Decline in Community-Acquired Alveolar Pneumonia Positive for Respiratory Syncytial Virus in Hospitalized Children Following Implementation of Pneumococcal Conjugate Vaccine (PCV) in Israel

BACKGROUND: We assessed the impact of pneumococcal conjugate vaccine (PCV) implementation on respiratory syncytial virus-positive, community-acquired alveolar pneumonia (RSV-CAAP) in young children in southern Israel. METHODS: This study was nested within a prospective population-based active surveillance system during 2004-2019. All children <60 months old residing in the region and served by the region's only hospital were included. A negative binomial regression model was used to evaluate the impact of PCV on the incidence of all-cause CAAP and RSV-CAAP and was the basis for estimating averted episodes. RESULTS: A total of 7640 all-cause CAAP episodes were observed; 50% were tested for RSV, of which 42% were positive. Shortly after PCV13 implementation, all-cause CAAP and RSV-CAAP rates markedly declined, stabilizing within 3-4 years. The mean annual hospitalization rates for all-cause CAAP and RSV-CAAP declined by 47% (95% CI: 40%-53%) and 29% (95% CI: -2% to 51%), respectively, during the late-PCV period, compared with the expected rates. This translated to a reduction in the mean annual incidence of 3.73 cases of all-cause CAAP/1000 children (95% CI: 2.98-4.58) and 0.50 cases of RSV-CAAP per 1000 children (95% CI: -.05 to 1.13). The highest incidences of averted cases occurred in children aged 12-23 months. CONCLUSIONS: The observed dynamics of hospitalizations due to all-cause CAAP and RSV-CAAP following PCV implementation are consistent with the notion of a synergistic role of RSV and pneumococcus in CAAP in young children.