A U.S. President's Malaria Initiative VectorLink Project study in western Kenya shows one round of indoor residual spraying (IRS) with pirimiphos-methyl is highly effectively at providing year-round protection against the indoor biting and resting pyrethroid-resistant An. funestus mosquitoes. The spraying reduced the number of mosquitoes and malaria cases. The study found less impact on An. arabiensis, likely due to its outdoor-biting and resting behavior. That vector requires additional control measures. The study appears in the peer-reviewed Scientific Reports, the 11th most cited journal in the world.