Risk factors for SARS-Cov-2 infection at a United Kingdom electricity-generating company: a test-negative design case-control study

Objectives Identify workplace risk factors for SARS-Cov-2 infection, using data collected by a United Kingdom electricity-generating company. Methods Using a test-negative design case-control study we estimated the odds ratios (OR) of infection by job category, site, test reason, sex, vaccination status, vulnerability, site outage, and site COVID-19 weekly risk rating, adjusting for age, test date and test type. Results From an original 80,077 COVID-19 tests, there were 70,646 included in the final analysis. Most exclusions were due to being visitor tests (5,030) or tests after an individual first tested positive (2,968). Women were less likely to test positive than men (OR=0.71; 95% confidence interval=0.58-0.86). Test reason was strongly associated with positivity and although not a cause of infection itself, due to differing test regimes by area it was a strong confounder for other variables. Compared to routine tests, tests due to symptoms were highest risk (94.99; 78.29-115.24), followed by close contacts (16.73; 13.80-20.29) and looser work contacts 2.66 (1.99-3.56). After adjustment, we found little difference in risk by job category, but some differences by site with three sites showing substantially lower risks, and one site showing higher risks in the final model. Conclusions Infection risk was not associated with job category. Vulnerable individuals were at slightly lower risk, tests during outages were higher risk, vaccination showed no evidence of an effect on testing positive, and site COVID-19 risk rating did not show an ordered trend in positivity rates. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by the PROTECT (Partnership for Research in Occupational, Transport and Environmental COVID Transmission) COVID-19 National Core Study on Transmission and Environment and managed by the Health and Safety Executive on behalf of HM Government. ### 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 Observational Research Ethics Committee of the London School of Hygiene and Tropical Medicine gave ethical approval for this work 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, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The data is not available