Figure 1.

Stability of hybrid immunity protection against BA.5 infection following infection with BA.1 or BA.2 subvariants

(A) Incidence of documented SARS-CoV-2 infection overlaid with the period of dominance of the BA.1 and BA.2 variants, Jan 1–Apr 14, 2022, divided into 15-day sub-intervals (shades of blue), and the period of dominance of the BA.5 variant, Jun 1–Sep 14, 2022, also divided into 15-day sub-intervals (shades of purple). Two illustrative comparisons are represented. In period d (BA.5 dominance), the risk of infection was compared between individuals with a first documented infection in one of the seven subintervals of BA.1 and BA.2 dominance (A–G), represented with the solid arrow. In the second example with the dashed arrow, in period a of BA.5 dominance, the risk of infection was compared between individuals with a first documented infection in the first four periods of BA.1 and BA.2 dominance (A–D), as reinfections were only considered 90 days following the first infection. (B) RR of reinfection versus first infection in each subinterval of the period of BA.5 dominance (curves a–g, corresponding with the periods of the same letter as in (A) over time since the first infection. The increase in risk is well described by a saturating function (appendix pp 5, 9) as represented by the fitted line (dashed, black). RR=relative risk.