Table 2.
Pooled Adjusted VE for All Patients (Irrespective of Age)
| Influenza Types and Subtypes Analyzed Subgroups | No. of Studies | Pooled VE Across All Seasons (95% CI) | I 2 Statistic, % | Publication Bias, Egger’s Test P Value |
|---|---|---|---|---|
| H1N1 | ||||
| Vaccination status: medical records | 24 | 52 (45–58) | 32.7 | .031 |
| Vaccination status: self-reported | 6 | 62 (46–73) | 55.0 | N/A |
| Respiratory specimen swab: ≤7 d | 39 | 54 (49–58) | 39.5 | .022 |
| Respiratory specimen swab: ≤4 d | 7 | 59 (47–69) | 0.0 | N/A |
| Adjusted age | 26 | 57 (51–63) | 32.1 | .034 |
| Adjusted age & medical conditions | 20 | 53 (46–59) | 43.6 | .148 |
| H3N2 | ||||
| Vaccination status: medical records | 26 | 25 (15–34) | 55.0 | .988 |
| Vaccination status: self-reported | 5 | 32 (-0–53) | 76.9 | N/A |
| Respiratory specimen swab: ≤7 d | 35 | 28 (22–34) | 57.5 | .301 |
| Respiratory specimen swab: ≤4 d | 8 | 18 (-26–47) | 63.3 | N/A |
| Adjusted age | 23 | 34 (28–40) | 11.5 | .794 |
| Adjusted age & medical conditions | 20 | 21 (10–30) | 70.5 | .997 |
| Influenza B | ||||
| Vaccination status: medical records | 26 | 43 (31–52) | 70.3 | .701 |
| Vaccination status: self-reported | 5 | 48 (36–59) | 28.2 | N/A |
| Respiratory specimen swab: ≤7 d | 33 | 48 (43–53) | 28.2 | .974 |
| Respiratory specimen swab: ≤4 d | 10 | 38 (4–60) | 77.5 | .070 |
| Adjusted age | 22 | 50 (44–56) | 26.5 | .893 |
| Adjusted age & medical conditions | 21 | 40 (27–51) | 70.7 | .252 |
| All influenza | ||||
| Vaccination status: medical records | 39 | 43 (35–49) | 75.3 | .807 |
| Vaccination status: self-reported | 7 | 48 (31–61) | 84.5 | N/A |
| Respiratory specimen swab: ≤7 d | 56 | 46 (41–51) | 70.6 | .152 |
| Respiratory specimen swab: ≤4 d | 12 | 38 (15–55) | 77.3 | .009 |
| Adjusted age | 32 | 47 (42–52) | 56.5 | .477 |
| Adjusted age & medical conditions | 37 | 43 (34–51) | 79.8 | .184 |
Abbreviations: CI, confidence interval; N/A, not applicable; VE, vaccine effectiveness.