Dutch malaria vaccine delays infection, but does not yet sufficiently protect it

While hard work is being carried out worldwide on a vaccine against corona, the search for a well-functioning malaria vaccine has not stopped. Because that is still not there. The LUMC in Leiden and the Radboud university medical center in Nijmegen have been working on a vaccine against malaria for ten years. They are publishing the results of the latest study today.

The vaccine was tested on a group of healthy volunteers. Despite the vaccine, almost all vaccinated participants still found malaria in the blood. “The vaccine unfortunately does not provide the protection we had hoped for,” says Meta Roestenberg, infectiologist at LUMC and Radboud university medical center, News hour.

The scientists did see that the participants who received the vaccine developed a defense against the malaria infection, although this protection was not complete. The disease is postponed, but not prevented, says Roestenberg. “The vaccine delayed the onset of malaria for a few days.”

And that is an important result of the research and reason for the scientists to start further research into the vaccine. “We have seen that it is safe and that it generates a defense response. We now have silver, but of course we go for gold,” said the infectiologist.

The vaccine now tested contains malaria parasites that have been weakened by genetic modification. The scientists have removed certain genes from the parasites, including the gene with which the parasite can multiply in humans.

“The vaccine is a crippled parasite that cannot fully develop,” says physician-microbiologist Robert Sauerwein of Radboud university medical center. “That parasite is so slow in its development that the immune system is given time to build up a good protective immune response.”

It is a unique study, Roestenberg said in 2017 when the first human trial took place. “There has never been an experiment worldwide where malaria parasites have been genetically weakened, injected and then used to vaccinate humans.”

Stung by real mosquitoes

Nineteen volunteers participated in the first trial of the vaccine. They received one injection of attenuated malaria parasites that subsequently did not cause malaria. After this successful trial, the scientists were allowed to test the vaccine on 48 people.

These volunteers received not one, but three injections of parasites. And they were also stung by real malaria mosquitoes, which were specially bred for this purpose in a hermetically sealed laboratory in Nijmegen. More than five agencies had to authorize that plan.

The subjects were then closely monitored, Sauerwein says. “If they develop flu-like symptoms, such as a little headache or fever, we immediately give them an active anti-malaria drug. And then the parasite will be out of the blood within a day.”

Such an anti-malaria drug is not a vaccine, but a drug that can only fight an infection at an early stage. For many people in African countries, such a means is out of reach, because it is very expensive. With a vaccine, the parasites cannot cause infection at all and people are protected for life.

New version of the vaccine

The fact that no great success has now been achieved does not mean that scientists have stopped developing the vaccine. They are currently working on the next version, says Roestenberg. “We are currently preparing the study. But we can start testing the vaccine on humans in two years at the earliest.”

Because it is a new drug, the entire test process must be gone through again, says the infectiologist. “That means that we test the vaccine on a few people first, then do an initial real trial and hopefully expand it to subsequent trials with more volunteers.”

Despite the results of the research and the fact that the current focus is on the development of a corona vaccine and medicine, there is money for follow-up research, according to Roestenberg. The European Union, the Bill and Melinda Gates Foundation and a number of Dutch parties contribute to this.

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