Mosquito nets infused with two pesticides work much better against malaria than those with only one, reducing prevalence in children by 44 percent, according to a recent study.

As a result of the report, published in The Lancet last month, the World Health Organization has recommended that the two-chemical nets be used in areas where mosquitoes have developed resistance to the first-line insecticide.

The new nets contain pyrethroids, a class of chemicals used in nets for over a decade, along with the newer compound, piperonyl butoxide, which blocks mosquitoes’ ability to break down pyrethroids. (It is sometimes called a “pesticide synergist.”)

The Vestergaard company, which introduced pyrethroid-infused nets in 2004, later developed a two-chemical version that the W.H.O. began evaluating in 2014. Now many companies have similar nets awaiting W.H.O. approval.