Table 4: Body of Evidence Examined According to Study Design*.
| Study Design | Number of Eligible Studies |
|---|---|
| RCT Studies | |
| Systematic review of RCTs | |
| Large RCT | Pneumococcal vaccination 1 |
| Small RCT | Influenza vaccination 1 |
| Observational Studies | |
| Systematic review of non-RCTs with contemporaneous controls | |
| Non-RCT with contemporaneous controls | |
| Systematic review of non-RCTs with historical controls | |
| Non-RCT with historical controls | |
| Database, registry, or cross-sectional study | |
| Case series | |
| Retrospective review, modeling | |
| Studies presented at an international conference or other sources of grey literature | |
| Expert opinion | |
| Total | 2 |
*
Abbreviation: RCT, randomized controlled trial.