Live-attenuated RSV vaccines are probably effective in young children. This is an important conclusion from Ruth Karron and co-workers after analyzing data from seven previous trials. According to the PATH snapshot of RSV vaccines, there are seven live-attenuated RSV vaccines in phase 1 clinical trials while none have progressed into phase 2. Karron showed that RSV positive respiratory infections requiring medical attention were reduced by 67% after receiving one of the more promising vaccines in this analysis of past phase I clinical trials. The authors combined data from previous live-attenuated vaccine candidates administered intranasally to 241 children aged 6 to 24 months in total. Five of seven vaccines, referred to as “more promising”, induced a ≥4-fold increase of neutralizing antibodies titer in at least 80% of recipients. Antibody titers of vaccinated children increased by more than 14-fold after being later exposed to wild-type RSV, indicating a substantial memory immune response. While, high antibody titers likely reflect a good immune response overall and do not act alone to protect against RSV, one dose might be sufficient to protect infants during RSV season. Based on this study, intranasal live-attenuated vaccines have substantial potential to protects young children after the protection granted by maternal antibodies wears off. It is time for a phase 2 proof-of-concept study demonstrating the full potential of live-attenuated RSV vaccines in young infants.
Full article on PubMed.