Malaria vaccine ‘offers safe, effective protection for more than 1 year’

THERE is currently no vaccine for malaria, but with almost half of the world’s population at risk for the disease, there is a desperate need for one. Now, researchers believe they may be well on their way to fulfilling this need. Published the journal Nature Medicine, the results from a phase I clinical trial reveal that a vaccine called PfSPZ protected healthy adults against malaria for more than 1 year.
Malaria is a disease most commonly transmitted through the bite of an infected Anopheles mosquito. Symptoms of malaria include fever, flu-like illness, headache, shaking chills, muscle aches, and nausea and vomiting. It can also cause anemia, jaundice, and – if not treated promptly – seizures, kidney failure, coma, mental confusion, and death.
According to the World Health Organization (WHO), there were around 214 million cases of malaria across the globe last year and around 438,000 deaths from the disease. Plasmodium falciparum is the malaria parasite most likely to cause severe, life-threatening disease. In the new study, principal investigator Dr. Robert A. Seder, of the National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Center, and colleagues reveal how the PfSPZ vaccine achieves long-term protection against P. falciparum.
The PfSPZ vaccine consists of live, weakened P. falciparum sporozoites, which are immature forms of the parasite. In previous research, Dr. Seder and colleagues found that the vaccine was highly protective against P. falciparum for 3 weeks following immunization. For this latest research, the team set out to investigate whether the vaccine would offer longer-term protection.
The researchers gave the vaccine to 57 healthy adults aged 18-45 years with no history of malaria. A further 32 healthy, age-matched adults without a history of malaria were enrolled but were not vaccinated, serving as controls. The team divided the vaccine recipients into groups in order to determine the optimal dosage, number of vaccinations, and administration route for the most effective protection.
Some of the vaccinated participants received three intravenous (IV) immunizations, while others received four IV immunizations – all at higher doses than had been previously tested in humans. Some of the vaccinated participants received four immunizations through intramuscular injection (IM) at a dose tenfold higher than the IV dose. The team assessed both short- and long-term protection against malaria in this study.
In order to assess short-term protection, all participants were exposed to the bites of mosquitoes infected with P. falciparum 3 weeks after their last immunization. On assessing the blood samples of participants, the researchers found that three of nine subjects who received three IV doses of the PfSPZ vaccine had no detectable parasites in their blood, meaning they were protected against malaria.

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