Pneumonia Vaccine Shows Additional Promise
It's particularly valuable for HIV-infected children
WEDNESDAY, Oct. 1, 2003 (HealthDayNews) -- An advanced version of an American-developed pneumonia vaccine for children has been successful in a South African trial.
That success has positive implications for the United States as well as the rest of the world, particularly for HIV-infected children because they're susceptible to pneumonia. Also, the vaccine shows promise in protecting against antibiotic-resistant strains of the Streptococcus pneumoniae germ, the researchers say.
The vaccine used in the African trial is similar to the Prevnar vaccine approved for use in the United States in 2000, with one important difference: It protects against nine strains of S. pneumoniae. The American vaccine protects against seven strains, which were responsible for 700 cases of meningitis and 5 million ear infections in American children before the vaccine's introduction. The vaccine has reduced infections by 69 percent, the researchers say.
In the African trial, the nine-strain vaccine reduced the incidence of first pneumonia infections by 83 percent among the 19,922 children who received it, says a report in the Oct. 2 issue of the New England Journal of Medicine.
That reduction isn't particularly important for the United States, since the two extra strains in the new vaccine are not common in this country, says study author Dr. Keith P. Klugman, a professor of international health at the Rollins School of Public Health at Emory University.
But two other aspects of the trial are of great interest here, he says.
One is that the vaccine was very successful when given to children infected with HIV, the virus that causes AIDS.
"HIV is now the leading risk factor for pneumococcal infection, so demonstrating its effectiveness is important for the United States, where Prevnar is currently indicated for HIV-infected children on the basis of expert opinion alone," Klugman says. "This is the first scientific evidence that it will work in HIV-infected children."
Perhaps more important, the trial also found a substantial reduction in the number of infections caused by antibiotic-resistant strains of the microbe, Klugman says.
"We show a 67 percent reduction in penicillin-resistant strains and a 56 percent reduction in strains resistant to trimethoprin and sulfamethoxazole," he says.
While the vaccine in the trial does differ from that used in the United States, the effect on antibiotic resistance "can be extrapolated directly to Prevnar," Klugman says.
Prevnar currently is approved only for children in the United States. Only an older, less effective pneumonia vaccine is approved for use in high-risk adults, such as elderly people with serious medical conditions. That might change, says Peter Paradiso, vice president for scientific affairs and research strategy at Wyeth Pharmaceuticals, which markets the vaccine.
"We are interested in studying Prevnar in the adult and elderly population to determine whether the responses to the vaccine would be sufficient to make it an alternative to the currently available vaccine," Paradiso says.
Prevnar is expensive. At $260 for the four-shot series, it costs more than all other recommended childhood vaccines combined. But "all children should get it," Klugman says. "Our hope is that as additional vaccines are tested, the cost may be reduced."
Dr. Kathryn M. Edwards, author of an accompanying editorial in the journal, says those expectations for the vaccine apply both globally and within the United States.
Globally, the hope is that charitable foundations and governments will overcome "the major hurdle, the ability for poor countries to buy it. Those children should have it," says Edwards, a professor of pediatrics at Vanderbilt University.
In the United States, the effectiveness of the vaccine for older people "needs to be looked at very carefully," she says. "There are certain similarities for the same kinds of infections in very little children and old people. The finding that it works so well in children indicates that it might work as well in the elderly."