Mean per cent of population vaccinated during the 2009 H1N1 influenza pandemic
| Epidemic Preparedness Index cluster | Countries with data (n) | Mean per cent of population vaccinated (range) | Difference from cluster 1 Mean (p value*) |
| 1 | 24 | 19.53 (0.60–60.00) | – |
| 2 | 17 | 9.35 (0.43–46.00) | 10.18 (0.007) |
| 3 | 15 | 9.19 (2.00–27.00) | 10.34 (0.008) |
| 4 | 21 | 6.94 (0.96–17.00) | 12.59 (0.0005) |
| 5 | 9 | 4.55 (0.34–10.27) | 14.98 (0.001) |
*Based on a linear regression model predicting a country’s per cent of population vaccinated as a function of Epidemic Preparedness Index (EPI) cluster compared with the best performing EPI cluster.