The first vaccine against group A strep to be tested on people in 30 years appears safe and protective against the bacteria that causes strep throat, rheumatic fever and other diseases.
But scientists reporting in today's Journal of the American Medical Association caution that the results of a small clinical study are preliminary and that a usable vaccine is still many years away.
The need for such a vaccine is greatest in developing countries, where rheumatic heart disease, a complication of strep A infection, is still common, says lead researcher Karen Kotloff of the University of Maryland. In the USA, rheumatic fever is much rarer, but strep A infections can cause more serious diseases, including a form of pneumonia that killed Muppets mastermind Jim Henson in 1990.
In the study, Kotloff and colleagues injected 28 volunteers with a genetically engineered vaccine made with fragments of a protein from the strep A bacterium. Follow-up blood tests showed the vaccine boosted antibodies to strep A, indicating protection against the bug.
A major hurdle to development of a strep vaccine has been the danger that the antibodies prompted by the vaccine could attack a protein in the heart that is similar to a strep protein. That would raise the risk that the vaccine itself could cause rheumatic heart disease. To overcome this, Kotloff says, researchers selected only segments of the strep A's protein that prompt immunity. The result: ''We had immune responses we were happy with, and there were no safety issues,'' she says.
Researchers have been trying to create a strep A vaccine since the 1930s, and several are now in experimental stages, says Michael Pichichero of the University of Rochester, who wrote an accompanying editorial. The new study is promising, he says, but too small to detect dangerous side effects.
''It's a preliminary report, but a positive step in a long journey ahead,'' he says. ''If you're going to move ahead with a vaccine like this, you're going to have to move cautiously.''
He says the Food and Drug Administration may require testing on up to 60,000 people to ensure that rare side effects don't emerge. Such extensive testing would be very expensive and may cause drug companies to back away, he says.
Infectious-disease specialist William Schaffner of Vanderbilt University in Nashville, who was not involved in the study, says that ''this is a highly refined new approach to the development of a streptococcal vaccine'' and that the results ''are good enough to encourage people to go on'' to larger studies.
In another study in today's journal, researchers at the Centers for Disease Control and Prevention report that a single dose of chickenpox vaccine is about 80% effective in preventing the disease, but when vaccinated people do erupt in spots, the disease is usually mild, and they're half as likely as unvaccinated people to spread it to others.
The findings suggest that a chickenpox booster shot may be needed if the goal of elimination of the disease is to be met, researchers say.
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