Table 2 Grading of experimental, observational, and modelling studies according to the quality of evidence they provide to support causal associations between immunisation and its proposed benefits
From: The broader economic impact of vaccination: reviewing and appraising the strength of evidence
Quality of evidence | Experimental studies | Observational studies | Modelling studies or conjecture |
|---|---|---|---|
High | Randomised trials | Double-upgraded analytical observational studies | Â |
Moderate | Downgraded randomized trials | Upgraded analytical observational studies | Â |
Low | Double-downgraded randomized trials | Analytical observational studies | Â |
Very low | Triple-downgraded randomized trials | Case series and case reports | Modelling studies or conjecture |