Background: The World Health Organization recommends that pneumococcal conjugate vaccines (PCVs) be included in childhood immunization programs worldwide. The cost of a PCV vaccine is daunting to many low- and middle-income countries. In these settings, targeted vaccination strategies may ultimately be more sustainable until financing is available for universal roll-out.
Methods: We analyzed data from 11,729 children enrolled in a randomized, placebo-controlled, double-blind trial which examined the efficacy of an 11-valent pneumococcal conjugate vaccine (11PCV) in children less than 2 years of age in Bohol, Philippines. Study endpoints included radiographic pneumonia and clinical pneumonia classified using WHO definitions (nonsevere, severe, and very severe). Observed variation in vaccination and pneumonia case-rates over space and time necessitated a spatio-temporal approach to modeling. Cox's proportional hazard models with spatio-temporally varying risk factors were used to estimate the risk of pneumonia infection between time at 3rd dose to age 24 months.
Results: Children with pneumonia were more likely to be boys, had a lower weight-for-age z-score, a mother with a lower level of education, came from households with more children, and lived closer to Bohol Regional Hospital [BRH] (p<0.01). A significant interaction effect between distance from BRH and vaccination with 11PCV indicated a reduction in risk for vaccinees living further from health services (Figure 1). For radiographic pneumonia, the HR decreased from 1.11 (95% CI 0.84-1.45) for children living 1km or less from BRH to 0.60 (95% CI 0.40-0.88) for children living 10km or more from BRH. Results were similar for severe/very severe pneumonia. We also found a significant increase in risk of severe/very severe pneumonia for children living 1 km or less from BRH (HR 1.24, 95% CI 1.03-1.49). There was no significant interaction effect among children with non-severe pneumonia.
Conclusion: Children living a greater distance from comprehensive health services derive greater benefit from vaccination with 11PCV. This study provides important information that can potentially be used for targeting public health interventions in the Philippines, and perhaps other similar settings.
E. D. Root,
H. Nohynek, None
V. Tallo, None
R. Stubbs, None
E. A. F. Simões, None