Objective: To determine whether Bacille Calmette-Guerin (BCG) vaccination is linked to the risk of acute lower respiratory infection (ALRI) among children <5 years of age.
Methods: Data from Macro International Demographic and Health Surveys and United Nations Children's Fund Multiple Indicator Cluster Surveys were used to identify a primary cohort of 58,021 children in 19 countries (2005-2010) and a secondary cohort of 93,301 children in 18 countries (2000-2007). Information was collected by trained interviewers during home visits using standardized questionnaires, review of vaccination health cards, and measurement of health indicators.
Results: BCG vaccination was associated with a 17% to 37% risk reduction for suspected ALRI in both cohorts. The only vaccine or vitamin supplement to modify the effect of BCG was diphtheria-tetanus-pertussis (DTP; P < .001). The order in which the vaccines were first received was central to this phenomena (BCG before DTP, adjusted/propensity score-weighted relative risk [apRR]: 0.79, 95% confidence interval [CI]: 0.70-0.89; BCG with DTP, apRR: 0.82, 95% CI: 0.71-0.94; and BCG after DTP, apRR: 1.00, 95% CI: 0.87-1.13) but not number of DTP doses received. Other modifiers included vaccine strain used in immunization programs, chlorinating drinking water, using wood-burning fuel cook stoves, and owning livestock.
Conclusions: Children vaccinated with BCG had a significantly lower risk of suspected ALRI. Clarification is needed as to whether this is due to reductions in the underlying risk of tuberculosis or ALRI per se.
Keywords: Bacille Calmette-Guerin (BCG) vaccine; childhood immunization; developing countries; diphtheria-tetanus-pertussis (DTP) vaccine; respiratory tract infection.