Pharmacology Update
Tetanus Toxoid, Reduced Diphtheria Toxoid, and Acellular Pertussis Vaccine Adsorbed (Tdap) (Adacel™)
By William T. Elliott, MD, FACP, and James Chan, PhD, PharmD. Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; Associate Clinical Professor of Medicine, University of California, San Francisco; Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Drs. Chan and Elliott report no financial relationships to this field of study.
The FDA has approved a new single booster vaccine against pertussis, diphtheria, and tetanus for adolescents and adults. Aventis Pasteur Limited will market the new vaccine as Adacel™. In contrast to the combination vaccine for use in infants and children, Adacel™ contains diphtheria toxoid and one of the pertussis components (detoxified pertussis toxoid) in reduced quantities. The new vaccine is similar to Boostrix® marketed by GlaxoSmithKline which was approved only for adolescents ages 10-18 years.
Indications
Adacel™ is indicated for active booster immunization for the prevention of tetanus, diphtheria, and pertussis as a single dose in adolescents and adults (ages 11-64 years).1
Dosage
The vaccine dose is 0.5 mL given by intramuscular injection. Each injection contains 2.5 g of detoxified pertussis toxoid, 5 g of filamentous hemagglutinin, 3 g of pertactin, 5 g of fimbriae types 2 and 3, 2 Lf of diphtheria toxoid, and 5 Lf of tetanus toxoid. The injection also contains aluminum phosphate, residual formaldehyde, residual glutaraldehyde, and 2-phenoyethanol. The injection does not contain thimerosal.
Potential Advantages
This is the first vaccine for pertussis indicated for adolescents and adults. The immune responses to a single dose of Adacel were at least comparable to response in infants to DTaP.2
Potential Disadvantages
The most common adverse events were injection site reactions and fever. In adolescents the frequency of any injection site pain and fever (≥ 100.4° F) was higher in Tdap than Td (77.8% vs 71% and 5% vs 2.7%).1 In adults the frequencies of adverse events were not significantly different. As with any vaccine, administration does not result in 100% protection in vaccinated individuals.1
Comments
The approval of Tdap was based on a clinical trial comparing antibody titers of diphtheria and tetanus to Td (n = 2296 per protocol population) and pertussis to infants who received DTaP.1,2 Seroprotection, booster response rate, and geometric mean titer were comparable for diphtheria and tetanus compared to Td. Postvaccination antibody responses (geometric mean titer to pertussis antigens) were about 2-5 times higher in adults/adolescent compared to infants after 3 vaccinations. Adverse effects were generally similar to Td or DTaP.
Clinical Implications
Reports of cases of pertussis are increasing.3 Waning immunity in adolescents and adults, and the lack of a booster vaccine may be contributing factors. Pertussis causes significant morbidity as well as cost. Prolonged cough is common and complications include pneumonia (about 3%), seizures and encephalopathy (< 0.6%).3 In a prospective survey of confirmed pertussis cases, 83% of adolescents missed a mean of 5.5 days of school and 61% of adults missed 9.8 days from work.4 Medical cost in 2002 dollars were $242 and $326 dollars for adolescents and adults, respectively. Nonmedical costs were $155 and $447 respectively. Currently the tetanus and diphtheria (Td) booster is recommended for adolescents but a pertussis vaccine has not been available. The approval of two vaccines for adolescents and one for adults is expected to change current practice. A cost benefit analysis suggests that immunizing adolescents with a Tdap vaccine should provide significant health and economic benefits.5
References
1. Adacel™ Product Information. Aventis Pasteur Inc, June 2005.
2. Pichichero ME, et al. JAMA. 2005;293:3003-3311.
3. Hewlett EL, et al. N Engl J Med. 2005;352:1215-1222.
4. Lee GM, et al. Clin Infect Dis. 2004;39:1572-1580.
5. Hay JW, Ward JI. Pediatr Infect Dis J. 2005;24(6 Suppl):S127-S133.
The FDA has approved a new single booster vaccine against pertussis, diphtheria, and tetanus for adolescents and adults. Aventis Pasteur Limited will market the new vaccine as Adacel. In contrast to the combination vaccine for use in infants and children, Adacel contains diphtheria toxoid and one of the pertussis components (detoxified pertussis toxoid) in reduced quantities. The new vaccine is similar to Boostrix® marketed by GlaxoSmithKline which was approved only for adolescents ages 10-18 yearsYou have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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