Martin Kavao Mutua 2017

Mutua, Martin Kavao. 2017. Epidemiology and impact of vaccination coverage and delays in Korogocho and Viwandani informal settlements, Nairobi, Kenya, African Population and Health Research Center, College of Health Sciences, Jomo Kenyatta University of Agriculture and Technology.

Childhood Immunization has been identified as the most cost-effective health intervention in the last century. It is estimated to save more than two millions lives annually. Completion, timeliness and sequencing of routine vaccination as recommended by the World Health Organization is very crucial for maximum protection of children against specific infections. Existence of non-specific effects-effects other than prevention of specific infection–have been documented and could be linked to vaccination timeliness and sequencing. The objective of the study was to determine the prevalence and determinants of vaccination coverage and delays among children aged 12-23 months and establish the relationship with subsequent morbidity, anthropometry and, mortality in two Nairobi informal settlements. The study targeted households with children aged 12-23 months. Data from the Maternal and Child Health longitudinal study run by Nairobi Health and Demographic Surveillance System and collected between 2007 and 2014 was used. Structured data collection tools were used to collect data from mothers or guardians with children aged between 12 and 23 months. Proportions and medians were used to determine vaccination coverage and levels of delays respectively. Logistic regression models were used to identify determinants of full immunization and delays. Cox regression and Generalized Estimation Equation models were used to assess relationship between immunization patterns and morbidity, anthropometry and mortality respectively. The findings indicated that 67% of the children were fully immunized and 22% received their vaccinations out-of-sequence. Mother's education level, post-natal care, and health facility delivery were identified as the determinants of being fully immunized. Place of delivery was identified as the determinant of out-of-sequence. A significant 58% (p=0.017) and 64% (p<0.001) decreases in child mortality was observed for being fully immunized and immunized in recommended sequence respectively. A non-significant 35% (p=0.159) reduction in hospitalization cases was observed for being fully immunized. Vaccine completion was significantly associated with 0.13 (p=0.002) and 0.12 (p=0.006) increase in weight-for-age and weight-for-height z-scores respectively. More focus is needed on making sure all children are immunized on time and as per schedule. The low immunization coverage and age-specific vaccination can easily be improved by targeting disadvantaged groups. Particular attention is needed on the uptake of the measles and the third doses of polio and pentavalent vaccines. Further research is needed to determine the effects of each routine vaccine other than preventing the specific infection.


The overall coverage in the study was estimated at 67%. Coverage for specific antigens were all above 75% with low coverages observed for the third pentavalent vaccine dose, third polio vaccine dose and measles vaccine dose. High coverages were observed among BCG, first and second doses of polio and pentavalent vaccines. Vaccination delays of 15% to 39% were observed for the different vaccines and doses given to children in the study. Vaccination delays were higher in Korogocho compared to Viwandani. Early immunization was higher for the first doses of polio and pentavalent vaccines at 3.3% and 2.&% respectively. A fifth of children who were fully immunized by the age of 12 months had received their immunization in a different sequence from the recommended. The main source of out-of-sequence was identified as not receiving the respective pentavalent doses together as it is recommended. The main determinants of not being fully vaccinated by the end of one year of life were identified as children from mothers with lower education level, who did not attend post-natal care, did not deliver in a health center and from Korogocho area. Determinants of out-of-sequence among the fully immunized child were established as being from Korogocho area and not delivered in a health center. Better child health outcome have been shown to be associated with not only a child being fully immunized but there is an additional benefit for getting immunized in the recommended sequence.