Acellular Pertussis Vaccine Proves Effective In Adults, Adolescents

"During the 1990s, the number of reported pertussis cases amongadolescents and adults more than doubled in the United States as theprotective effects of earlier childhood immunizations have waned," saysAnthony S. Fauci, M.D., director of the National Institute of Allergyand Infectious Diseases (NIAID), National Institutes of Health, whichfunded the study. "This new study shows that an effective adultacellular pertussis vaccine is feasible and if routinely used couldprovide the U.S. population greater protection against the disease."

Known as the Adult Pertussis Trial, the 2.5-year study involved 2,781healthy individuals between 15 and 65 years of age. Volunteers wererandomly assigned to one of two similarly sized groups that receivedeither the acellular pertussis vaccine or the control hepatitis Avaccine (Havrix). For purposes of the trial, pertussis cases weredefined as illnesses with a cough lasting at least five days thatoccurred more than 28 days after vaccination and were confirmed throughblood and nasal mucus testing.

Joel I. Ward, M.D., of the Center for Vaccine Research at theUniversity of California, Los Angeles, led the multicenter clinicalstudy. GlaxoSmithKline, based in Philadelphia, supplied both thepertussis test vaccine and the hepatitis A vaccine.

Ten confirmed cases of pertussis occurred during the trial--nine caseswere among the individuals who received the hepatitis A vaccine. Theresearchers concluded that a single dose of the test vaccine was safeand 92 percent effective in protecting adolescents and adults againstpertussis.

Although infants are routinely inoculated against pertussisthrough a series of three diphtheria-tetanus-acellular pertussis (DTaP)vaccines given in the first year of life, immunity has been shown toweaken after six to 10 years.

"The purpose of an adult pertussis vaccine is to prevent the disease inadults with the added benefit that it may help to put up a roadblock inthe transmission of the disease, so that parents, grandparents andother adults are not unknowingly passing the disease along," says DavidKlein, Ph.D., of NIAID's Respiratory Diseases Branch.

In 2004, the highest number of U.S. pertussis cases was amongindividuals 10 to 18 years of age with roughly 6,500 cases reported,according to data from the Centers for Disease Control and Prevention.Infants less than six months old experienced the second highest numberof pertussis cases last year, with an estimated 2,200 cases reported.

NIAID is a component of the National Institutes of Health, an agency ofthe U.S. Department of Health and Human Services. NIAID supports basicand applied research to prevent, diagnose and treat infectious diseasessuch as HIV/AIDS and other sexually transmitted infections, influenza,tuberculosis, malaria and illness from potential agents ofbioterrorism. NIAID also supports research on transplantation andimmune-related illnesses, including autoimmune disorders, asthma andallergies.

Reference: JI Ward et al. Efficacy of an acellular pertussisvaccine among adolescents and adults. The New England Journal ofMedicine 353(15):1555-1563 (2005).<