NONSPECIFIC BENEFICIAL EFFECT OF MEASLES IMMUNIZATION - ANALYSIS OF MORTALITY STUDIES FROM DEVELOPING-COUNTRIES

Objective-To examine whether the reduction in mortality after standard titre measles immunisation in developing countries can be explained s imply by the prevention of acute measles and its long term consequence s. Design-An analysis of all studies comparing mortality of unimmunise d children and children immunised with standard titre measles vaccine in developing countries. Studies-10 cohort and two case-control studie s from Bangladesh, Benin, Burundi, Guinea-Bissau, Haiti, Senegal, and Zaire. Main outcome measures-Protective efficacy of standard titre mea sles immunisation against all cause mortality. Extent to which differe nce in mortality between immunised and unimmunised children could be e xplained by prevention of measles disease. Results-Protective efficacy against death after measles immunisation ranged from 30% to 86%. Effi cacy was highest in the studies with short follow up and when children were immunised in infancy (range 44-100%). Vaccine efficacy against d eath was much greater than the proportion of deaths attributed to acut e measles disease. In four studies from Guinea-Bissau, Senegal, and Bu rundi vaccine efficacy against death remained almost unchanged when ca ses of measles were excluded from the analysis. Diphtheria-tetanus-per tussis and polio vaccinations were not associated with reduction in mo rtality. Conclusion-These observations suggest that standard titre mea sles vaccine may confer a beneficial effect which is unrelated to the specific protection against measles disease.