Table 1 Study periods
Period | Omicron subvariant prevalence [13] | Duration |
|---|---|---|
Period 1 | BA.2 prevalence < 25% (predominant variant: BA.1) | January 1–February 6, 2022 |
Period 2 | BA.2 prevalence ≥ 25% but < 75% | February 7–February 27, 2022 |
Period 3 | BA.2 prevalence ≥ 75% | February 28–May 1, 2022 |
Period 4a | BA.5 prevalence < 25% | May 2–May 31, 2022 |
Period 5 | BA.5 prevalence ≥ 25% but < 75% | June 1–July 3, 2022 |
Period 6 | BA.5 prevalence ≥ 75% | July 4–July 31, 2022 |