According to GiveWell's Cost-Effectiveness Analysis (CEA), mass deworming ranks among the very best global health interventions. The evidence for deworming comes primarily from a single study, which showed large economic effects which were present a full decade after treatment. However, other studies have shown little to no effect of mass deworming on weight, cognitive ability, school attendance or other health outcomes, and the weight placed on the initial paper has proved controversial.

In GiveWell's CEA, deworming benefits are modeled as being entirely due to long-term economic effects like those seen in the study mentioned above. Despite being heavily discounted due to concerns about replicability, in expectation these economic effects are expected to dominate the short term health effects of the interventions.

Givewell's position is explained, in detail, in the following two blog posts:

• Why I mostly believe in Worms

• How thin the reed

Some more information is available in this evidence overview, written by GiveWell, which cites several papers, and this evidence overview, which was written by Evidence Action. While Evidence Action does currently run a deworming programme, they have proved capable of changing their minds on programmes when the evidence changes.

Currently, GiveWell lists seven top charities, of which four are deworming programmes.