Efficacy of anti-RSV vaccination in preventing respiratory syncytial virus disease and severe illness in older adults: a systematic review of randomized controlled trials.

Purpose: Several vaccines against respiratory syncytial virus (RSV) are being developed. The objective of this systematic review is to determine the efficacy of these vaccines in preventing RSV disease in adults over 60 years of age, especially regarding severe illness.

Methods: We researched MEDLINE, CENTRAL, Scopus, medRxiv, bioRxiv and ClinicalTrials.gov until April/2024. Randomized controlled trials studying an anti-RSV vaccine in adults above 60 years and reporting RSV-related acute respiratory infection/disease (ARI/ARD), lower respiratory tract infection/disease (LRTI/LRTD) and severe LRTI/LRTD were included. Vaccine efficacy was calculated as ([1 - risk ratio] × 100). Risk of bias and certainty of evidence were assessed by RoB2 tool and GRADE approach. The meta-analytical relative risk of ARI/ARD and LRTI/LRTD was estimated, with a subgroup analysis performed according to the vaccine type. The random effects model was used.

Results: We included seven studies, five addressing prefusion vaccines and two regarding non-prefusion ones. The number of RSV-related LRTI/LRTD cases was reduced by vaccination, with a relative risk of 0.39 [CI 95% 0.22 to 0.69] and a vaccine efficacy of 61%. Considering the subgroup of prefusion vaccines alone, there is a relative risk of 0.27 [CI 95% 0.19 to 0.36] for LRTI/LRTD and a vaccine efficacy of 73%. ARI/ARD incidence presented a similar pattern. Only one trial reports results for severe LRTI/LRTD, with a vaccine efficacy of 94.1% [95% CI 62.4 to 99.9].

Conclusions: Prefusion anti-RSV vaccines are efficacious in the prevention of LTRI/LTRD and ARI/ARD cases. More studies regarding severe LTRI/LTRD are necessary in the future.