Epidemiology of Pertussis and Haemophilus influenzae type b Disease in Canada With Exclusive Use of a Diphtheria-Tetanus-Acellular Pertussis-Inactivated Poliovirus-Haemophilus influenzae type b Pediatric Combination Vaccine and an Adolescent-Adult Tetanus-Diphtheria-Acellular Pertussis Vaccine Implications for Disease Prevention in the United States

Background: During the decade 1998-2007, a combination DTaP5-IPV/Hib vaccine was used exclusively in Canada to immunize infants and young children against diphtheria, tetanus, pertussis, polio, and invasive Haemophilus influenzae type b (Hib) disease. Methods: Medline was used to search for publications during 1996-2008 related to the epidemiology and vaccine prevention of pertussis and invasive Hib disease in Canada. Related abstracts and presentations were reviewed, when available, and epidemiologic data since 1985 were obtained from the Public Health Agency of Canada public Web site. Results: Reports of pertussis have declined substantially in preschool and school-aged children during the past decade, and cyclical peaks in disease incidence have been blunted or eliminated. In provinces and territories where Tdap(5) vaccine has been administered to 14- to 16-year-olds, marked reductions of pertussis have been documented in adolescents as well as younger age groups, possibly due to herd immunity. Incidence rates of invasive Hib disease among Canadian children <5 years declined markedly after introduction of Hib conjugate vaccines, and the disease has remained under control with exclusive use of DTaP5-IPV/Hib vaccine. Most cases of invasive Hib disease occur among unimmunized or only partially vaccinated children. The reduction of Hib case reports has been documented throughout Canada, including among Aboriginal children who are at high risk for this disease. Conclusions: The Canadian experience with DTaP5-IPV/Hib and Tdap(5) vaccines is relevant to file United States because immunization schedules, vaccination coverage rates, and epidemiologic patterns of pertussis and Hib diseases are similar in the 2 countries, and because both vaccines are licensed for use in the United States.