Non-Specific Sex-Differential Effect of the Routine childhood Vaccinations in a Poor Urban Informal Settlement, Nairobi, Kenya
Studies mainly done in west Africa have suggested influence on child mortality by the routine childhood vaccination in a way more than protecting from the targeted diseases, and have been shown to be sex depended. This study tests the effects of gender on child mortality for unvaccinated children and also those exposed to BCG, DTP and measles vaccine in an urban informal settlement area
METHODS:
All live births in two informal urban settlements in Nairobi, Kenya were followed from 2006 to 2013 until 31 December 2013 or 36 months of age whichever was earlier. The period of analysis was divided into four time periods based on eligibility for the routine child vaccination. Cox proportional hazards regression was used to assess the association between gender and risk of mortality by vaccination status using age as the timescale in survival analysis and adjusting for wealth index, access to health care, mother education, parity, mother age.
RESULTS:
323 deaths (164 boys and 159 girls) occurred among 8760 children during the period of follow-up with a cumulative mortality rate of 36.8 per 1000 live births with 6% excess girl child mortality. Age at vaccination for the three vaccines did not differ by sex. Unadjusted hazards ratio estimates showed higher mortality in girls for children not exposed to any vaccines 1.32 (0.91-1.94) or those exposed to DPT 1.01 (0.71-1.42) but lower mortalities after exposure to BCG 0.93 (0.71–1.23) or measles 0.98 (0.56–1.72) vaccine
CONCLUSIONS:
This study shows mortality is higher in unvaccinated girls as compared to unvaccinated boys. Unadjusted estimates also shows higher mortality in girls after exposure to DPT vaccine.