Participant Characteristics
Of 3,500 participants screened, 3,287 were eligible, and 3,220 adults were enrolled in the study. The participants had a median age of 71 years (interquartile range [IQR] 68-76) and 1,324 (41%) were male (Table 1). The proportion of cohort participants that were vaccinated for influenza was 52% (1,666/3,220) in 2015 and 48% (1,498/3,123) in 2016. In total, 313 (9.7%) had one or more underlying cardiopulmonary condition, most commonly COPD (131; 41.2%), asthma (73; 23.3%), or chronic bronchitis (68; 21.7%) (Table 2). The participants with cardiopulmonary conditions were more likely to be older, male, have more other co-morbidities, and have a higher number of hospital visits than those without cardiopulmonary conditions (Table 1).
The participants were followed-up for a total 316,690 person-weeks (29,005 person-weeks for participants with cardiopulmonary conditions and 287,685 person-weeks for participants without cardiopulmonary conditions). During the two-year follow-up, two participants withdrew and 200 (6.2%) died. Overall, 2365 ARI/SARI episodes (2296 ARI and 69 SARI) were reported in the cohort of which 2362 (99.8%) respiratory swabs were collected (1969 nasal self-swabs and 393 nasopharyngeal swabs by research nurses).