Impact on Infection Intensity: Deworming reduced serious worm infections by half amongst children in the treatment groups. Pupils that received treatment reported being sick significantly less often, had lower rates of severe anemia, and showed substantial height gains, averaging 0.5 centimeters.
Impact on School Attendance: Deworming increased school participation by at least 7 percentage points, which equates to a one-quarter reduction in school absenteeism. When younger children were dewormed, they attended school 15 more days per year, while older children attended approximately 10 more school days per year. The larger impact of treatment in lower grades may partially result from higher rates of infection among younger pupils.
Treatment Spillover: The entire community and those living up to 6 kilometers away from treatment schools benefited from “spillovers” of the deworming treatment. Spillover effects occur because medical treatment reduces the transmission of infections to other community members. Reductions in infection in non-treated children resulted in an additional 3 to 4 days of schooling per year. Although data was not collected on adults, it is also likely that older community members were able to work more days as a result of spillover effects.
No improvements in test scores were found as a result of the deworming. Additionally, evidence suggests that health education had a minimal impact on behavior, so that to the extent that the program improved health, it almost certainly did so through the effect of the medicines rather than through health education. Including the spillover benefits of treatment, the cost per additional year of school participation is US$3.27, considerably less than the cost of many alternative methods of increasing primary school participation.