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Social Distancing, Mask Use and the Transmission of SARS-CoV-2: A Population-Based Case-Control Study

26 Pages Posted: 8 Dec 2020

See all articles by Marcelo Rodrigues Gonçalves

Marcelo Rodrigues Gonçalves

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul

Rodrigo Citton Padilha dos Reis

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul

Rodrigo Pedroso Tólio

Universidade Federal do Rio Grande do Sul (UFRGS) - Postgraduate Program in Epidemiology

Lucia Campos Pellanda

Universidade Federal de Ciências da Saúde de Porto Alegre

Maria Inês Schmidt

Federal University of Rio Grande do Sul (UFRGS/PPGA)

Natan Katz

Social Medicine Department, Universidade Federal do Rio Grande do Sul

Sotero Serrate Mengue

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul

Pedro C. Hallal

Federal University of Pelotas (UFPel) - Postgraduate Program in Epidemiology

Bernardo Lessa Horta

Federal University of Pelotas (UFPel) - Postgraduate Program in Epidemiology

Mariangela Freitas Silveira

Federal University of Pelotas (UFPel) - Postgraduate Program in Epidemiology

Roberto Nunes Umpierre

Hospital de Clínicas de Porto Alegre

Cynthia Goulart Bastos-Molina

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul

Rodolfo Souza da Silva

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul

Bruce Bartholow Duncan

Federal University of Rio Grande do Sul (UFRGS/PPGA) - Federal University of Rio Grande do Sul

More...

Abstract

Background: Ecologic studies support non-pharmacologic measures to protect against SARS-CoV-2, but few studies have evaluated their effects at the individual level in the community. We aimed to assess the magnitude of the associations of social distancing and mask use with laboratory-confirmed infection by SARS-CoV-2 in adults living in Porto Alegre, Brazil, a city with 1,483,771 inhabitants.

Methods: We conducted a population-based case-control study from late April to June 2020. Cases came from a list of all cases mandatorily notified to municipal authorities; controls were antibody-negative participants of three representative household surveys conducted at the same time-period.

Findings: In logistic regression analyses of 271 cases and 1396 controls adjusted for age, sex, race, educational attainment, income, household size and pandemic moment, those reporting moderate to greatest adherence to social distancing  had between 59% (OR=0·41; 95%CI 0·24-0·70) and 75% (OR=0·25; 0·15-0·42) lower odds of becoming infected, compared to those reporting very little adherence.  Lesser out-of-household exposure reduced odds between 52% (OR=0·48; 0·29-0·77) and 75% (OR=0·25; 0·18-0·36), compared to going out every day all day. In a subsample of controls with data on mask use and cases of equivalent pandemic moment (198 cases and 420 controls), mask use reduced odds of infection by 87% (OR=0·13; 0·04-0·36).

Interpretation: Greater social distancing and always using masks while away from home provided major protection against SARS-CoV-2. These simple measures can be of great benefit during the upcoming phases of the pandemic.

Funding: IATS/FAPERGS, UNIMED Porto Alegre, Instituto Cultural Floresta, Instituto Serrapilheira, Ministry of Health.

Declaration of Interests: The authors have no conflicts of interest to declare.

Ethics Approval Statement: The ethics committee of the Hospital de Clínicas de Porto Alegre approved our study (No. 31499420·5·0000·5327) and the Brazilian National Ethics Committee (No. 30415520·2·0000·5313) approved the accompanying seroprevalence surveys. All participants gave prior informed consent, in written form by the controls and verbally for cases.

Keywords: COVID-19, Communicable Disease Control, Masks, Pandemics, Social Distance, Social Isolation

Suggested Citation

Gonçalves, Marcelo Rodrigues and dos Reis, Rodrigo Citton Padilha and Tólio, Rodrigo Pedroso and Pellanda, Lucia Campos and Schmidt, Maria Inês and Katz, Natan and Mengue, Sotero Serrate and Hallal, Pedro C. and Lessa Horta, Bernardo and Silveira, Mariangela Freitas and Umpierre, Roberto Nunes and Bastos-Molina, Cynthia Goulart and da Silva, Rodolfo Souza and Duncan, Bruce Bartholow, Social Distancing, Mask Use and the Transmission of SARS-CoV-2: A Population-Based Case-Control Study. Available at SSRN: https://ssrn.com/abstract=3731445 or http://dx.doi.org/10.2139/ssrn.3731445

Marcelo Rodrigues Gonçalves

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul ( email )

Rodrigo Citton Padilha Dos Reis

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul ( email )

Rodrigo Pedroso Tólio

Universidade Federal do Rio Grande do Sul (UFRGS) - Postgraduate Program in Epidemiology ( email )

2400, Ramiro Barcelos
2º Andar
Porto Alegre, RS 90035-003
Brazil
+5551984199797 (Phone)

Lucia Campos Pellanda

Universidade Federal de Ciências da Saúde de Porto Alegre ( email )

Maria Inês Schmidt

Federal University of Rio Grande do Sul (UFRGS/PPGA) ( email )

Rua Washington Luiz, 855. Centro
Porto Alegre - RS, 90010-460
Brazil

Natan Katz

Social Medicine Department, Universidade Federal do Rio Grande do Sul ( email )

Sotero Serrate Mengue

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul ( email )

Pedro C. Hallal

Federal University of Pelotas (UFPel) - Postgraduate Program in Epidemiology

Brazil

Bernardo Lessa Horta

Federal University of Pelotas (UFPel) - Postgraduate Program in Epidemiology ( email )

Rua Marechal Deodoro, 1160 - 3° Piso
Pelotas
Brazil

Mariangela Freitas Silveira

Federal University of Pelotas (UFPel) - Postgraduate Program in Epidemiology

Brazil

Roberto Nunes Umpierre

Hospital de Clínicas de Porto Alegre ( email )

Cynthia Goulart Bastos-Molina

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul ( email )

Rodolfo Souza Da Silva

Postgraduate Program in Epidemiology, Universidade Federal do Rio Grande do Sul ( email )

Bruce Bartholow Duncan (Contact Author)

Federal University of Rio Grande do Sul (UFRGS/PPGA) - Federal University of Rio Grande do Sul

Brazil

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