Non-woven masks and SARS-CoV-2 infection in a cluster setting in Japan

Evidence about which types of mask are effective in preventing infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is limited. We examined which mask types were effective against SARS-CoV-2 infection in a cluster setting in Japan. We retrospectively reviewed data from a cluster of COVID-19 cases that occurred at a manufacturing company in mid-August 2021. We included a total of 87 individuals who reported the type of mask worn. We dichotomized the types of mask into non-woven masks or other types of mask, such as cloth or urethane masks. We then examined the associations between the mask type and SARS-CoV-2 infection using logistic regression analysis, adjusting for potential confounders. Participants who wore non-woven masks were less likely to be infected with SARS-CoV-2 (9.7%) compared with those who wore other types of mask (26.7%). After adjusting for potential confounders, wearing a non-woven mask was significantly associated with a reduced risk of infection compared with wearing other mask types (odds ratio = 0.10, 95% confidence interval: 0.01 to 0.80). Non-woven masks were found to be more effective in preventing SARS-CoV-2 infection in a cluster setting than other types of mask, such as cloth or urethane masks.