Prevalence of SARS-CoV-2 antibodies among Belgian nursing home residents and staff during the primary COVID-19 vaccination campaign

Abstract

Background

Nursing home residents (NHR) and staff have been disproportionally affected by the COVID-19 pandemic and were therefore prioritised in the COVID-19 vaccination strategy. However, frail older adults, like NHR, are known to have decreased antibody responses upon vaccination targeting other viral antigens.

Objectives

As real-world data on vaccine responsiveness, we assessed the prevalence of SARS-CoV-2 antibodies among Belgian NHR and staff during the primary COVID-19 vaccination campaign.

Methods

In total, we tested 1629 NHR and 1356 staff across 69 Belgian NHs for the presence of SARS-CoV-2 IgM/IgG antibodies using rapid tests. We collected socio-demographic and COVID-19-related medical data through questionnaires. Sampling occurred between 1 February and 24 March 2021, in a randomly sampled population that received none, one or two BNT162b2 vaccine doses.

Results

We found that during the primary vaccination campaign with 59% of the study population fully vaccinated, 74% had SARS-CoV-2 antibodies. Among fully vaccinated individuals only, fewer residents tested positive for SARS-CoV-2 antibodies (77%) than staff (98%), suggesting an impaired vaccine-induced antibody response in the elderly, with lowest seroprevalences observed among infection naïve residents. COVID-19 vaccination status and previous SARS-CoV-2 infection were predictors for SARS-CoV-2 seropositivity. Alternatively, age ≥ 80 years old, the presence of comorbidities and high care dependency predicted SARS-CoV-2 seronegativity in NHR.

Conclusion

These findings highlight the need for further monitoring of SARS-CoV-2 immunity upon vaccination in the elderly population, as their impaired humoral responses could imply insufficient protection against COVID-19.

Trial registration

This study was retrospectively registered on ClinicalTrials.gov (NCT04738695).

Keywords:

• SARS-CoV-2 seroprevalence
• nursing homes
• nursing home residents
• COVID-19 vaccination
• vaccination campaign

Acknowledgements

The SCOPE study team would like to thank all participating nursing homes, staff members and residents. Additionally, we thank the general practitioner trainees and (nursing) students for contributing to the sampling. Lastly, we thank the Belgian Institute for Public Health, Sciensano, for funding this research.

Author contributions

Conceptualisation, S.H., A.D.S., E.DG., P.C., J.V., B.S.; data analysis, E.DR.; data interpretation; S.H., A.D.S., E.DG., P.C., J.V., B.S, E.M., E.DR.; funding acquisition, S.H., A.D.S., P.C.; project administration, E.M., L.D.R, T.D., M.D., P.V.N, S.D., A.C., N.D.C.; sample collection, L.D.R, T.D., M.D., P.V.N, S.D., A.C., N.D.C, E.M.; draft, E.M.; L.D.R.; review and editing, S.H, A.D.S, E.DG., P.C., J.V., B.S., E.DR., L.D.R, T.D., M.D., P.V.N, S.D., A.C., N.D.C., S.C., L.B. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets supporting the conclusions of this article are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by the Belgian Institute for Health, Sciensano (SC_045).