Immune response against SARS-CoV-2 of primary healthcare personnel in a commune of Santiago, Chile: follow-up at 6 months

Background The COVID-19 pandemic that emerged in Wuhan, China at the end of 2019, spread rapidly around the world with almost 600 million cases and 6.3 million deaths today. The most affected were health workers with at least three times the risk of contracting the disease than the general community. Most studies on seroprevalence in health workers focus on hospital care establishments and what happens in Primary Health Care (PHC) has not been investigated with the same intensity. Objectives to determine the prevalence and know the variation of antibody titers for SARS-CoV-2 in serial samples of primary healthcare personnel from the commune of La Pintana. Method an analytical observational study with a cross-sectional and a longitudinal component, carried out from November 2020 to June 2021. The first component consisted of an IgG antibody seroprevalence study performed at baseline (time 0) in volunteer of a universe of 900 workers. The longitudinal component considered the monitoring of IgG antibodies in those who presented a positive result at baseline and the analysis of neutralizing antibodies in a random sub-sample of 50% of them. Additionally, sociodemographic and clinical information was collected via a questionnaire. Univariate, bivariate, and longitudinal analyses were performed to evaluate differences in antibodies. The study was approved by the Universidad del Desarrollo’s Scientific Ethics Committee. Results 463 primary healthcare workers participated, mostly women and with a median of 38 years; doctors and nurses represented 9.5% each and 14.7% had a history of COVID-19. The seroprevalence at baseline was 22.3% and was associated with younger age, being a doctor and having been in close contact of a case. IgG titers increased with the vaccine, but decreased over time. At the 6-month follow-up, 76% had neutralizing antibodies. Those belonging to indigenous peoples had higher IgG levels and higher rates of neutralizing antibodies. Conclusion Healthcare workers were highly affected by COVID-19, and the medical profession and younger age were factors associated with increased risk. Antibodies decrease over time, highlighting the importance of follow-up studies, as well as the importance of vaccination boosters in healthcare workers, especially those in PHC. Financing This project was funded by the Universidad del Desarrollo, COVID19-UDD 2020-21 Funds. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This project was funded by the Universidad del Desarrollo, COVID19-UDD 2020-21 Funds. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the Scientific Ethics Committee of the Universidad del Desarrollo. Participation was voluntary, the process of signing informed consent was conducted, indicating the scope of the study. There were no associated risks or costs for the participants, and as a benefit, the subjects obtained results on their levels of IgG antibodies against SARS-CoV-2. The result of the blood sample was reported in a maximum of 14 working days to each participant. Data privacy was safeguarded at all times using encrypted information that could only be accessed by researchers, under security standards with a personal and non-transferable key. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present work are contained in the manuscript