Scientists discover why some Kenyans never get malaria

A mosquito that transmits the malaria-causing parasite.

They found that people who resist severe malaria often carry antibodies that recognise and attack specific proteins produced by the malaria parasite during infection.

Researchers believe these naturally developed immune responses help the body stop the disease before it becomes dangerous and could guide the development of stronger malaria vaccines.

The findings were published in the journal Nature Communications by scientists from Kenya Medical Research Institute (Kemri), Imperial College London and other international research institutions.

The proteins are made by the malaria parasite itself during the stage when it invades red blood cells.

Scientists found that some people had already developed strong antibodies against these parasite proteins after years of repeated malaria exposure, allowing their immune systems to recognise and control infection faster.

The researchers wrote: “People living in areas with a high intensity of malaria transmission gradually acquire immunity following repeated malaria infections.” They added: “This naturally acquired immunity (NAI) is characterised by an ability to control parasitaemia during the blood stage of the infection, and to prevent the clinical symptoms of malaria.”

To understand how this protection works, scientists deliberately exposed 142 healthy Kenyan adults to malaria parasites under tightly controlled medical conditions, then monitored who became sick and who stayed healthy.

They explained: “One hundred and forty-two adults were challenged with ~ 3200 sporozoites and monitored twice daily for the development of clinical symptoms and for parasitemia over 22 days. Fifty-six of one hundred and forty-two volunteers (39 per cent) met the treatment criteria before the end of the study and are hereafter referred to as non-immune.”

The remaining 86 volunteers blocked the infection naturally without requiring treatment.

Scientists then analysed blood samples collected before infection to identify which antibodies were already present in people who resisted illness.

The scientists identified six parasite proteins that repeatedly appeared among volunteers who naturally resisted severe malaria illness: MSP1, MSP11, MSP7, RAMA, PHISTB and PTEX150.

The study noted: “Two vaccines are currently licensed against Plasmodium falciparum malaria but offer only partial protection that wanes, necessitating repeated dosing that is challenging to implement where it is needed most. The World Health Organization’s preferred target for future vaccines is >90 per cent efficacy with a duration of protection of at least one year.”

The findings are reported in a paper is titled "Controlled human malaria infection in adults identify combinations of merozoite antigens associated with clinical immunity".

Kenya was among the first African countries to introduce malaria vaccination after rolling out the RTS,S vaccine pilot programme in western Kenya in 2019. The country also started using the newer R21 malaria vaccine last year, which experts say is cheaper and easier to expand nationwide.

Malaria remains one of Kenya’s deadliest infectious diseases, especially in western Kenya and the Coast region. According to the Ministry of Health, malaria incidence declined from 104 to 72 cases per 1,000 people between 2023 and 2025, and four million infections were recorded last year.

One of the study’s most important findings was that combinations of antibodies appeared to protect people better than single immune responses.

The scientists explained: “We therefore tested all possible combinations of responses to 2, 3, 4 and 5 antigens.” They added: “Protective efficacy increased with breadth, defined as the sum of individual antibody responses.”

The study further stated: “We found that none of the individuals with high responses to selected pairs or trios of antigens succumbed to malaria.” However, the researchers cautioned: “We do not suggest that these combinations would likely translate to 100% protection in the field.”

Scientists say the findings could help future vaccines mimic the natural protection already developing in some adults living in malaria-endemic regions.

Still, the researchers warned that more studies are needed before the findings can be turned into a vaccine.

The researchers wrote: “We consider these data as important first steps. Further studies would include vaccination of mice to determine functional immunity and epitope and structural level characterisation of these antigens.”