Deworming in schools: policy design insights

According to the estimates for March 2020 of the World Health Organization (WHO), more than 1.5 billion people -roughly 24% of the population, were infected with soil-transmitted helminth infections (intestinal worms).^[1] The burden of the disease is mostly carried by developing countries located in sub-Saharan Africa, the Americas, and East Asia. The number would be even higher if it were not for multiple efforts to interrupt transmission to the disease. Addressing these infections in school-age children has been a priority for many years, as the worms feed on their blood, prevent them to absorb their nutrients, and suppress the children’s appetites.^[2] This disruption prevents kids from getting proper nutrition,^[3] which hinders growth and physical development.^[4]

The main intervention to deal with this public health issue has been mass drug administration (MDA) of albendazole or mebendazole.  The WHO’s position is that in areas where the prevalence of any soil-transmitted infection is 20% or more. Such mass administration consists of an annual or biannual dose for cases where the prevalence is more than 50%.^[5]

MDA programs can be implemented in different ways, however, one of the most successful interventions has been school-based. In this last modality, medicine is directly delivered to the kids through the professor on designated days. Such design is feasible because the medication is deemed safe,^[6] even for those who are not affected by the disease, it is low-cost and can be administered without the need of specialists. Moreover, MDA is favored as targeting through the screening of the disease is significantly more expensive^[7] and does not provide additional benefits. Significant savings also come from the fact that these interventions do not require additional infrastructure, rather make use of existing schools. This design also has the advantage of ensuring compliance, as children take their treatment on the school grounds.

The characteristics of these programs allow us to identify important factors in policy design, for instance how to guarantee compliance of the treatment and if it is possible to leverage already existing resources to improve the cost-effectiveness of the intervention. Moreover, these interventions are also interesting because they open a discussion about their benefits, more specifically which benefits do we consider when measuring the cost-effectiveness of a program. In the case of MDA, the impact on several health outcomes can be evaluated, such as weight gain, mortality, the likelihood of stunt, anemia prevalence, etc. However, evidence shows that focusing only on these variables might not account for all the social benefits of these programs. For instance, school-based deworming has been identified as an effective way to increase school attendance in different randomized trials.^[8] Moreover, long-term studies of those treated in Kenya show that 20 years after the intervention, that individuals who received 2 to 3 additional years of school deworming had an increase of 13% in hourly earnings.^[9]

Although MDA seems like an ideal intervention, these programs have faced significant criticism, with some studies claiming that the interventions have had no significant effect on health outcomes. As there have been specific rebuttals of such studies,^[10] MDA programs are still widely supported. While in general, the evidence for these programs suggests they are effective, there are indeed some cases in which the interventions have not yielded the expected results. This led us to another important factor in policy design: context. In this sense, even if the medications themselves have proven to be successful, sustainable interruption of the infections can only happen if other characteristics of the environment are addressed as well. In this sense, it is important to consider the transmission mode of the disease: water or soil contaminated with the fecal matter of infected people.^[11] This means that proper access to water and sanitation is key, as well as proper education to adequately use such resources. In addition, other characteristics, such as the climate can be relevant for the intervention.^[12]

While there have been other factors why the intervention has not been successful in some cases, MDA highlights that when attempting to replicate or scale up a “successful” intervention, we must always consider the heterogeneity of our surroundings.

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