IRS refers to the application of insecticide onto the interior walls of houses. The study, by the Wits Research Institute for Malaria (WRIM) and the London School of Hygiene and Tropical Medicine (LSHTM), was published in The Lancet on 25 February 2021. Targeted vs blanket Indoor Residual Spraying Malaria still represents one of the world's largest health crises, particularly on the African continent where 94% of cases and deaths occur (World Health Organization, 2020). Most countries in southern Africa have set the elimination of malaria within their borders as a policy target. In South Africa, IRS has been effectively used since 1945. As a result, malaria transmission is low, but persistent. Malaria transmission is confined to the north-eastern border districts of Mpumalanga, Limpopo, and KwaZulu-Natal provinces.