Fig. 3: Estimated risk (mean hazard ratios with 95% CIs) of Omicron reinfections in different waves by time from most recent vaccination.

n = 42,582, 83,382, 164,263, and 184,566 adults who were at risk of BA.1, BA.2, BA.4/5, and BQ.1/CH.1.1/XBB.1.5 reinfections were included in the models, respectively. Time from most recent vaccination was a time-updated covariate split into 14–90 days, 90–180 days, >180 days. >180 days was used as reference category. Bivalent vaccines were only used from September 2022 onwards, and therefore would only have been relevant to infections in the final wave. The 95% CIs are calculated by estimates ± 1.96 × standard error of the estimates. Adjusted (Supplementary Table 3) for time-fixed covariates age, sex, ethnicity, reporting working in healthcare, reporting having a long-term health condition, deprivation percentile, infection variant, region, number of previous infections, symptoms in most recent infection, whether any previous infection had Ct < 30 or was LFD positive; and time-updated time from most recent infection (Fig. 2) and background infection prevalence. Results remain similar in sensitivity analyses without adjustment for background infection prevalence (Supplementary Table 4).