Table 4. Simplest recommended model for estimating the influenza vaccination effect according to the modifying effect and bias from influenza vaccination history.
| Modifying effect | Bias ± 5% or more | Relevant bias ± 10% or more | Simplest model recommended | |
|---|---|---|---|---|
| All patients | No | Yes | No | Summarised model with one previous seasona,b |
| Primary healthcare patients | Yes | Yes | No | Full model with three previous seasonsc |
| Hospitalised patients | No | Yes | Yes | Summarised model with one previous seasona |
| Age 9–64 years | Yes | No | No | Full model with three previous seasonsc |
| Age ≥ 65 years | No | Yes | Yes | Summarised model with one previous seasona |
| Influenza A(H1N1) | No | Yes | No | Summarised model with one previous seasona,b |
| Influenza A(H3N2) | No | Yes | Yes | Summarised model with one previous seasona |
| Influenza B | Yes | Yes | No | Full model with three previous seasonsc |
a Summarised model categories: current-season vaccination regardless of prior doses, no current-season vaccination but any prior doses and no current-season vaccination or prior doses as reference category.
b If only relevant bias is considered (± 10% or more), the only-current-season model would be sufficient.
c Full model categories: current-season vaccination and three prior doses, current-season vaccination and one to two prior doses, current-season vaccination and no prior doses, no current-season vaccination and three prior doses, no current-season vaccination and one to two prior doses, and no current-season vaccination and no prior doses as reference category.