| Outcome | Studies contributing data | Estimated effect (95% CI) |
| Influenza‐like illness | Potter 1997; Hayward 2006; Lemaitre 2009 | OR 0.71 (0.58 to 0.88) |
| GP consultations for ILI | Hayward 2006 | OR 0.48 (0.33 to 0.69) |
| Deaths from ILI | Hayward 2006 | OR 0.72 (0.31 to 1.70) |
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