Estimating risk when zero events have been observed

In principle, we could apply this general approach to situations where we have experienced events but simple formulas such as the Ro3 do not exist and would require computer assistance and substantial statistical knowledge to solve. [...]comparing the risk between interventions that have different numbers of trials and adverse events remains a challenge. A second is, when combining probabilities, the level of pessimism is compounded beyond that specified at the 5% level of the Ro3. [...]using the Ro3 when making comparisons between interventions, decision makers may mix methods resulting in incoherent assessments.