Determinants of Vaccine Coverage and Timeliness in a Northern Pakistani Village

"Families exposed to regular engagement with community health workers who promoted health education tended to be more likely to adhere to the EPI [Expanded Program on Immunization] schedule than families who came into the population later."

Considerable efforts have been made to understand the relatively low vaccine uptake in Pakistan, where there is ongoing, persistent wildtype 1 polio virus in circulation. This study examines the coverage and timeliness of vaccinations in Oshikhandass, a rural area in Northern Pakistan that has undergone substantial change, illustrated by investments in local education that increased maternal literacy from 29.3% to 71.7% (1989 to 2011). The study describes adherence to the Expanded Program on Immunization (EPI) schedule in children under 5 years born between 2011 and 2014, following an earlier, long-term cohort study (1989-1996) in the same community that included weekly visits from local healthcare professionals and promotion of childhood health best practices.

Vaccination histories were taken from EPI records. Vaccination was complete if all doses were received according to the EPI schedule and timely if doses were not 3 or more days early or 28 or more days late. Three models are presented: a multivariable logistic regression of household demographic and socioeconomic factors associated with complete vaccination, a multivariable mixed effects logistic regression assessing whether or not the vaccine was administered late (versus on time), and a mixed effects multivariable Poisson regression model analysing the interval (in days) between vaccine doses.

A total of 1,170 children under the age of 5 were enrolled into the study. Of these, 959 had full vaccination histories, with 88.2% and 65.1% fully vaccinated following either the pentavalent or diphtheria, tetanus, and pertussis (DPT)/Hepatitis B (HBV) schedules if measles was excluded; coverage dropped to 50.0% and 27.1% when both doses of measles were included. Sixty-four (6.7%) were unvaccinated. Coverage and timeliness declined with subsequent doses.

Migrating into the village after 1995 (95% confidence interval (CI) 1.88 to 5.17) was associated with late vaccination. Being male, having an older father, and having parents with at least some formal education reduced the likelihood of a late dose. The interval between doses was consistent at 5 weeks (compared with the 4 weeks recommended by EPI). None of the socio-demographic variables was related to the likelihood of receiving full coverage.

In short, this study found that vaccine coverage in Oshikhandass was higher than national averages, although measles vaccine coverage and timeliness were low. The local vaccination schedule differed from the EPI, but the consistency suggests good local administration.

The researchers point to substantial evidence of the potential of lady health worker (LHW)-type home-based health service programmes to improve outcomes for mothers and children. In Oshikhandass, LHWs were introduced in 1995, following an intensive child survival and health education programme that began in 1989. Contrary to previous studies that found limited use of vaccine cards and a lack of information for parents to counter misunderstanding about vaccines, in this population it was uncommon to lack vaccination documentation (18%) and rarer still to have received no vaccines at all (6.7%), suggesting that LHWs were instrumental in promoting vaccination.

In short, the strong community ties with LHWs "may account for some of the local successes of routine childhood vaccinations and promotion of similarly well-resourced LHWs could be a template to support timely vaccine acceptance....Improving vaccine availability and increasing interaction with community health workers have the potential to improve child survival through improved vaccine coverage."