Malaria Vaccine Combo Could Reduce Cases by 91%

Transmission-blocking vaccines (TBVs), and pre-erythrocytic vaccines (PEVs) prevent mosquitoes from transferring the malaria parasites

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Using two experimental anti-malarial vaccines, which work in different ways, can greatly reduce the number of malaria infections in animals, according to new research led by the Imperial College London.

These 2 experimental vaccines, which individually achieve 48 percent and 68 percent reductions in malaria cases, could achieve 91 percent reduction when combined.

Presently, each vaccine is at a different stage of human trials, and there have not been efforts to combine them.

This study, published today in the journal eLife, tested vaccines that prevent mosquitoes from transferring the parasites, called transmission-blocking vaccines (TBVs), and those that prevent the parasite from infecting the liver, termed pre-erythrocytic vaccines (PEVs).

It has been assumed that combining these vaccines would increase their efficacy, but it has never been tested until now. The team found that when a partially effective PEV was combined with the most effective transmission-blocking vaccine, the efficacy was around 91 percent.

Lead researcher Dr. Andrew Blagborough, from the Department of Life Sciences at Imperial, said in a press release, “This is the first direct evidence that combining vaccines of different types significantly improves their efficacy in terms of reducing malarial burden.”

Malaria is caused by a group of parasites that have a complex life cycle, spending time in the mosquito midgut and salivary glands, in the human liver, and circulating in the human blood, where they cause the disease.

In 2016, 44 countries reported fewer than 10,000 malaria cases, compared to 37 countries in 2010, according to the World Health Organization (WHO).

In 2016, an estimated 216 million new malaria cases and 445,000 deaths occurred, largely among children living in sub-Saharan Africa.

In the United States, approximately 1,700 cases of imported malaria occur each year, with approximately 37 percent of these cases occur in women, including 5–6 percent who are pregnant at the time they are infected.

When a woman is infected with malaria during pregnancy, they are at an increased risk for maternal and fetal complications, says the Centers for Disease Control and Prevention (CDC).

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RTS,S is the world’s first PEV malaria vaccine that has been shown to provide partial protection against malaria in young children by blocking infection of the liver.

However, its maximum efficacy is under 50 percent.

There are currently several types of transmission-blocking vaccines in early trials, which are thought to reduce the number of parasites in the mosquito salivary glands.

Their efficacy typically ranges from around 50-95 percent.

The efficacy of current lead malaria vaccines is known to reduce overtime after vaccines are administered, so the team will also investigate how combined vaccines perform in the long term.

“Malaria is a mosquito-borne disease characterized by fever, chills, and flu-like symptoms. It can cause serious complications and death if left untreated. Malaria prevention measures should be taken very seriously since there is no vaccine currently available,” said Natasha Gildersleeve, PharmD MTM Clinical Pharmacist at Brookshire Grocery Company.

“If you plan on traveling to a country where malaria is present, talk to your doctor or pharmacist well in advance about malaria prevention medications,“ Gildersleeve said.

The CDC publishes malaria maps for easy visualization of current outbreaks. 

The research was funded by the PATH Malaria Vaccine Initiative and the Medical Research Council (MRC), including researchers at Imperial MRC Centre for Outbreak Analysis and Modelling.

For more information, please contact: Hayley Dunning, Research Media Officer (Natural Sciences), email: [email protected]