Vaccination status
The vaccination status of all participants is shown in Table 2. A greater proportion of unvaccinated (7.0%) individuals was in the case group than in the control group (4.5%). Among the case group, 2.4% completed a partial vaccination, and 58.7% completed a full vaccination, whereas, among the control group, the corresponding proportions were 1.2% and 53.7%, respectively. A total of 132 (31.9%) individuals had completed a booster vaccination in the case group, and 336 (40.6%) in the control group before the outbreak in April 2022. There was a significant difference in vaccination status between the case and control groups (P = 0.006).