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July 29, 2014

'Pretty Good' Malaria Vaccine Moves Forward

by Steve Baragona

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.

No 'silver bullet'

Still, many experts say it is an important step forward. “We don’t really have a silver bullet,” said Dr. Chris Plowe at the University of Maryland School of Medicine.

“This is a first-generation vaccine,” he added. “We’d all like to see a vaccine that has 100 percent protective efficacy, but in the context of other tools and how we expect to do with a really tough disease like malaria, this is actually pretty good and reason for some celebration, I would say.”

“There’s not a single licensed, efficacious vaccine for any human parasitic infection on the planet,” noted Dr. Jonathan Kurtis at Brown University.

But he said there will be questions about whether a vaccine that prevents relatively few deaths will be worth the cost.

“Who is going to pay to deliver this vaccine, which is not a cheap vaccine to manufacture?” he asked. “Will they pay to stop 20 cases per 1000 participants per year and a half? I can’t answer that.”

Tulane University vaccine expert Nirbhay Kumar worries the vaccine will raise hopes beyond what it can deliver.

“While we expect there will be some benefit from deploying this vaccine, I think having high expectations and not fulfilling those expectations might do more damage than the benefit that we could see,” he said.

GlaxoSmithKline has not disclosed what the price of the vaccine will be, but it says it will cover the cost of manufacturing plus 5 percent, which will be re-invested in vaccine research.

The company has submitted the vaccine to European regulators for approval, which could come by the end of next year.

'A good start'

The goal set by the health nonprofit organization PATH and other major international donors calls for a vaccine that is 50 percent effective against severe disease and death in the first 12 months. The GlaxoSmithKline vaccine met that goal for older children but not infants in an earlier study.

There is “still a lot to learn before we decide exactly how it’s going to be introduced,” according to PATH vice president for product development David Kaslow. And, he added, those decisions will ultimately be up to the affected countries themselves.

PATH is also supporting other research efforts, but none is as close to approval as this one.

“For the foreseeable future, this is what we have,” Kaslow said. “Is it perfect? No. But is it a good start? Yes.”