Clinical spectrum and complications of childhood pneumonia in the era of bacterial conjugate vaccines

Abstract

Pneumonia remains a leading cause of under-5 childhood mortality, particularly in low and middle-income countries. The rollout of conjugate bacterial vaccines, including Haemophilus influenzae type b conjugate vaccine (HibCV) and particularly pneumococcal conjugate vaccine (PCV), into national immunization programs recently, has been associated with dramatic decline in all-cause pneumonia hospitalization in many developed countries where PCV immunization has been implemented. Also, PCV immunization has variably been associated with changes in incidence of hospitalization due to influenza virus and RSV-associated pneumonia in some settings. There is, however, limited data from low and middle-income countries on the effectiveness of PCV against pneumonia once introduced into immunization programs. A broader diversity of serotypes associated with pneumococcal disease and higher prevalence of underlying risk factors for pneumonia such as greater prevalence of malnutrition, HIV-infection and tuberculosis may affect the impact of PCV on all-cause pneumonia morbidity and mortality in children. Furthermore, early experience from few studies in developed countries with 7-valent PCV, suggested a temporal association between PCV-7 introduction and an increase in complicated pneumonia including that due to empyema due to few serotypes not included in PCV7, but which are now included in the 10 and 13-valent PCVs formulations currently used. The global public health value of PCV will be measured by its success in reducing all-cause childhood pneumonia morbidity and mortality in low and middle-income countries. Results on the impact of PCV immunization in early-adopting low and middle incoming countries are imminent and will contribute in determining the potential of PCV in improving child health globally.