ABSTRACT
OBJECTIVE: To evaluate dynamics of antibody levels following exposure to SARS-CoV-2 during 12 months in Dutch non-vaccinated hairdressers and hospitality staff. METHODS: In this prospective cohort study, blood samples were collected every three months for one year, and analyzed using a qualitative total antibody ELISA and a quantitative IgG antibody ELISA. Participants filled out questionnaires, providing information on demographics, health and work. Differences in antibody levels were evaluated using Mann-Whitney U and Wilcoxon Signed Rank tests. Beta coefficients (B) and 95% confidence intervals (95%CI) were calculated using linear regression. RESULTS: Ninety-five of 497 participants (19.1%) had ≥1 seropositive measurement before their last visit using the qualitative ELISA. Only 2.1% (2/95) seroreverted during follow-up. Of the 95 participants, 82 (86.3%) tested IgG seropositive in the quantitative ELISA too. IgG antibody levels significantly decreased in the first months (p<0.01), but remained detectable up to 12 months in all participants. Higher age (B, 10-years increment: 24.6, 95%CI: 5.7-43.5) and higher BMI (B, 5kg/m² increment: 40.0, 95%CI: 2.9-77.2) were significantly associated with a higher peak of antibody levels. CONCLUSIONS: In this cohort, SARS-CoV-2 antibodies persisted for up to one year after initial seropositivity, suggesting long-term natural immunity.