11-PCV Trial Study Area – Bohol, Philippines
The etiology of lower respiratory tract infections (LRIs) in developing countries has been studied extensively in the 1980’s (BOSTID studies). However, little research has examined spatial and spatio-temporal patterns of acute lower respiratory infections or vaccine efficacy. Geographic analysis of infectious disease and vaccine efficacy may serve to shed important insights on the etiology and transmission dynamics of the disease. The identification of spatial and temporal factors associated with disease incidence may suggest target risk factors or environmental conditions that can be used for efficient and cost-effective vaccine implementation and may provide insight into the role of spatial distribution of vaccination rates and herd immunity in widespread vaccination campaigns.
A common barrier to geographic analysis is the quality and availability of incidence and vaccine data; in most cases, particularly in lower-income contexts, this kind of analysis is not possible because data are only partially complete or are aggregated by hospitals or statistical-administrative units. In the 11-Valent Pneumococcal Conjugate Vaccine trial in the Philippines, the residential addresses of over 12,000 infants and children, 2000 hospital visits, and 3000 emergency department visits were recorded and mapped, making it possible to perform detailed analysis on the spatio-temporal dynamics of respiratory infections. Further, this study had an enrollment rate close to 98% of all infants born into the study area. The comprehensive and detailed nature of this study data, paired with available geographic data of Bohol, enables us to perform comprehensive and unprecedented geospatial analyses.
Spatial Distribution of Vaccinated Children
The ongoing goal of this study is to analyze patterns of: a) severe pneumonia, as defined by the World Health Organization; b) radiographic pneumonia; c) incidence rates among vaccinated and placebo groups; d) vaccination rates; and e) vaccine protective efficacy. To date, descriptive geographic analysis has identified spatial and temporal patterns of vaccination and pneumonia rates. Results also indicate that vaccination with 11-PCV was not spatially random despite infants being randomized into the study at the individual-level. Vaccine efficacy also shows strong spatial patterns with some areas exhibiting close to 50% efficacy, and others showing negative efficacy. In addition, patients residing a further distance from the main area hospital are more likely to develop severe cases of LRI and derive greater benefit from the vaccine. This study used descriptive mapping and spatial regression analysis with ecological and neighborhood variables to model LRI incidence and vaccine protective efficacy.
This project is in collaboration with:
The ARIVAC Consortium
Eric Simoes (Dept of Pediatrics, Children’s Hospital Colorado)
Publications
Distance to health services affects local-level vaccine efficacy for pneumococcal conjugate vaccine (PCV) among rural Filipino children. 2014. Proc Natl Acad Sci USA.
Disease mapping for informing targeted health interventions: Childhood pneumonia in Bohol, Philippines. 2015. Tropical Medicine and International Health.