Background

Two Tdap vaccines are licensed for use in the United States. Boostrix (GlaxoSmithKline) is approved for a single dose in persons aged≥ 10 years; Adacel (Sanofi Pasteur) is approved for persons aged 10–64 years. Since 2005, a single booster dose of Tdap has been recommended for children and adolescents aged 11–18 years and adults aged 19–64 years (1, 2) to increase protection against tetanus, diphtheria, and pertussis. Booster doses of Td have been recommended every 10 years (decennial vaccination) to ensure continued protection against tetanus and diphtheria. These recommendations were expanded to include a single dose of Tdap for adults aged≥ 65 years in 2012 (although only one Tdap product is approved for use in persons aged≥ 65 years, either vaccine administered to a person aged≥ 65 years is considered valid)(4). Pregnant women are recommended to receive a dose of Tdap during each pregnancy to prevent pertussis in infants too young for routine vaccination (off-label use*)(3). If a tetanus toxoid–containing vaccine is indicated for wound management, Td has been recommended for nonpregnant persons aged≥ 7 years who had previously received Tdap. For pregnant women, Tdap is recommended in this setting. For previously unvaccinated persons aged≥ 7 years, a 3-dose catch-up immunization schedule included only 1 dose of Tdap, preferably as the first dose in the series (off-label use in children aged 7–9 years), and 2 subsequent Td doses at specified intervals (5). No further doses of Tdap were routinely recommended, with two exceptions: pregnant women should receive Tdap during each pregnancy (off-label use), and children aged 7–10 years who received Tdap as part of the catch-up schedule were recommended to receive the routine adolescent Tdap booster dose at age 11–12 years (1, 2). In 2010, ACIP evaluated the safety of administering Tdap at intervals< 5 years after Td administration (6, 7) and recommended that the dose of Tdap, when indicated, should not be delayed and should be administered regardless of the interval since the last tetanus or diphtheria toxoid–containing vaccine.