ABSTRACT
ObjectivesTo estimate the prevalence, incidence, and longevity of antibodies against SARS-CoV-2 among primary healthcare providers (PHCPs). DesignProspective cohort study with 12 months of follow-up. SettingPrimary care in Belgium ParticipantsAny 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 3,648 eligible PHCPs from 2,001 GP practices registered for this study (3,044 and 604 to start in December 2020 and January 2021, respectively). 3,390 PHCPs (92,9%) participated in their first testing timepoint (2,820 and 565, respectively) and 2,557 PHCPs (70,1%) in the last testing timepoint (December 2021). InterventionsParticipants were asked to perform a rapid serological test (RST) targeting IgM and IgG against the receptor binding domain (RBD) of SARS-CoV-2 and to complete an online questionnaire at each of maximum 8 testing timepoints. Primary and secondary outcome measuresThe prevalence, incidence, and longevity of antibodies against SARS-CoV-2 both after natural infection and after vaccination. ResultsAmong 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 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. ConclusionsThis 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. RegistrationTrial registration number: NCT04779424 Strengths and limitations of this studyO_LIThis large cohort study with 12 months follow-up could provide precise estimates of the prevalence and incidence of antibodies against SARS-CoV-2 among primary health care providers (PHCPs) at national and regional level in Belgium. C_LIO_LIThe rapid serological test (RST) used targets IgM and IgG against the receptor binding domain of SARS-CoV-2 and could therefore also assess the antibody response after vaccination, and longevity of antibodies against SARS-CoV-2 both after natural infection and after vaccination, but cannot distinguish between both. C_LIO_LIThe results in PHCPs could be compared to that of the general population and other population groups, e.g. health care workers in hospitals and nursing homes. C_LIO_LIThe use of a convenience sample, missing data points and reduced RST accuracy when performed and interpreted by many different participants could limit the validity of the study results. C_LI
ABSTRACT
IntroductionNational severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence data provides essential information about population exposure to the virus and helps predict the future course of the epidemic. Early cohort studies have suggested declines in levels of antibodies in individuals, associated with, for example, illness severity, age and co-morbidities. This protocol focuses on the seroprevalence among primary health care providers (PHCPs) in Belgium. They manage the vast majority of COVID-19 patients in addition to other patients and therefore play an essential role in the efficient organisation of health care. Currently, evidence is lacking on 1. how many PHCPs get infected with SARS-CoV-2 in Belgium, 2. the rate at which this happens, 3. their clinical spectrum, 4. their risk factors, 5. the effectiveness of the measures to prevent infection and 6. the accuracy of the serology-based point-of-care test in a primary care setting. Methods and analysisThis study will be set up as a prospective cohort study. General practitioners (GPs) and other PHCPs (working in a GP practice) will be recruited via professional networks and professional media outlets to register online to participate. Registered GPs and other PHCPs will be asked at each testing point (n=9) to perform a capillary blood sample antibody point-of-care test (OrientGene(R)) and complete an online questionnaire. The primary outcomes are the prevalence and incidence of antibodies against SARS-CoV-2 in PHCPs during a 12-month follow-up period. Secondary outcomes include the longevity of antibodies against SARS-CoV-2. Ethics and disseminationEthical approval has been granted by the Ethics Committee of the University Hospital Antwerp/University of Antwerp (Belgian registration number: 3002020000237). Alongside journal publications, dissemination activities include the publication of monthly reports to be shared with the participants and the general population through the publicly available website of the Belgian health authorities (Sciensano). RegistrationTrial registration number: NCT04779424 Article summaryO_ST_ABSStrengths and limitations of this studyC_ST_ABSO_LIThis large cohort study will provide regular, timely and precise data at national level on prevalence and incidence of antibodies against SARS-CoV-2 among primary health care providers (PHCPs) managing the vast majority of COVID-19 and other patients and therefore essential to organise health care efficiently. C_LIO_LIThis study will familiarise PHCPs with the use of serology-based point-of-care tests (POCTs) and validate the POCT in a primary care setting. C_LIO_LIMissing data points and the use of a convenience sample could limit the validity of the study results. C_LI
