New whooping cough vaccine for adolescents and adults

In the first study of its kind, researchers at Saint Louis University have demonstrated that immunization with a new vaccine could potentially prevent more than a million cases of pertussis (whooping cough) each year in adolescents and adults.

Most children are protected from pertussis by a series of vaccines in early childhood. But the vaccine protection wanes after a decade or so, leaving adolescents and adults susceptible to the bacterial infection.

"It's a misconception that you're protected from pertussis for life if you've been vaccinated as a child," said Stephen J. Barenkamp, M.D., professor of pediatrics and one of the study's clinical investigators. He also is director of the Pediatric Research Institute at the Saint Louis University School of Medicine. "The study demonstrated that an estimated one in 300 adolescents and adults contracts the illness each year. The results also demonstrate that an effective vaccine is now available for this population and its use should be strongly encouraged."

Barenkamp's comments are based on results of a large, multi-center clinical study of more than 2,781 healthy adolescents and adults between the ages of 15 and 65. Barenkamp said approximately half the patients received a vaccine to protect against pertussis. The other half received a control vaccine. Researchers followed the patients for 2.5 years and determined that the pertussis vaccine was more than 90 percent effective in preventing the highly contagious illness.

Although pertussis is rarely life-threatening in adults, Barenkamp said the booster shot would not only prevent weeks of severe coughing, it hopefully would also prevent adults from spreading the infection to small children, for whom the disease can be deadly.

The Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recently recommended that all 11 and 12 year olds be given a dose of this new pertussis vaccine as a combined formulation with tetanus and diphtheria boosters.

Recommendations for immunization of older adults are under active review.

Barenkamp said another purpose of the study was to gather data on the true incidence of pertussis in adolescents and adults.

He said that underreporting of the illness is substantial because physicians often do not consider the possibility of pertussis when they treat adults for persistent cough. Complicating matters further, he said, the test used to detect pertussis in children is often not sensitive enough to detect pertussis in adults. Barenkamp said a test used during the study known as the pertussis polymerase chain reaction (PCR) assay is more sensitive and is becoming more widely available for testing of patients of all ages.

Study results were published in the October 13, 2005 issue of the New England Journal of Medicine.

Other institutions that participated in the study include: the UCLA Center for Vaccine Research; University of Rochester; University of Pittsburgh School of Medicine; Children's Hospital of Pittsburgh; Baylor College of Medicine; Cincinnati Children's Hospital Medical Center; University of Maryland School of Medicine; Vanderbilt University Medical Center; and the National Institute of Allergy and Infectious Diseases at the National Institutes of Health.