The use of public transport and contraction of SARS-CoV-2 in a large prospective cohort in Norway

Background For many people public transport is the only mode of travel, and it can be challenging to keep the necessary distances in such a restricted space. The exact role of public transportation and risk of SARS-CoV-2 transmission is not known. Methods Participants (n = 121,374) were untested adult Norwegian residents recruited through social media who in the spring of 2020 completed a baseline questionnaire on demographics and the use of public transport. Incident cases (n = 1069) had a positive SARS-CoV-2 polymerase chain reaction test registered at the Norwegian Messaging System for Infectious Diseases by January 27, 2021. We investigated the association between the use of public transport and SARS-CoV-2 using logistic regression. Odds ratios (ORs) with 95% confidence intervals (CIs) adjusted for age, calendar time, gender, municipality, smoking, income level, fitness and underlying medical conditions were estimated. Frequency of the use of public transport was reported for 2 week-periods. Results Before lockdown, those who tested positive on SARS-CoV-2 were more likely to have used public transport 1–3 times (OR = 1.28, CI 1.09–1.51), 4–10 times (OR = 1.49, CI 1.26–1.77) and ≥ 11 times (OR = 1.50, CI 1.27–1.78, p for trend < 0.0001) than those who had not tested positive. Conclusion The use of public transport was positively associated with contracting SARS-CoV-2 both before and after lockdown