Table 1.
Effectiveness of a single dose and two doses of SARS-CoV-2 vaccines
| No. cohorts | Vaccine effectiveness (%) (95% CI) | I2 (%) | P value for heterogeneity | P value for subgroup differences | Weight (%) | |
|---|---|---|---|---|---|---|
| The first dose | ||||||
| Prevention of SARS-CoV-2 infection | ||||||
| Overall | 44 | 41 (28–54) | 99.6 | < 0.001 | < 0.001 | 100 |
| < 7 days after the first dose | 3 | 1 (− 25–27) | 84.0 | 0.002 | 6.92 | |
| < 14 days after the first dose | 4 | 12 (0–24) | 0.0 | 0.759 | 6.78 | |
| ≥ 7 days after the first dose | 5 | 17 (− 20–55) | 95.3 | < 0.001 | 10.61 | |
| ≥ 14 days after the first dose | 20 | 48 (31–66) | 99.4 | < 0.001 | 46.63 | |
| ≥ 21 days after the first dose | 8 | 56 (42–70) | 92.6 | < 0.001 | 19.45 | |
| 1 dose | 3 | 32 (9–54) | 83.4 | 0.002 | 7.11 | |
| ≥ 1 dose | 1 | 95 (94–96) | .. | .. | 2.50 | |
| Prevention of symptomatic COVID-19 | ||||||
| Overall | 14 | 52 (31–73) | 99.2 | < 0.001 | < 0.001 | 100 |
| < 7 days after the first dose | 1 | 19 (0–45) | .. | .. | 6.79 | |
| ≥ 7 days after the first dose | 2 | 45 (− 43–100) | 99.8 | < 0.001 | 14.63 | |
| ≥ 14 days after the first dose | 5 | 53 (43–62) | 64.2 | 0.025 | 35.24 | |
| ≥ 21 days after the first dose | 2 | 63 (7–100) | 99.1 | < 0.001 | 14.56 | |
| 1 dose | 3 | 44 (14–74) | 94.4 | < 0.001 | 21.43 | |
| ≥ 1 dose | 1 | 95 (92–97) | .. | .. | 7.34 | |
| Prevention of COVID-19 hospital admissions | ||||||
| Overall | 8 | 66 (50–81) | 98.5 | < 0.001 | 0.005 | 100 |
| < 7 days after the first dose | 1 | 74 (71–77) | .. | .. | 13.47 | |
| ≥ 7 days after the first dose | 1 | 61 (47–75) | .. | .. | 12.27 | |
| ≥ 14 days after the first dose | 5 | 61 (41–81) | 97.9 | < 0.001 | 60.93 | |
| ≥ 21 days after the first dose | 1 | 82 (77–88) | .. | .. | 13.33 | |
| Prevention of COVID-19 ICU admissions | ||||||
| Overall | 3 | 45 (42–49) | 39.5 | 0.192 | .. | 100 |
| ≥ 14 days after the first dose | 3 | 45 (42–49) | 39.5 | 0.192 | 100 | |
| Prevention of COVID-19-related death | ||||||
| Overall | 4 | 53 (15–91) | 98.9 | < 0.001 | < 0.001 | 100 |
| ≥ 14 days after the first dose | 3 | 44 (23–64) | 58.1 | 0.092 | 70.60 | |
| ≥ 1 dose | 1 | 97 (91–99) | .. | .. | 29.40 | |
| The second dose | ||||||
| Prevention of SARS-CoV-2 infection | ||||||
| Overall | 34 | 85 (81–89) | 99.5 | < 0.001 | < 0.001 | 100 |
| < 7 days after the second dose | 3 | 75 (51–99) | 95.7 | < 0.001 | 8.72 | |
| < 14 days after the second dose | 2 | 70 (49–91) | 70.8 | 0.064 | 4.77 | |
| ≥ 7 days after the second dose | 14 | 91 (88–93) | 76.5 | < 0.001 | 42.72 | |
| ≥ 14 days after the second dose | 13 | 81 (71–92) | 99.8 | < 0.001 | 37.35 | |
| ≥ 21 days after the second dose | 1 | 94 (78–98) | .. | .. | 2.91 | |
| 2 doses | 1 | 98 (96–99) | .. | .. | 3.52 | |
| Prevention of symptomatic COVID-19 | ||||||
| Overall | 17 | 97 (97–98) | 83.6 | < 0.001 | 0.008 | 100 |
| < 7 days after the second dose | 1 | 100 (94–100) | .. | .. | 5.53 | |
| < 14 days after the second dose | 2 | 75 (59–92) | 46.5 | 0.171 | 0.47 | |
| ≥ 7 days after the second dose | 5 | 97 (96–98) | 17.4 | 0.304 | 32.25 | |
| ≥ 14 days after the second dose | 7 | 96 (94–98) | 87.9 | < 0.001 | 46.53 | |
| ≥ 21 days after the second dose | 1 | 99 (94–100) | .. | .. | 5.67 | |
| 2 doses | 1 | 99 (96–100) | .. | .. | 9.54 | |
| Prevention of COVID-19 hospital admissions | ||||||
| Overall | 8 | 93 (89–96) | 99.0 | < 0.001 | 0.991 | 100 |
| ≥ 7 days after the second dose | 3 | 93 (84–100) | 72.5 | 0.026 | 35.70 | |
| ≥ 14 days after the second dose | 5 | 93 (85–100) | 99.4 | < 0.001 | 64.3 | |
| Prevention of COVID-19 ICU admissions | ||||||
| Overall | 8 | 96 (93–98) | 96.4 | < 0.001 | 0.414 | 100 |
| ≥ 7 days after the second dose | 4 | 97 (93–100) | 18.2 | 0.300 | 38.11 | |
| ≥ 14 days after the second dose | 4 | 94 (87–100) | 98.4 | < 0.001 | 61.89 | |
| Prevention of COVID-19-related death | ||||||
| Overall | 8 | 95 (92–98) | 96.3 | < 0.001 | 0.851 | 100 |
| < 14 days after the second dose | 1 | 96 (83–99) | .. | .. | 8.68 | |
| ≥ 7 days after the second dose | 3 | 97 (95–98) | 11.7 | 0.322 | 37.91 | |
| ≥ 14 days after the second dose | 3 | 93 (82–100) | 98.9 | < 0.001 | 42.36 | |
| 2 doses | 1 | 98 (87–100) | .. | .. | 11.06 | |
CI confidence interval, SARS-CoV-2 severe acute respiratory syndrome coronavirus 2, COVID-19 coronavirus disease 2019