Deworming children in developing countries has for a while been thought of as one of the best bang per buck interventions (link 1, link 2). Recently a systematic review (basically someone looks for every article ever written about a subject in a systematic fashion) suggested the results of dewormings impacts might not have been as good as touted in their conclusion the authors state
"Our interpretation of this data is that it is probably misleading to justify contemporary deworming programmes based on evidence of consistent benefit on nutrition, haemoglobin, school attendance or school performance as there is simply insufficient reliable information to know whether this is so."
Two groups IPA and J-PAL have issued a joint response saying the systematic review is misleading.
My take having done a systematic review (not of deworming, but instead of cash transfer impacts on nutrition) is that the authors likely found nearly all of the relevant evidence. IPA and J-PAL point to three papers not included. I'm familiar with the Kenyan papers and think highly of both of them. However, I believe the might not add as much as other potential studies as there was already evidence from Kenya that deworming works (see the famous Kremer and Miguel paper).
I think both sides should take this as a call to test the external validity of deworming, do you get equal bang for the buck in other deworming contexts. As this post suggests all worms might not have equal impacts and if different worms are in different places, we would expect different impacts.