NextBillion - An Initiative of the William Davidson Institute at the University of Michigan

Thursday, July 31, 2014

A “pretty good” malaria vaccine is on track to be the first to market.

It only prevents infection about one-quarter to one-half the time, so it’s not as good as most vaccines. But for a disease like malaria, which kills 600,000 people a year, “pretty good” may be good enough.

GlaxoSmithKline has applied for regulatory approval for its RTS,S vaccine.

Partial protection

A new 18-month study in the journal PLoS Medicine shows the vaccine prevented 46 percent of malaria illnesses in children five to 17 months old and 34 percent of severe cases, the kind most likely to kill.

“It’s a pretty good vaccine,” said medical epidemiologist Mary Hamel of the U.S. Centers for Disease Control and Prevention and one of the authors of the new study. “We were looking for 30 percent or higher.”

Most vaccines against childhood illnesses are 80-90 percent effective or better. But, she said, “the burden of malaria is so high across sub-Saharan Africa that even with modest efficacy numbers like these, you can get a pretty high impact.”

Multiple illnesses per year

For example, Hamel says children contracted malaria an average of five times per year each at the western Kenyan study site where she worked. At that location, for every 1,000 children who got the shots, the vaccine prevented about 2,400 cases of malaria, and 40 severe cases.

The study found the vaccine was less effective in infants six to 12 weeks old. It prevented 27 percent of illnesses but had no impact on severe cases.

And the vaccine lost much of its punch “more rapidly than one would hope” over the course of the 18-month study, Hamel said. One of the next steps is to see if a booster shot can improve long-term efficacy.