Polio supplementary immunization activities and equity in access to vaccination: evidence from the demographic and health surveys.

Every year, large numbers of children are vaccinated against polio during supplementary immunization activities (SIAs). Such SIAs have contributed to the >99% decline in the incidence of poliovirus cases since the beginning of the Global Polio Eradication Initiative. It is not clear, however, how much they have also contributed to reducing poverty-related inequalities in access to oral polio vaccine (OPV). We investigated whether the gap in coverage with 3 doses of OPV between children in the poorest and wealthiest households was reduced by SIA participation. To do so, we used data from 25 demographic and health surveys (DHS) conducted in 20 countries since 2002. We found that, in several countries as well as in pooled analyses, poverty-related inequalities in 3-dose OPV coverage were significantly lower among children who had participated in SIAs over the 2 years before a DHS than among other children. SIAs are an important approach to ensuring equitable access to immunization services and possibly other health services.