Acellular pertussis vaccine for adolescents.

BACKGROUND The use of whole-cell pertussis vaccine has led to a significant decline in incidence of the disease among children. This change in the epidemiological profile led to an increased number of cases among teenagers and adults, as a result of loss of immunity to the disease or vaccine after approximately 10 years. An increased number of cases was also observed among non-immunized or partially immunized infants. Licensure of the DTP vaccine against diphtheria, tetanus, and acellular pertussis formulated specifically for patients over 10 years of age (Tdap) suggests the possibility of controlling pertussis in the most affected age groups over the past few years. SOURCES OF DATA Data were collected from MEDLINE. The research was limited to the period between January 1995 and January 2006. SUMMARY OF THE FINDINGS In some countries there are two Tdap vaccines licensed for patients over 10 years of age. One of them contains five immunogenic components of Bordetella pertussis (pertussis toxin, filamentous hemagglutinin, fimbriae 2 and 3, and pertactin), and the other contains three components (pertactin, filamentous hemagglutinin, and inactivated pertussis toxin), the latter being the only one licensed in Brazil up to now. Although the composition of the two vaccines differs, studies show that they have similar effectiveness and immunogenicity. Some authors, however, emphasize that it is difficult to make a precise assessment of the immunological response to the vaccine and its duration. Several countries currently recommend the use of Tdap vaccine for adolescents. Canada has extended the target population up to 54 years of age. The guideline is that this group should receive one dose of the vaccine to reinforce the basic immunization scheme. This is based on study results that show that the vaccine-induced immunity lasts for around 6 to 12 years. Assessments of the economic impact of routine use of the vaccine in adolescents showed a positive cost-benefit ratio. Results of the epidemiological impact depend on the quality of diagnosis so that data reflect the reality of the disease. CONCLUSIONS Although some questions remain to be clarified, the literature indicates the possibility of solving the "reappearance" of whooping cough (pertussis) with the use of Tdap vaccine. Perhaps the strategy of using a second booster dose in adolescence to replace the double diphtheria and tetanus vaccine should be adopted immediately.