Social determinants of low uptake of childhood vaccination in high-risk squatter settlements in Karachi, Pakistan - A step towards addressing vaccine inequity in urban slums

Background: Routine vaccination has remained historically low in major urban pockets of Pakistan, and now lags behind rural vaccination rates. Grossly insufficient publicly funded primary healthcare infrastructure, heterogeneous mix of providers and multi-ethnicity of populations pose challenges in the delivery of essential health services. This paper ascertains factors associated with uptake of routine childhood vaccination, using Pentavalent-3 vaccine, as a proxy indicator for completion of age-appropriate vaccines in urban slums of Karachi, at high risk of Polio and vaccine preventable disease outbreaks. Methods: Data was drawn from baseline assessment of an urban immunization delivery pilot project in urban slums of Karachi, Pakistan. The study sample comprised of 2,097 households with children aged 4-12 months, sampled through a cross-sectional cluster survey, applying a structured questionnaire. Multivariable logistic regression was used to determine the association between Penta-3 vaccination, as the outcome variable, and predictor variables including socio-demographic characteristics and healthcare access factors. Results: The findings showed that the likelihood of being immunized with Penta-3 was higher for non-Pashtun ethnicity [adjusted odds ratio (aOR) 1.69; 95% CI 1.33-2.14], children of educated mothers, secondary or higher [aOR 2.95, 95% CI 2.34-3.71], and those whose fathers were formally employed (aOR 1.53; 95% CI 1.19-1.97). No association was seen by gender of child [aOR 0.89; 95% CI 0.73-1.08], and place of new born delivery [aOR 1.01; 95% CI 0.83-1.24]. Conclusion: Pockets of critically low under-vaccinations within the urban slums of Karachi are associated with Pashtun ethnicity, distance to the vaccination centre, lack of mothers' education and lack of stable family income as in the case of unemployed and daily wage-earning fathers. Recognition of these factors is required in designing contextually appropriate strategies to address vaccine inequity in urban settings.