evidence: In the end-of-follow-up survey, we asked the participants about their face mask use during the study period. Participants reported on face mask use by selecting one of six responses to the question ‘How often over the last 2 weeks have you used a face mask when you have been close to others outside your home?’ (1) Always; (2) Almost always (at least 75% of the time); (3) Often (50–75% of the time); (4) Sometimes (25–50% of the time); (5) A few times (up to 25% of the time); and (6) Never. [...] Data on face mask use were collected in the end-of-follow-up survey; therefore, all participants who did not respond to this survey are excluded from the analysis. We analyse the data using only complete cases as the number of participants who responded to the face mask question and those who did not respond to other survey questions was small (n = 23, 0.7%).