 months prior to baseline blood sampling, possibly longer antibody presence is suggested. Similarly, seropositivity at 6-month follow-up further suggests greater antibody longevity than observed in this study.