American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Mar 2021
Live-attenuated Vaccines Prevent Respiratory Syncytial Virus-associated Illness in Young Children.
Rationale: Active immunization is needed to protect infants and young children against respiratory syncytial virus (RSV). Rationally designed live-attenuated RSV vaccines are in clinical development. Objectives: Develop preliminary estimates of vaccine efficacy, assess durability of antibody responses to vaccination and "booster" responses after natural RSV infection, and determine sample sizes needed for more precise estimates of vaccine efficacy. ⋯ Rates of RSV-MAARI and RSV-MAALRI in placebo recipients were 21% and 7%, respectively. Given these rates, a study of 540 RSV-naive children would have 90% power to demonstrate ≥55% efficacy against RSV-MAARI and ≥80% efficacy against RSV-MAALRI; if rates were 10% and 3%, a study of 1,300 RSV-naive children would be needed. Conclusions: Rapid development of a live-attenuated RSV vaccine could contribute substantially to reducing the global burden of RSV disease.