Social Distancing, Mask Use, and Transmission of Severe Acute Respiratory Syndrome Coronavirus 2, Brazil, April–June 2020
Marcelo Rodrigues Gonçalves, Rodrigo Citton Padilha dos Reis, Rodrigo Pedroso Tólio, Lúcia Campos Pellanda, María Inês Schmidt, Natan Katz, Sotero Serrate Mengue, Pedro C. Hallal, Bernardo Lessa Horta, Mariângela Freitas da Silveira, Roberto Nunes Umpierre, Cynthia Goulart Bastos-Molina, Rodolfo Silva, Bruce Bartholow Duncan
Abstract
We assessed the associations of social distancing and mask use with symptomatic, laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection in Porto Alegre, Brazil. We conducted a population-based case-control study during April-June 2020. Municipal authorities furnished case-patients, and controls were taken from representative household surveys. In adjusted logistic regression analyses of 271 case-patients and 1,396 controls, those reporting moderate to greatest adherence to social distancing had 59% (odds ratio [OR] 0.41, 95% CI 0.24-0.70) to 75% (OR 0.25, 95% CI 0.15-0.42) lower odds of infection. Lesser out-of-household exposure (vs. going out every day all day) reduced odds from 52% (OR 0.48, 95% CI 0.29-0.77) to 75% (OR 0.25, 95% CI 0.18-0.36). Mask use reduced odds of infection by 87% (OR 0.13, 95% CI 0.04-0.36). In conclusion, social distancing and mask use while outside the house provided major protection against symptomatic infection.