Table 3.
Relative effectiveness of booster vaccination versus 2-dose primary series.
| Number of positive SARS-CoV-2 tests |
|||
|---|---|---|---|
| Booster exposure interval (days 14–16 post booster vaccination) | Control interval (days 4–6 post booster vaccination) | Relative effectiveness (95% CI) [reference: control interval]1 | |
| Delta period | 14 | 42 | 70% (42%, 84%) |
| Omicron period | 70 | 141 | 54% (38%, 66%) |
| <65 years old | 39 | 84 | 59% (37%, 73%) |
| ≥65 years old | 31 | 57 | 48% (18%, 67%) |
Delta period: September 23, 2021-November 30, 2021; Omicron period: January 1, 2022- March 19, 2022.
1
Relative effectiveness is the percentage reduction in the odds of testing positive for the booster exposure versus the control interval = ([1-ORodds of SARS-CoV-2 in booster exposure interval vs odds of SARS-CoV-2 in control interval]*100%).