Social, demographic and behavioural determinants of SARS-CoV-2 infection: A case-control study carried out during mass community testing of asymptomatic individuals in South Wales, December 2020

Thomas, D. R.; Fina, L.; Adamson, J.; Sawyer, C.; Jones, A.; Nnoaham, K.; Barrasa, A.; Shankar, G.; Williams, C.

Background Between 21 November and 22 December 2020, a SARS-CoV-2 community testing pilot took place in the South Wales Valleys. Lateral flow tests were offered to all people aged over 10 years living, studying or working in the area. Methods We conducted a case-control study in adults taking part in the pilot using an anonymous online questionnaire. Social, demographic and behavioural factors were compared in people with a positive test (cases) and a sample of negatives (controls). Population attributable fractions (PAF) were calculated for factors with significantly increased odds following multivariate analysis. Results A total of 199 cases and 2,621 controls were recruited by SMS (response rates: 27.1% and 37.6% respectively). Following adjustment, cases were more likely to work in the hospitality sector (aOR: 3.39, 95% CI: 1.43-8.03), social care (aOR: 2.63, 95% CI: 1.22-5.67) or healthcare (aOR: 2.31, 95% CI: 1.29-4.13), live with someone self-isolating due to contact with a case (aOR: 3.07, 95% CI: 2.03-4.62), visit a pub (aOR: 2.87, 95% CI: 1.11-7.37), and smoke or vape (aOR: 1.54, 95% CI: 1.02-2.32). In this community, and at this point in the epidemic, reducing transmission from a household contact who is self-isolating would have the biggest public health impact (PAF: 0.2). Conclusion Infection prevention and control should be strengthened to help reduce household transmission. As restrictions on social mixing are relaxed, hospitality venues will become of greater public health importance, and those working in this sector should be adequately protected. Smoking or vaping may be an important modifiable risk factor.