Impacts of Nutrition, Vaccination and Seasonal Drivers on Respiratory Infection Dynamics in Laikipia, Kenya

Abstract

Pneumonia is the top killer of children under five years old worldwide, taking the lives of 1.2 million children every year. Developing countries bear the highest burden of mortality, and 30,000 of these yearly childhood pneumonia deaths occur in Kenya. To curb disease, the Kenyan government, with the GAVI Alliance, introduced the 10-valent pneumococcal conjugate vaccine (PCV) to the routine immunization schedule without cost for all infants in 2011. This thesis examined the efficacy of the PCV campaign in pastoralist populations in Northern Kenya, and assessed interactions between nutrition, vaccination, seasonal drivers and disease. These populations are remarkably poor and have limited access to food and healthcare, making them an interesting case study of the campaign’s efficacy in populations that need prevention most. This thesis was divided into three parts. First, we assessed risk factors for respiratory infections in this population through a case-control study. We found that nutritional status does not significantly affect odds of respiratory infections, but does put children at increased odds of diarrhea. No significant relationship between vaccination and odds of respiratory infections was found. Next, we examined the clinic records of two local outpatient facilities to determine the effect of vaccination at the population level. Pneumonia prevalence has not changed at either clinic with vaccination; however, at the Kimanju Dispensary, respiratory tract infections (RTI) have significantly decreased with vaccination, and upper respiratory infections (URTI) have increased, signifying potential serotype replacement or competitive release. Finally, the impact of seasonal drivers on respiratory infections was assessed. The infections examined increased with rainfall and vegetation and decreased with higher daily temperature differences, with different time lags associated with each seasonal driver and infection.