Summary of the number needed to treat (NNT) with the influenza vaccine in different age groups to protect against influenza
| NNT against influenza | Relative risk (95% CI) | |
| Age 3–16 years (LAIV) | 7 | 0.22 (0.11–0.41) |
| Age 2–16 years (IIV) | 5 | 0.36 (0.28–0.48) |
| Healthy adults | 71 | 0.41 (0.36–0.47) |
| Age >65 years | 30 | 0.42 (0.27–0.66) |
Data compiled from Cochrane reviews on influenza vaccination preventing influenza in healthy adults, children and >65-year-olds [33–35]. LAIV: live attenuated influenza vaccine; IIV: inactivated influenza vaccine.