By DONALD G. McNEIL Jr.

Published: August 12, 2013

A new type of malaria vaccine gave 100 percent protection against infection to a small number of volunteers in recent tests — but under conditions that would be nearly impossible to reproduce in the countries where most malaria victims live.

Health Guide: Malaria

The vaccine, made by Sanaria, a Maryland company, protected six volunteers who each got five doses over 20 weeks, according to a studypublished last week in Science.

But the vaccine is expensive to make and difficult to administer, and it is not yet clear how long the protection lasts.

“This is a scientific advance rather than a practical one,” said Dr. William Schaffner, the head of preventive medicine at Vanderbilt University’s medical school. “But any vaccine that provides even a glimmer of hope opens a door, so we have to pursue it.”

Sanaria’s vaccine is made by irradiating mosquitoes that have fed on malaria-infected blood and removing their salivary glands by hand. The radiation-weakened parasites in the saliva are then purified.

In earlier trials, the vaccine failed when injected into the skin, so this time researchers from the Army, Navy and National Institutes of Health gave it by IV drip. Six volunteers who got five intravenous doses did not get malaria when bitten by infected mosquitoes. Six of nine volunteers who got four doses were protected.

Because the vaccine is made in small batches by hand, it is impractical for poor countries, where malaria sickens more than 200 million people a year and kills about 660,000, most of them infants and pregnant women.

Giving multiple IV doses of any vaccine is also impractical because it requires sterile conditions, trained medical personnel and follow-up. IV drips are particularly hard to administer to children. “They’ve been known to squirm,” Dr. Schaffner noted.

The initial target markets for the vaccine are the military and wealthy travelers.