Health Interventions and Health Equity

Introduction

This article examines the role of direct health interventions and their effect on health inequity, defined as the differences in "health status, risk factors, or health service utilization between individuals or groups." The authors approach this issue by assessing the impact of a measles vaccination programme on the gender and socioeconomic differences associated with childhood mortality within Bangladesh. They highlight three key disparities that are reflected in differences in: 1) disease prevalence, 2) personal illness control, and 3) intervention effectiveness. They examine these differentials over time using a large volume of longitudinal data provided by the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B), which has been undertaking continuous surveillance in the Matlab area since 1966. The authors conclude that while long-term efforts to reduce disparity are important, short-term efforts such as a measles intervention programme can have pronounced effects on child survival. The authors conclude that measles vaccination should remain a high priority within child survival efforts.

Key Findings

The authors begin by noting that many studies over the last 20 years have shown that in-country, differential infant, and early-childhood mortality rates are widespread throughout developing countries and linked to socioeconomic status. Possible solutions to this problem are widely debated and include both direct and indirect measures. The focus for the authors is on direct measures, specifically on child immunisation. There are three main explanations for differentials in health, disease prevalence, personal illness control, and intervention efficacy; this study primarily focuses on the impact of the last of these explanations. The authors ask "whether the most vulnerable children may actually benefit disproportionately from a child survival intervention in terms of improved survival prospects." They seek to answer this question by evaluating whether the Matlab measles vaccination programme has influenced existing socioeconomic differentials with regard to overall mortality risks. Do female children and children from poorer families disproportionably experience improved survival after measles vaccination?

The Matlab intervention project was introduced in 1977 into half of the study area, the intervention area, while the remainder stayed as a comparison. The intervention area received increased preventative and curative support and resources for diarrhoeal diseases and subsequent introduction of nutrition management, vitamin A, and other services. In 1982 a measles vaccination programme was started in the intervention half; measles vaccination was introduced into the other half in 1985. The authors use this quasi-experimental design to assess differences in child mortality between children included in the first half and those included in the second half. Analysis had shown that the two halves had nearly identical mortality rates prior to the measles project. All children aged 9-60 months from the first half were randomly matched with unvaccinated children of similar age from the second half. All children were followed from the time of the vaccination of the one child in the pair until death, out-migration, or the completion of the study in 1985.

The results were considerable, and subsequent differentials in mortality were statistically significant. The impact of gender inequities was pronounced, and the cumulative deaths over the 42 months of vaccinated girls (approx. 60 deaths p/1000) was equal to that of unvaccinated boys, a substantial absolute reduction in female mortality (from approx. 98 deaths p/1000). The study also found that the impact of the measles project was most pronounced upon poorer children. The study used household dwelling size as a stand-in measure of economic status in rural Bangladesh. The impact was greatest amongst children who resided in dwellings of 200 sq ft (lowest economic status) or less (from approx. 100 to 55 deaths p/1000), had a substantial but lesser effect on children whose dwelling size of 201-400 sq ft (from approx. 64 to 39 deaths p/1000), and was not a significant factor in reducing the amount of deaths in children whose dwelling size exceeded 400 sq ft (highest). This same phenomenon is repeated when the independent variable is mother's education. Those with no education saw the greatest relative reductions in risk of death, with a significant but smaller improvement amongst mothers with 1-5 years of education and results that were insignificant for women with 6+ years of education.

The authors also performed an extensive multivariate analysis, using a "proportional hazard analysis" model that included sex, mother's education, religion (Hindu/Muslim), and dwelling size that gave an overall economic status (ES) category. The impact once again showed the greatest relative risk reduction amongst children that were in the lowest ES category. In addition, the impact of the measles programme was found to be significant in explaining reductions in mortality amongst Muslim children (who also have historically had higher mortality rates).

The authors' conclusion is that short-term, limited interventions such as measles vaccination programmes can have tangible effects on health inequities and should be considered as complementary to the long-term efforts aimed at reducing disparity. They note that an unvaccinated child from a poor family has a three times higher risk of early childhood mortality compared to a vaccinated child from a high economic status family. The introduction of a measles vaccination programme alone lowers the risk for the poor child to only 1.5 times that of the wealthier child. However, the authors are cautious, noting that there are variances in the contribution that measles makes to mortality between countries. The authors also address several issues that may undermine their study related to selection bias amongst children being offered up for vaccination, and also admit that the variable related to house size may be a stand-in for crowding (and its effect on disease transmission and health) rather than a measure of ES. Nevertheless, the authors are confident that saving a child from death by measles contributes to his or her overall long-term survival chances in other ways. They conclude by arguing that their findings provide further support to the current arguments that support the universal provision of measles vaccination, and encourage it to be made a high priority within child survival programmes.