Table 4.
Vaccine effectiveness for booster COVID-19 vaccine series against infections, hospitalisations, and mortality
| Baseline days (7–28) |
Follow-up days |
I2 | σ | |||
|---|---|---|---|---|---|---|
| 84–111 | 112–139 | |||||
| Any variant | ||||||
| Documented infections | 70% (95% CI 56 to 80; 95% PI −24 to 93) | 56%* (95% CI 35 to 70; 95% PI −48 to 90) | 43%* (95% CI 14 to 62; 95% PI −61 to 87) | 23, 77 | 0·35, 0·63 | |
| κ | 13 (28) | 11 (23) | 8 (16) | .. | .. | |
| Hospitalisations | 89%† (95% CI 82 to 93; 95% PI 59 to 97) | 74%* (95% CI 60 to 83; 95% PI 8 to 93) | 71%* (95% CI 51 to 83; 95% PI −6 to 92) | 34, 64 | 0·35, 0·47 | |
| κ | 7 (11) | 8 (15) | 4 (5) | .. | .. | |
| Omicron | ||||||
| Documented infections | 67% (95% CI 53 to 77; 95% PI −16 to 91) | 51%* (95% CI 30 to 66; 95% PI −44 to 87) | 40%* (95% CI 11 to 59; 95% PI −55 to 84) | 32, 68 | 0·35, 0·51 | |
| κ | 11 (24) | 9 (19) | 7 (14) | .. | .. | |
| Hospitalisations | 89%† (95% CI 82 to 93; 95% PI 59 to 97) | 74%* (95% CI 60 to 83; 95% PI 8 to 93) | 71%* (95% CI 51 to 83; 95% PI −6 to 92) | 30, 68 | 0·32, 0·48 | |
| κ | 7 (11) | 8 (13) | 4 (5) | .. | .. | |
I2 is Higgin's and Thompson's I2 presented at the within-study and between-study levels. σ is the estimate of τ, the SD of effect sizes in the population, presented at the within-study and between-study levels. κ=number of studies pooled (number of cohorts or observations pooled). PI=prediction interval.
*
Vaccine effectiveness at this follow-up timepoint is statistically different from the vaccine effectiveness observed at baseline 2 (14–28 days).
†
Vaccine effectiveness at this follow-up timepoint is statistically different from the vaccine effectiveness observed at baseline 1 (0–13 days).