Outcomes/Effectiveness Research

Pertussis vaccination in adults can be cost-effective depending on incidence rates

The incidence of pertussis, commonly known as whooping cough, has steadily increased in the United States over the past 2 decades. Among adolescents and adults, pertussis can lead to substantial illness and missed school and work days. Routine vaccination of adults aged 20 to 64 years with combined tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine is cost-effective if pertussis incidence in this age group is greater than 120 per 100,000 population, concludes a new study.

Routine use of Tdap was recommended for all adolescents aged 11-12 years in June 2005. Prior economic evaluations of adult pertussis vaccination strategies have reported disparate results, notes Grace M. Lee, M.D., M.P.H., of Harvard Medical School.

In this study, Dr. Lee and fellow researchers used a model to calculate the health benefits, risks, costs, and cost-effectiveness of three strategies: no adult pertussis vaccination; one-time adult vaccination at 20-64 years; and adult vaccination with boosters every 10 years. The model incorporated factors such as severity of pertussis illness, vaccine adverse events, and herd immunity (spillover effect of immunity on other groups).

At a disease incidence of 360 per 100,000, one-time adult vaccination would prevent 2.8 million cases, and the 10-year booster strategy would prevent 8.3 million cases. As disease incidence varied from 10 to 500 per 100,000, the one-time adult vaccination strategy would prevent 79,000 to 3.8 million adult pertussis cases, while the 10-year booster strategy program would prevent 239,000 to 11.4 million cases.

A one-time adult vaccination strategy would result in 106 million people vaccinated, or about 64 percent of the adult age group, for a total program cost of $2.1 billion, while the 10-year booster strategy would cost $6.7 billion. Both vaccination strategies would cost less than $50,000 per quality-adjusted life year saved, if disease incidence in adults were greater than 120 cases per 100,000 population. This is the amount considered cost-effective for health interventions.

The study was supported in part by the Agency for Healthcare Research and Quality (HS13908).

See "Cost effectiveness of pertussis vaccination in adults," by Dr. Lee, Trudy V. Murphy, M.D., Susan Lett, M.D., M.P.H., and others, in the March 2007 American Journal of Preventive Medicine 32(3), pp. 186-193.

Editor's Note: Another AHRQ-supported article (HS10247) on a related topic concluded that the decreased prevalence of antibiotic resistance with the introduction of heptavalent pneumococccal conjugate vaccine is likely to be partially eroded over time as vaccine-included pathogen serotypes are replaced by resistant clones of nonvaccine serotypes. For more details, see: Hanage, W.P., Huang, S.S., Lipsitch, M., and others (2007, February). "Diversity and antibiotic resistance among nonvaccine serotypes of Streptococcus pneumonia carriage isolates in the post-heptavalent conjugate vaccine era." Journal of Infectious Diseases 195, pp. 347-352.

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