Impact of the national polio immunization campaign on levels and equity in immunization coverage

Introduction

This study investigated the impact of the national polio immunisation campaigns in northern India on overall sustainability of routine polio vaccination, on coverage of non-polio vaccines, and on the inequality of vaccine coverage attributable to socioeconomic factors. The authors used a before and after study design to assess how the commencement of the national Pulse Polio Immunization (PPI) campaign in 1995 affected these issues. While improvements in the level of first dose and three dose coverage of polio vaccine were observed, little improvement was recorded with regard to non-polio Expanded Program on Immunization (EPI) goals, a finding that contradicts advocates who have suggested that PPI contributes to routine immunisation. Furthermore, while PPI contributed to closing some socio-economic gaps in coverage, others were unchanged.

Key Findings

The authors used the data from the National Family Health Survey I (NFHS I) and NFHS II, carried out in 1992-93 and 1998-99, respectively, to measure the impact of the commencement of the PPI programme in 1995. The data was drawn from rural areas in the four northern states of Bihar, Madyha Pradesh, Rajasthan and Uttar Pradesh - the areas that remain major reservoirs of wild polio virus in India. The authors sought to evaluate the conventional wisdom that suggests that mass campaigns will improve coverage of routine immunisations (of both polio and non-polio vaccines) by increasing awareness, and that campaigns will reduce the socially determined inequalities associated with, and impinging on, routine immunisation.

There were four outcome indicators for this study, two related to polio vaccination and two related to non-polio vaccination (primarily measured by diptheria-pertussis-tetanus [DPT] and measles vaccination rates). The polio indicators were: whether the child had received the first dose of oral polio vaccine (OPV1), a measure of the overall number of children reached by the campaigns; and whether the child had received 3 doses of OPV (OPV3), which measures the overall capacity of health systems to ensure compliance/follow-up and allows for calculation of the dropout rate. The measures for the non-polio EPI vaccines were similar - 1 dose and 3 doses (DPT) or the full 5 doses (complete EPI). The independent, socioeconomic variables for the study included gender, caste, wealth, and religion of the child, as well as some village-level characteristics.

The authors found that the overall coverage rate of OPV1 had increased from 48% to 73% between 1993 and 1999. This improvement can be attributed to the PPI campaigns because the DPT1 rate increased from only 48% to 50%, and first dose DPT and OPV are almost always given together during routine immunisation. The improvement in OPV3 coverage was not as strong, increasing from 34% in 1993 to 45% in 1999, suggesting a dropout rate of 28 percentage points from the first to third doses of OPV. The DPT3 coverage did not change significantly, declining from 31% to 29%. The authors suggest the 16-percentage-point difference between the OPV3 and DPT3 rates can also be attributed to gains from the PPI campaign. The overall non-polio EPI coverage rate at one dosage improved marginally from 51% to 56%, but no significant change was recorded with regard to full immunisation (5 doses) coverage rates that remained at 18.4% in 1999. The conclusion from this data is that the campaigns are only really effective in improving the OPV coverage rates and have not had a significant effect on coverage rates of routine vaccination.

Multivariate analysis of the population subgroups revealed a mixed bag of improvements in coverage rates for some social determinants, while others remained unchanged. The gender gap, wherein boys are more likely to be immunised then girls, was almost eliminated for OPV1 coverage, and reduced for OPV3 (from 4.4% to 2.7% in 1999) but remained steady at 4.5% for full EPI vaccination. Wealth-based inequalities declined very little for both OPV1 and OPV3 and remained the same for EPI vaccinations, while the caste gap also declined somewhat, but remained statistically significant. Finally, while Muslim children showed improvement with regard to OPV1, moving from 33.7% to 69.6% coverage rates (compared to 49.9% to 72% for Hindu), they continued to have a 10-percentage-point gap in OPV3 coverage and a 5-percentage-point gap in full non-polio EPI vaccinations.

The authors sum up the results of their study by noting the following four points: (1) there were significant increases of coverage of first dose of OPV due to the PPI campaign, (2) there remained a significant drop-out rate between the first dose and the third dose despite the campaign, (3) there were moderate reductions in gender, wealth, and caste based inequities but none in religion or residence-based inequities, and (4) the PPI campaigns have had little effect on the levels and inequities of other non-polio EPI vaccinations.

They address these conclusions by suggesting that there may be inherent problems with the sustainability of the campaign approach (though they acknowledge that its purpose is not to be sustainable) and that its utility must be considered in light of the changing end-game scenarios related to polio eradication. The authors point out that the campaign's top-down nature makes it impossible for communities to gain a sense of ownership and places them in a lower position compared to other national and international priorities. Furthermore, long-term changes in preventative health behaviour cannot be implemented using the propaganda techniques associated with campaigns.

The authors also address the issue of the stagnant coverage rates of other non-polio vaccinations and suggest that the campaigns are not contributing to overall vaccination knowledge amongst the populations being addressed, and are not achieving the sometimes hypothesised synergies. Finally, the PPI campaign's mixed record in overcoming inequities in immunisation coverage may provide further lessons for long-term planning of routine vaccination and suggest that further research and the development of other complementary strategies is called for.