June 2, 2005

Booster Vaccine for Adolescents and Adults that Includes Protection Against Pertussis Shows Promise

A new combination vaccine not yet on the market appears to provide a booster for immunity against tetanus, diphtheria, and pertussis for adolescents and adults and was found to have a similar overall safety profile when compared to the current licensed tetanus-diphtheria vaccine, according to a new study in JAMA. The article was released online today because of its public health implications and will be published in the June 22/29 print issue of JAMA.

According to background information provided by the authors, preliminary data from the Centers for Disease Control and Prevention (CDC) for 2004 show an increase in the number of pertussis cases in the U.S. to 18,957 cases from 11,647 cases in 2003. In 2004, for the first time in the United States there were more cases of whooping cough reported to the CDC in adolescents and adults than in infants. Pertussis, also known as whooping cough, is a respiratory disease. "Incompletely immunized infants and toddlers have the highest susceptibility to pertussis, the most severe disease manifestations, and highest risk of mortality (death)," the authors write. "Because no booster pertussis vaccine is currently available for adolescents or adults, these persons become increasingly vulnerable to the disease." The authors add: "Vaccination of adolescents and adults with acellular pertussis vaccines might reduce both the morbidity (complications) associated with the disease in these populations and transmission to their household and other contacts, especially infants."

Michael E. Pichichero, M.D., from the University of Rochester Medical Center, Rochester, N.Y., and colleagues conducted a randomized double-blind, comparative trial testing the licensed tetanus-diphtheria vaccine (Td) and the combination tetanus-diptheria-5-component acellular pertussis vaccine (Tdap) in 4,480 adolescents and adults from August 2001 to August 2002 at 39 U.S. clinical centers. Of these participants, 2,053 were adolescents: 1,213 received Tdap and 815 received Td. In the adult group, 2,427 were enrolled: 1,804 received Tdap and 599 received Td.

"This Tdap vaccine elicited robust immune responses in adolescents and adults to pertussis, tetanus, and diphtheria antigens, while exhibiting an overall safety profile similar to that of a licensed Td vaccine," the authors found. "These data support the potential use of this Tdap vaccine in adolescents and adults." The authors write that the "potential benefits of wide-spread use of an adolescent and adult pertussis booster vaccine include a reduction in pertussis disease." The authors continue, "Waning immunity to pertussis has been demonstrated in adolescents and adults, indicating increased susceptibility to disease in these age groups. Increased incidence of disease in older patients is of public health significance because they serve as the reservoir for Bordetella pertussis infections in infants who are too young to have completed the primary series of immunization. Pertussis may be severe and even life threatening in very young infants."

"Booster vaccination with tetanus and diphtheria toxoids every 10 years has become a standard of care in the United States. Our data indicate that the Tdap vaccine studied could be used to provide protection for tetanus and diphtheria, as recommended, while providing additional protection against pertussis," the authors suggest. "The introduction of adolescent and adult Tdap booster immunization in the United States could enhance immunity against pertussis, which would be anticipated to decrease the incidence of pertussis in the population, reduce the reservoir of pertussis, and lessen transmission from adolescents and adults to infants," the authors conclude.

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