WASHINGTON, Aug. 8 (Xinhua) -- An investigational vaccine has been found to offer "complete protection" against malaria infection in healthy adults in an early-stage clinical trial, U.S. researchers reported Thursday.
Although the vaccine, known as PfSPZ Vaccine, can only be administered intravenously, a rare delivery route for vaccines, it does pave the way for broadly applicable malaria prevention, researchers from the U.S. National Institute of Allergy and Infectious Diseases (NIAID) and other organizations said.
In the Phase I clinical trial described in the journal Science, volunteers received two to six intravenous doses of PfSPZ Vaccine, which consists of live but weakened sporozoites of the species Plasmodium falciparum, the most deadly of the malaria-causing parasites.
The researchers found that the higher dosages of PfSPZ Vaccine were associated with protection against malaria infection. The vaccine protected all six volunteers who received the highest doses from malaria infection. Of the 15 participants who received higher dosages of the vaccine, only three became infected, compared to 16 of 17 participants in the lower dosage group who became infected. Among the 12 participants who received no vaccine, 11 participants became infected after mosquito challenge.
"In this trial, we showed in principle that sporozoites can be developed into a malaria vaccine that confers high levels of protection," Robert Seder, chief of the Cellular Immunology Section of the NIAID Vaccine Research Center and principal investigator of the trial, said in a statement.
"These trial results are a promising first step in generating high-level protection against malaria, and they allow for future studies to optimize the dose, schedule and delivery route of the candidate vaccine," Seder added. ??The researchers said that a number of follow-up studies are planned, including research to evaluate the vaccine's different dose schedules, possible protection against other Plasmodium strains and the durability of protection.
The researchers may also evaluate whether higher doses administered subcutaneously or intradermally provide the same level of protection as that found in this study. ??There were about 219 million cases of malaria in 2010 and an estimated 660, 000 deaths. Most deaths occur among children living in Africa where a child dies every minute from malaria.
"The global burden of malaria is extraordinary and unacceptable, " said NIAID Director Anthony Fauci. "However, a vaccine has remained an elusive goal. We are encouraged by this important step forward."