Second-generation mosquito nets prevented 13 million malaria cases in large pilot programs

The fight against malaria is a test of human intelligence against mosquitoes — and so far, our minuscule winged enemy is winning. But new results shared this week show substantial improvements in one of the most important tools we have to prevent the life-threatening disease: bed nets.

Results shared this week by the New Nets Project, an initiative funded by Unitaid and the Global Fund, highlighted a pair of second-generation bed nets tested in endemic areas between 2019 and 2022. About 56 million nets were distributed in Burkina Faso, Benin, and Côte d’Ivoire, among other countries, and several pilot studies found that the new nets were between 20% and 50% more effective than traditional ones in reducing mosquito exposure and reduced the risk of infection by up to 55%. Overall, the New Net Project estimated the nets helped prevent up to 13 million additional cases of malaria, saving close to 25,000 lives.

The results come at a time when malaria cases have been on the rise. In 2022, the World Health Organization estimated there were nearly 250 million cases and more than 600,000 deaths, with 80% of deaths among children younger than 5. This is despite researchers’ growing understanding of mosquito behavior (including what scents attract them) and a growing list of cutting-edge tools that include two vaccines, treatments, gene-edited sterile mosquitoes, and malaria-sniffing dogs.

Nets have their downsides. They only last three years (or 20 washes), create waste, and at times are misused, causing serious environmental risks. But they save lives, and for two decades, nets treated with pyrethroid insecticide have been the go-to for protecting against mosquito bites. Mosquitoes have developed some resistance to pyrethroid insecticide, however, limiting the success of large bed net distribution programs.

Enter the second-generation nets tested in the recent pilot programs: Interceptor G2, produced by BASF, a chemical company, and Royal Guard, developed by Disease Control Technologies (DCT). The two nets were not compared head-to-head, so there is no conclusive data on which is more effective, though the Interceptor G2 nets, which are coated with chlorfenapyr as well as standard pyrethroid insecticide, always performed better than older generation nets, while the DCT nets, which use a combination of pyriproxyfen and pyrethroid, didn’t always have as clear-cut results, said Joe Wagman, the senior public health entomologist at the malaria and neglected tropical disease program of PATH, a charity focused on global health equity.

Wagman, who contributed research to the New Nets Project but has no connection to Royal Guard or DCT, added that cost also factors into which nets countries use in their malaria control programs. According to UNICEF’s supply division, the wholesale price of Interceptor G2 nets is $2.94 each, while the price of Royal Guard was not available and Disease Control Technologies did not provide STAT with pricing information.

The new nets are more expensive than previous versions, but the additional cost appears to be offset by public health savings. While the additional cost per case of malaria prevented was between $0.66 and $3.56, according to the New Nets Project, the total savings to health systems were close to $30 million.

“Insecticide resistance is one of the major challenges to combating malaria throughout the world,” said Conor McMeniman, assistant professor in the Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health. “Excitingly, this past year there’s been a strong recommendation for dual ingredients insecticide-treated bed nets with the purpose to break the most common mode of insecticide resistance in mosquitoes that transmit malaria in sub-Saharan Africa.”

But experts know the new nets are a limited solution, as they expect mosquitos to eventually become resistant to the second-generation bed nets. Research on other means of vector control continues to be necessary, said Wagman, as is vaccinating a larger percentage of the population against the disease.

“I am really, really happy that we now have a better bed net on the market. I think that this is a big improvement and that’s a positive development. But… at the end of the day a bed net is still a bed net and even one that is more efficacious, it’s still limited,” he said. “We’re going to reach the limits of what’s achievable with the bed nets, how effective the bed nets are at killing mosquitoes.”