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Routine vaccinations and child survival: follow up study in Guinea-Bissau, West Africa
I Kristensen1, P Aaby, H Jensen
1Bandim Health Project, Apartado 861, Bissau, Guinea-Bissau.
Objective:
To examine the association between routine childhood vaccinations and survival among infants in Guinea-Bissau.
Design:
Follow up study.
Participants:
15 351 women and their children born during 1990 and 1996.
Setting:
Rural Guinea-Bissau.
Main Outcome Measures:
Infant mortality over six months (between age 0-6 months and 7-13 months for BCG, diphtheria, tetanus, and pertussis, and polio vaccines and between 7-13 months and 14-20 months for measles vaccine).
Results:
Mortality was lower in the group vaccinated with any vaccine compared with those not vaccinated, the mortality ratio being 0.74 (95% confidence interval 0.53 to 1.03). After cluster, age, and other vaccines were adjusted for, BCG was associated with significantly lower mortality (0.55 (0.36 to 0.85)). However, recipients of one dose of diphtheria, tetanus, and pertussis or polio vaccines had higher mortality than children who had received none of these vaccines (1.84 (1.10 to 3.10) for diphtheria, tetanus, and pertussis). Recipients of measles vaccine had a mortality ratio of 0.48 (0.27 to 0.87). When deaths from measles were excluded from the analysis the mortality ratio was 0.51 (0.28 to 0.95). Estimates were unchanged by controls for background factors.
Conclusions:
These trends are unlikely to be explained exclusively by selection biases since different vaccines were associated with opposite tendencies. Measles and BCG vaccines may have beneficial effects in addition to protection against measles and tuberculosis.