Experimental Malaria Vaccine Shows Promise for Longer Protection

Researchers find volunteers who were vaccinated with PfSPZ had no detectable parasites in their blood for more than 1 year.



Results of a phase 1 trial for an experimental malaria vaccine showed that the vaccine protected against infection for more than 1 year, according to the NIH. The PfSPZ vaccine is composed of attenuated sporozoites of Plasmodium falciparum, a malaria-causing parasite. Sanaria Inc. developed and produced the vaccine with funding from the National Institute of Allergy and Infectious Diseases.

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Earlier research found that the vaccine was “highly protective” 3 weeks after immunization; however, researchers at the NIH Clinical Center in Bethesda and the University of Maryland Medical Center wanted to find out whether this protection could last 5 months to 1 year. The researchers vaccinated 59 healthy volunteers who had never had malaria, and 32 participants did not receive a vaccination. Study participants were divided into groups to assess the roles of the route of administration (IV vs intramuscular), dose, and number of immunizations.

Six of 11 people who received 4 immunizations with 2.7 x 105 PfSPZ and were exposed to bites 21 weeks after the final vaccination had no detectable parasites in their blood. Five were still infection free at 59 weeks. In those people, the vaccine seemed to confer “sterile protection,” according to the researchers. “They were protected against disease and could not transmit infection.”

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The researchers say antibodies may play a role in malaria protection early after the final immunization, but inducing T cells in the liver is likely necessary for durable protection. They suggest higher doses may further enhance protection.

Ishizuka AS, Lyke KE, DeZure A, et al [published ahead of print May 9, 2016]. Nat Med. doi: 10.1038/nm.4110.

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