Exposure to malaria might significantly lower the incidence of severe Covid-19, hospitalization, and death.

These are the findings from new research undertaken in Uganda and Mali and presented at the American Society of Tropical Medicine and Hygiene annual meeting last week.

The study found low levels of severe Covid-19 symptoms among people exposed to SARS-CoV-2, the virus that causes Covid-19, in areas with high malaria burdens.

The findings have led researchers to hypothesize that previous malaria exposure could offer its survivors a reliable shield against Covid-19.

Severe cases of Covid-19 are often associated with a surge of proteins called cytokines that cause an inflammatory response and tissue damage.

The researchers in Uganda found that Covid-19 patients with a history of malaria infections, as measured by antigen levels in the body, had lower levels of cytokines. 

“All of the patients, who were categorized as having a high exposure to malaria in the past, had lower levels of the cytokines, across the board, for the different cytokines we measured, in comparison to those who had low previous exposure to malaria,” Dr Jane Achan, senior research advisor at the Malaria Consortium, a UK-based not-for-profit organization, and a co-author of the study told Devex.

This was based on a study of nearly 600 COVID-19 patients, looking at whether they were currently or previously exposed to malaria infection.

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Only 5 percent of these patients with high levels of previous exposure to malaria developed severe cases of the disease or death, as opposed to about 30 percent of those with lower levels of previous malaria exposure.

“We went into this project thinking we would see a higher rate of negative outcomes in people with a history of malaria infections because that’s what was seen in patients co-infected with malaria and Ebola,” wrote Dr Achan in a press release. “We were actually quite surprised to see the opposite- that malaria may have a protective effect.”

Dr Achan said this effect, where cytokines don't spike in the bodies of people with previous malaria exposure, has already been documented before the pandemic in older children and adults living in parts of Africa with a high prevalence of malaria.

Another study presented at the meeting found that despite widespread infection of SARS-CoV-2 in Mali, severe disease, hospitalization, and death were rare.

The researchers, from the United States National Institute of Allergy and Infectious Diseases and the Malaria Research Training Center in Bamako, Mali, conducted seroprevalence surveys of over 3,500 people in four communities in Mali’s capital, Bamako, and its surrounding areas, as well as documenting their symptoms, according to Dr John Woodford, a malaria researcher at NIAID and co-author of the study.

As of January 2021, about 59 percent of community members had been exposed to the SARS-CoV-2 virus, but this high level of exposure was not accompanied by a large influx of people into health centers.

Some of these communities had not reported any COVID-19 cases throughout the pandemic.

The COVID-19 attributable symptoms people reported weren’t substantially higher than the typical rates of illness experienced in the communities.

In fact, the number of hospitalizations and deaths were lower than those for age-adjusted US rates of severe disease — to account for the fact that, as much of the rest of sub-Saharan Africa, the population of Mali is relatively young.

“It's not that we're not seeing any markers of disease severity, it is that the rates of reporting of hospitalizations, symptomatic illness, and death are lower than would be expected. Sometimes, several-fold lower,” Dr Woodford said.

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