Respiratory syncytial virus vaccine: a systematic overview with emphasis on respiratory syncytial virus subunit vaccines.

OBJECTIVE: To explore whether RSV vaccines are efficacious in preventing respiratory syncytial virus (RSV) lower respiratory infection (LRI).
METHODS: Randomized clinical trials were sought through Medline using the following search terms: "RSV" or "RSV infection" and "viral vaccine". Randomized controlled trials in adults or children that provided data on clinical outcomes (RSV LRIs, all LRI, all RSV infections) were included. Control groups could receive placebo or another vaccine. Qualitative assessment and summary data were obtained independently by three authors and summarized on a pre-printed form. Where disagreements occurred, the studies were reviewed by all investigators. These disagreements were mainly clerical, such as misinterpretations of the table or text or transcription errors. Consensus was obtained for all studies. Summary statistics consists of relative risk (RR) and number needed to vaccinate to prevent the above outcomes.
RESULTS: Because of the outcomes examined, only studies of a purified F protein subunit (PFP) vaccine were included in the meta-analysis. These clinical trials were phase I studies to determine vaccine safety rather than efficacy. Efficacy of PFP-1 or PFP-2 vaccine were analyzed together. A statistically significant RR in overall number of RSV infections was observed RR 0.55 (95%CI, 0.35, 0.88), but the test of heterogeneity was significant raising doubts about the validity of this conclusion. The effect of vaccination on RSV LRI did not reach statistical significance.
CONCLUSIONS: RSV subunit vaccines were found to reduce the overall incidence of all RSV infections. However, RSV subunit vaccines must be tested in large field trials because of concerns about the appropriateness of pooling, the risk of publication bias and the fact that the clinically important outcome of RSV LRI was not reduced.