HEALTH - MALARIA: Vaccine Test In West Africa Shows Promise
An experimental malaria vaccine achieved "limited success" in a field
trial in West Africa, researchers said yesterday, "fueling cautious hopes
that people can one day be inoculated against one of the planet's most
prolific killers," reports the Baltimore Sun.
The vaccine briefly reduced malaria cases by almost two-thirds in a
group of some 300 volunteers in Gambia last year, researchers said. After
two months, almost two-thirds were protected against infection, but that
rate fell to just 16% after 15 weeks -- too short a time for a practical
vaccine.
The vaccine, developed by the Walter Reed Army Institute of Research
and SmithKline Beecham, protected about half the volunteers in a series of
small-scale trials in the institute's Washington labs over the past three
years. But the African trial tested the vaccine against different strains of
the malaria parasite in an area of intense transmission, the Sun reports.
The vaccine consists of a piece of the malaria parasite linked to a
piece of the hepatitis B virus and mixed with a cocktail of compounds called
adjuvants, meant to boost the response of the immune system. Like all
vaccines, the Walter Reed-SmithKline product is designed to teach the immune
system to respond quickly and aggressively to a particular microbe.
At a meeting of the American Society of Tropical Medicine and Hygiene
yesterday in Baltimore, researchers cautioned that the vaccine isn't ready
for clinical use. "The Gambia trial confirmed the good and bad things about
the vaccine," said Dr. W. Ripley Ballou, who until recently led the Walter
Reed effort. "Yes, it confers immunity on about half the people it's given
to. But it lasts only a couple of months. Nobody believes that we have a
vaccine that is ready for licensing or that will meet sub-Saharan Africa's
needs."
Still, Ballou and others hope that the product, called RTS,S, can
become the foundation of a practical vaccine.
"I think it's a great step forward," said Dr. Philip K. Russell of the
Center for Immunization Research at the Johns Hopkins School of Public
Health. "We've got, for the first time, protection against malaria in the
wild, even if it's only short-term."
Malaria is common throughout the tropics -- especially among the rural
poor. It ranks with tuberculosis and AIDS as one of the biggest killers
among infectious diseases. The World Health Organization estimates that each
year the mosquito-borne parasite causes half a billion cases of clinical
illness and 1 million to 2 million deaths (Douglas Birch, Baltimore Sun, 30
Nov).
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