Malaria Vaccine Candidate Shows Promise in Early Trial

An early-stage malaria vaccine has shown promising results, especially in children and infants.

Researchers at the University of Oxford, in England, and the Ifakara Health Institute, in Tanzania, recently tested a malaria vaccine in adults, children, and infants in the East African nation, where the parasitic disease is endemic. 

Currently, there is only one other vaccine that protects against malaria, however, it is estimated that it only reduces cases of severe malaria by 30%, making the hunt for a more effective shot a priority.

The World Health Organization (WHO) estimates that there were 247 million cases and 610,000 deaths of malaria in 2021. While the parasitic disease has largely vanished from the United States, officials sounded alarms earlier this summer when eight domestic-borne cases were detected across Florida and Texas.

The parasite that causes malaria is spread through mosquito bites. It requires a specific protein, called RH5, to infect human red blood cells. The experimental vaccine series uses two injections of harmless viruses, not the malaria parasite itself, engineered to expose the immune system to the protein, teaching it to recognize it should it ever be encountered. 

In this study, published Friday in the journal Cell Med, researchers used a “prime-boost” technique, which involves giving participants a primary dose, then boosting eight weeks later with a second dose.

Participants were from three major age groups: healthy adults aged 18 to 25, young children aged 1 to 6 years, and infants aged 6 to 11 months. They were either given the experimental vaccine series or a control vaccine, in this case, a rabies vaccine. 

In total, 39 participants were primed and boosted with the experimental vaccine, and 21 participants received two doses of the control vaccine. The vaccine was deemed to be safe and tolerable in trial participants; reaching its main goal. The most common side effects were pain at the injection site and a mild fever. 

After the participants received the vaccine, researchers sampled blood from them containing antibodies that the vaccine prompted their immune systems to produce, then tested to see if these antibodies could inhibit the growth of the malaria-causing parasite. In these tests, blood sampled from the infants was the best at neutralizing the parasite, followed by children and then adults. 

The researchers say it’s unclear why infants were able to produce more antibodies, but they note that high levels of antibodies are necessary to protect against malaria, and that they will continue to focus efforts in this age group. The next steps are moving onto a phase 2 trial to see if the vaccine can actually protect against malaria infection.