Table 4
Meta-analysis according to subgroups for alpha variant.
| Subgroup | SI |
Heterogeneity |
Egger’s test |
||||
|---|---|---|---|---|---|---|---|
| N | Mean | 95% CI | I 2 | Cochran’s Q | p-value | ||
| All estimates | 75 | 5.17 | 4.87 | 5.47 | 97.10 | 2026* | 0.58 |
| SI re-estimated: | |||||||
| No | 61 | 5.11 | 4.80 | 5.43 | 97.27 | 1910* | 0.46 |
| Yes | 14 | 5.41 | 4.57 | 6.25 | 91.24 | 110* | 0.93 |
| Country: | |||||||
| China | 30 | 5.59 | 5.16 | 6.02 | 91.24 | 250.5* | 0.07 |
| Others | 45 | 4.88 | 4.49 | 5.27 | 97.77 | 1765* | 0.21 |
| Distribution$: | |||||||
| Gamma | 32 | 5.60 | 5.20 | 6.00 | 94.74 | 345* | 0.51 |
| Normal | 17 | 5.24 | 4.60 | 5.88 | 95.13 | 245* | 0.87 |
| Lognormal | 11 | 4.46 | 3.69 | 5.24 | 91.43 | 150* | 0.14 |
| Weibull | 8 | 5.45 | 4.74 | 6.15 | 87.84 | 65.76* | 0.05 |
| SI estimated with negative values: | |||||||
| Yes | 30 | 4.93 | 4.53 | 5.32 | 96.69 | 552* | 0.15 |
| No | 28 | 5.61 | 5.01 | 6.21 | 94.36 | 363* | 0.14 |
| NA | 17 | 4.98 | 4.41 | 5.55 | 94.86 | 344* | 0.0015 |
| Measures of control implemented: | |||||||
| Yes | 42 | 5.26 | 4.87 | 5.65 | 97.43 | 875* | 0.56 |
| No | 6 | 4.67 | 3.75 | 5.58 | 73.20 | 16.85† | 0.63 |
| NA | 26 | 5.00 | 4.49 | 5.52 | 94.97 | 687* | 0.0112 |
*P-value < 0.001, †p-value < 0.005, $Statistical distribution was not available or not clear for seven studies. SI: Serial interval; N: Number; 95% CI: 95% confidence interval; I2: I-square or index of heterogeneity statistic; Cochran’s Q: Cochran’s Q heterogeneity statistic; Egger: Egger’s test for publication bias; NA: Not available.