Designing effectiveness and impact studies for respiratory syncytial virus immunisation in low- and middle-income countries

Respiratory syncytial virus (RSV) is a leading cause of childhood pneumonia and 97 % of the estimated 100,000 annual deaths globally, occur in low and middle-income countries (LMICs). An increasing number of immunisation strategies are being developed. However, there is increasing awareness that much of the evidence of the efficacy and effectiveness of RSV immunisations is derived from high-income countries, while results may not accurately extrapolate to LMICs. There is thus an urgent need for carefully planned post-licensure studies that are appropriate to the widely differing conditions in LMICs. We outline immunisation evaluation study designs with scenario-based options for evaluating RSV immunisations in LMICs and summarize high-level recommendations for their use. The case-control test-negative study design is likely to be most suited to estimate immunisation effectiveness in LMIC settings and a pre-vs-post immunisation study design will allow a measure of immunisation impact following the introduction of RSV immunisation.