The use of face masks at home by infected individuals reduced the transmission of SARS-CoV-2 to their household contacts

The use of face masks at home by a person diagnosed with COVID-19 significantly reduced transmission of the virus to their household contacts. This is the result of research led in Lleida by the Lleida Biomedical Research Institute (IRBLleida) and the University of Lleida (UdL), with the participation of staff from the Biomedical Research Network Centre for Epidemiology and Public Health (CIBERESP), the Institute of Public Health of Navarra and the Public Health Agency of Catalonia, among others. The research, which was carried out between May 2022 and February 2024 in a context in which the Omicron variant of the virus was circulating, has been published in the journal Epidemiology & Infection.

SARS-CoV-2 transmission within households accounted for a significant proportion of community infections. For this reason, non-pharmacological measures, such as the use of face masks, were key to reducing infections. The research team analysed 203 index cases (positive individuals) and 230 cohabiting contacts to understand how mask use affected the risk of transmission within the home. The results show that when the infected person wore a mask, the incidence of infection among their contacts was 36%, compared to 56% in cases where they did not wear a mask. In statistical terms, this represents a 69% reduction in the risk of transmission.

'The use of masks as a means of containment (i.e., by the infected person) appears to be much more effective than as protection for healthy individuals once the infection is known,' explained IRBLleida researcher Pere Godoy. The results suggest that public health protocols and recommendations from primary care centres could reinforce the recommendation to wear masks at home in the event of a positive case, as well as the vaccination of close contacts and cohabitants. 'The study provides evidence that reinforces the importance of simple but effective measures in domestic settings, especially during episodes of high transmission,' added the researcher.

This project was made possible thanks to funding from the Carlos III Health Institute and the Biomedical Research Network Centre for Epidemiology and Public Health (CIBERESP).

Article: Godoy P, Pardos J, García Cenoz M, et al. Mask wearing by COVID-19 index cases reduces SARS-CoV-2 transmission to household contacts. Epidemiology and Infection. 2025;153:e125. doi:10.1017/S0950268825100642.