Flow chart describing the selection of participants for the analysis.

The number individuals in this figure is not the same as some of the numbers in Table 1 because of issing data in key variables.

Vaccination coverage and cumulative incidence of SARS-CoV-2 reinfection in the study population.

Panel A presents the percentages of the study population vaccinated over time. The cumulative incidence of SARS-CoV-2 reinfections is presented by the number of vaccination doses before (panels) and after (lines) first infection (panels B-C). Shaded regions: 95% CIs. 1V-I, 2V-I represented 1, 2 and 3 vaccine doses before infection, respectively; 1V-I-V, 2V-I-V corresponds to 1 and 2 doses before infection, then post-infection vaccination, respectively. As mentioned in the Results section, 142 and 144 study participants who received one and two pre-infection vaccine doses received two post-infection vaccine doses. We do not show the corresponding plot for those individuals who received 3 pre-infection doses as their post-infection dose was after the start of the follow-up, in December.

Characteristics of the study population and reinfection rate by post-infection vaccination status.

Here, reinfection rate refers to e percentage of the relevant study subpopulation with evidence of reinfection between December 1, 2022 and January 3, 2023. Note that for e variables on region, occupation, and clinical severity, data are missing for large fractions of the study population.

Effect of vaccine dose on SARS-CoV-2 reinfection stratified by pre-infection vaccination.

Error bars (95% CIs) and circles represent aHR for SARS-CoV-2 reinfection estimated using Cox proportional hazards models. 1V-I-V, 2V-I-V, 3V-I-V corresponds to 1, 2 and 3 vaccine doses before infection, then vaccination, respectively; they were compared to 1V-I, 2V-I, 3V-I, respectively. V-I-V, Partial V-I-V, Full V-I-V and Booster V-I-V represent any pre-infection vaccination, partial vaccination, full vaccination and booster vaccination before infection, followed by post-infection vaccination, respectively.

Vaccine-related protection against SARS-CoV-2 reinfection stratified by demographic characteristic.

The vertical dotted line at 1.0 indicates no effect on protection.