SARS-CoV-2 antibodies persist up to 12 months after natural infection in healthy employees working in non-medical contact-intensive professions

Int J Infect Dis. 2023 Jan:126:155-163. doi: 10.1016/j.ijid.2022.11.025. Epub 2022 Nov 24.


Objectives: This study aimed to evaluate dynamics of antibody levels after exposure to SARS-CoV-2 for 12 months in Dutch non-vaccinated hairdressers and hospitality staff.

Methods: In this prospective cohort study, blood samples were collected every 3 months for 1 year and analyzed using a qualitative total antibody enzyme-linked immunosorbent assay (ELISA) and a quantitative immunoglobulin (Ig)G antibody ELISA. Participants completed 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 (β) and 95% confidence intervals (CIs) 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 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 for up to 12 months in all participants. Older age (β, 10-years increment: 24.6, 95% CI: 5.7-43.5) and higher body mass index (β, 5kg/m² increment: 40.0, 95% CI: 2.9-77.2) were significantly associated with a higher peak of antibody levels.

Conclusion: In this cohort, SARS-CoV-2 antibodies persisted for up to 1 year after initial seropositivity, suggesting long-term natural immunity.

Keywords: COVID-19 serological testing; Cohort study; Contact profession; Immunoglobulin G; Natural infection; SARS-CoV-2 antibodies.

MeSH terms

  • Antibodies, Viral
  • COVID-19*
  • Humans
  • Immunoglobulin G
  • Prospective Studies
  • SARS-CoV-2*


  • Antibodies, Viral
  • Immunoglobulin G