Prevention of pertussis among adolescents by vaccination: taking action on what we know and acknowledging what we do not know.

Pertussis is the only disease for which children are routinely vaccinated that is not at historically low levels in the United States. The increases seen in pertussis are not due to ineffective vaccines or programs. The effectiveness of acellular per-tussis vaccine has been demonstrated to be high in both prelicensure studies and postlicensure evaluations, and coverage among vaccine-eligible age groups remains high. However, pertussis continues to strike those who are susceptible because of waning vaccine-induced immunity and infants who are too young to have completed the primary vaccination series. To address the issue of waning immunity, formulations of acellular pertussis vaccine combined with diphtheria and tetanus toxoids for adolescents and adults (TdaP) are now under development in the United States; TdaP vaccines are already licensed and available in Canada, Germany, France, and Australia and are expected in the United States soon. Because a vaccine to prevent pertussis in older children, adolescents , and adults is likely to be available soon, how should policy makers approach its use? Our recommendations for use of TdaP should be guided by our knowledge, and there are things we know well about per-tussis. Outbreaks of pertussis occur in a variety of settings but are most frequently recognized in middle and high schools. Antimicrobial prophylaxis is recommended for close contacts of patients with pertussis, and outbreak response is a complex , costly, and disruptive activity for schools and local health authorities. The rates of hospitalization, serious complications , and death among adolescents are low, but cough illness due to pertussis is prolonged, and the health impact—in terms of medical visits, antimicrobial treatment, and experience of illness—is significant. Currently, these school-based outbreaks are not preventable, and the only strategies for control are identification , isolation, and prophylaxis of contacts. But there is much that is not known about pertussis. It is unclear whether the recent increases in reported disease are real or are artifacts of increased recognition; the increase in reported cases among young infants, coupled with relatively stable rates of reported disease among older infants and preschool-aged children, suggests that there may be a real increase in the circulation of Bordetella pertussis in some age groups [1]. But there is no doubt that ascertainment of pertussis is variable and incomplete in most age groups. Physicians may not consider the diagnosis, especially in adolescents and adults, because of a lack of clinical awareness that pertussis occurs in …