Pneumococcal Conjugate Vaccines Are Protective Against Respiratory Syncytial Virus Hospitalizations in Infants: A Population-Based Observational Study

Abstract

Background: Pneumococcal conjugate vaccines (PCV) reduced the risk of respiratory syncytial virus (RSV) in a randomized clinical trial. We aimed to assess the real-world effectiveness of PCV on RSV-hospitalizations among Western Australian infants. Methods: We conducted a population-based cohort study of births during 2000-2012, using probabilistically linked individual-level immunization, hospitalization, respiratory microbiology testing, and perinatal data. We performed Cox proportional hazard models with time-varying exposure (receipt of infant PCV doses) against the first RSV-confirmed hospitalization 0-12 months adjusted for perinatal and sociodemographic factors. Results: From 360 994 children, 3-dose PCV coverage in Aboriginal infants ranged from 29% to 51% in 2001-2004 when PCV was funded for Aboriginal children only. Following universal funding in 2005, coverage increased to 85% for Aboriginal and 73% for non-Aboriginal infants. RSV-hospitalization rates were highest in young infants aged 0-5 months (22.5/1000 child-years) and >2 times higher in Aboriginal infants than in non-Aboriginal infants. Receipt of ≥3 PCV doses in the universal funded period was associated with a 30% reduction in RSV-hospitalization in Aboriginal infants (adjusted hazard ratio, aHR 0.70 [95% confidence interval, CI 0.46-1.06]) and 21% reduction in non-Aboriginal infants (aHR 0.79 [95% CI 0.63-0.99]) compared with unvaccinated infants. Conclusions: Prior to the introduction of RSV vaccines, our study suggests that universal childhood PCV vaccination may result in a reduction in severe RSV infections in children and may be important for countries that are yet to consider PCV programs.