FDA Approves Expanded Age Indication for Tdap Booster Vaccine

Laurie Barclay, MD

April 20, 2009

April 20, 2009 — The tetanus toxoid/reduced diphtheria toxoid/acellular pertussis single-dose booster vaccine (Tdap; Boostrix, GlaxoSmithKline Biologicals) was approved for an expanded age indication (10 – 64 years) by the US Food and Drug Administration (FDA), on December 4, 2008, according to an article published in the April 17 issue of the Morbidity and Mortality Weekly Report. The vaccine was initially licensed only for persons aged 10 to 18 years.

"For prevention of tetanus, diphtheria, and pertussis, adolescents and adults are recommended to receive a one-time booster dose of Tdap," the report states. "Adolescents aged 11–18 years who have completed the recommended childhood diphtheria and tetanus toxoids and pertussis vaccine[/diphtheria and tetanus toxoids and acellular pertussis] vaccination series should receive a single dose of Tdap instead of tetanus and diphtheria toxoids (Td) vaccine, preferably at a preventive care visit at age 11 or 12 years. For adults aged 19–64 years who previously have not received a dose of Tdap, a single dose of Tdap should replace a single decennial Td booster dose."

Current doses of the booster vaccine in stock can now be used for persons aged 10 to 64 years. However, the safety and efficacy of Tdap have not been established in pregnant women, nursing mothers, and children younger than 10 years.

On October 23, 2008, the Advisory Committee on Immunization Practices was notified of the impending expanded age indication for Boostrix and reviewed data from 2 US clinical trials on the safety and immunogenicity of Boostrix in adults aged 19 to 64 years.

The safety and reactogenicity profiles of Boostrix in both trials resembled those of Adacel (Sanofi Pasteur), another Tdap vaccine licensed for use in adults. Immune responses to Boostrix for diphtheria and tetanus were noninferior to those of Adacel.

Boostrix contains the same 3 pertussis antigens as Infanrix (GlaxoSmithKline Biologicals), but in lower quantities. In the first clinical trial, pertussis antibody concentrations for pertussis toxoid (PT), filamentous hemagglutinin (FHA), and pertactin were noninferior to those of infants after a primary diphtheria and tetanus toxoids and acellular pertussis vaccination series with Infanrix.

In the second trial, seroresponse to Boostrix and influenza vaccine Fluarix (GlaxoSmithKline Biologicals), given together or separately, were noninferior for diphtheria, tetanus, PT, and influenza, and noninferiority criteria were marginally exceeded for FHA and pertactin responses.

"Boostrix is now indicated for use as a single-dose booster immunization in persons aged 10–64 years," the report concludes. "The recommended interval between 2 doses of Td-containing vaccines in adolescents and adults is at least 5 years because of concern over increased reactogenicity; however, data are available suggesting that intervals as short as approximately 2 years are safe. An interval <5 years between Td and Tdap may be used if increased risk for acquiring pertussis (e.g., during outbreaks or periods of increased pertussis activity in the community, or among health-care workers) exists."

Morb Mortal Wkly Rep. 2009;58:374–375.

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