Two safer new vaccines against whooping cough could prevent up to 1 million cases among U.S. teenagers and adults each year and keep them from infecting children, who can die from the illness, a government study found.
The vaccine, tested on nearly 2,800 people ages 15 to 65, proved 92 percent effective in preventing infection with the highly contagious germ.
Whooping cough, or pertussis, can cause weeks of misery and coughing so severe it cracks ribs. The bacterial disease can kill children, particularly unvaccinated babies.
Cases of whooping cough dramatically declined over the past half-century because most children get several shots against it by age 6. However, immunity wears off over time, and outbreaks among U.S. adults and teenagers began rising sharply during the 1990s.
According to the National Partnership for Immunization, teens and adults now account for about 60 percent of whooping cough cases.
Last spring, the Food and Drug Administration approved two new booster vaccines: Boostrix, made by GlaxoSmithKline, is for 10- to 18-year-olds, and Adacel, from Sanofi-Aventis, is for people 11 to 64; both include boosters against diphtheria and tetanus.
The pertussis portion of those vaccines is identical or similar to the shot used in the study. The new vaccines use purified parts of the pertussis bacterium to build up patients' immunity. Older vaccines contain the whole germ and are more likely to cause side effects, including fever, jitters, drowsiness and loss of appetite.
The study was reported in Thursday's New England Journal of Medicine.
Students, health-care workers and other volunteers at eight U.S. medical centers got the pertussis vaccine or, in the half serving as a comparison group, a hepatitis A vaccine. They were followed closely through the late 1990s for 22 months on average.
Just one person in the pertussis vaccine group became infected. Nine in the comparison group were infected.
The researchers estimated there are 1 million U.S. cases of pertussis each year among people 15 and older. But most of those cases go undiagnosed.
In an accompanying editorial, Dr. Scott A. Halperin of Dalhousie University in Halifax, Canada, but said more research is needed on the vaccine's use in pregnant women and the elderly.
The study was supported by the National Institutes of Health under an agreement with GlaxoSmithKline.