WASHINGTON: Scientists have created harmless versions of malaria-causing parasite by applying radiation science, and are using them to create a new malaria vaccine that could be more effective than the ones already in existence.

Researchers at the National Institute of Standards and Technology (NIST) used their expertise to help Maryland-based biotech firm Sanaria Inc., which is creating the new vaccine, create these parasites.

Decades ago, scientists had discovered that volunteers built up high levels of protection to malaria after being exposed to mosquitoes containing live, radiation-weakened parasites. Since then they had been striving to use vaccines based on whole living parasites.

However, the manufacturing technology for extracting weakened parasites from their mosquito carriers has come into being in recent days only.

In the manufacturing process, live mosquitoes containing the parasite are exposed to gamma rays. To ensure that the parasites are sufficiently weakened for the vaccine, yet remain alive, they must be exposed to a radiation dose of at least 150 gray, but not much more.

The researchers have revealed that to be safe for human trials, all mosquitoes must get their minimum radiation dose of 150 gray.

NIST researchers will remain associated with the manufacturing of the vaccine by doing regularly scheduled quality-assurance tests to ensure the desired dose is being delivered to the mosquitoes.