TY - JOUR T1 - Prevalence, incidence and longevity of antibodies against SARS-CoV-2 among primary healthcare providers in Belgium: a prospective cohort study with 12 months of follow-up. JF - BMJ Open Y1 - 2022 A1 - Niels Adriaenssens ED - Beatrice Scholtes ED - Pauline Van Ngoc ED - Laƫtitia Buret KW - Adult KW - Belgium KW - COVID-19 KW - Female KW - Follow-Up Studies KW - Health Personnel KW - Humans KW - Immunoglobulin G KW - Immunoglobulin M KW - incidence KW - Male KW - prevalence KW - Prospective Studies KW - SARS-CoV-2 KW - Seroepidemiologic Studies AB -

OBJECTIVES: To estimate the prevalence, incidence and longevity of antibodies against SARS-CoV-2 among primary healthcare providers (PHCPs).

DESIGN: Prospective cohort study with 12 months of follow-up.

SETTING: Primary care in Belgium.

PARTICIPANTS: Any general practitioner (GP) working in primary care in Belgium and any other PHCP from the same GP practice who physically manages (examines, tests, treats) patients were eligible. A convenience sample of 3648 eligible PHCPs from 2001 GP practices registered for this study (3044 and 604 to start in December 2020 and January 2021, respectively). 3390 PHCPs (92,9%) participated in their first testing time point (2820 and 565, respectively) and 2557 PHCPs (70,1%) in the last testing time point (December 2021).

INTERVENTIONS: Participants were asked to perform a rapid serological test targeting IgM and IgG against the receptor binding domain of SARS-CoV-2 and to complete an online questionnaire at each of maximum eight testing time points.

PRIMARY AND SECONDARY OUTCOME MEASURES: The prevalence, incidence and longevity of antibodies against SARS-CoV-2 both after natural infection and after vaccination.

RESULTS: Among all participants, 67% were women and 77% GPs. Median age was 43 years. The seroprevalence in December 2020 (before vaccination availability) was 15.1% (95% CI 13.5% to 16.6%), increased to 84.2% (95% CI 82.9% to 85.5%) in March 2021 (after vaccination availability) and reached 93.9% (95% CI 92.9% to 94.9%) in December 2021 (during booster vaccination availability and fourth (delta variant dominant) COVID-19 wave). Among not (yet) vaccinated participants the first monthly incidence of antibodies against SARS-CoV-2 was estimated to be 2.91% (95% CI 1.80% to 4.01%). The longevity of antibodies is higher in PHCPs with self-reported COVID-19 infection.

CONCLUSIONS: This study confirms that occupational health measures provided sufficient protection when managing patients. High uptake of vaccination resulted in high seroprevalence of SARS-CoV-2 antibodies in PHCPs in Belgium. Longevity of antibodies was supported by booster vaccination and virus circulation.

TRIAL REGISTRATION NUMBER: NCT04779424.

VL - 12 CP - 9 M3 - 10.1136/bmjopen-2022-065897 ER -