Re-emergence of Pertussis
Re-emergence of Pertussis
Before the introduction of widespread pertussis immunization in the 1940s, more than 270,000 pertussis cases, associated with 10,000 deaths, were reported annually in the USA. Universal immunization of infants with formalin-treated whole pertussis organisms combined with diphtheria and tetanus toxoids (DTP) beginning in the late 1940s was associated with a marked reduction in disease burden, with the lowest number of cases ever reported in 1976. However, the variability in the quality of the various whole-cell vaccines leading to less effective disease prevention and the high rates of local and systemic adverse events associated with the DTP vaccine led to the search for an improved vaccine. Newer 'acellular' vaccines', consisting of one or multiple purified pertussis antigens rather than the whole organism, were combined with diphtheria and tetanus toxoids (DTaP) and have totally replaced the DTP vaccine in the USA and in many developed countries. However, the number of cases of whooping cough has been increasing, even in countries with high vaccination rates (Figure 1). Although differences in vaccination schedules, composition of the vaccines and disease surveillance systems limit the direct comparison of pertussis burden among countries, a number of locales with comprehensive childhood acellular vaccination programs have clearly reported the increasing incidence of pertussis. For example, during 2010, an estimated 9156 cases of pertussis were reported to the California Department of Public Health for a rate of 23.4 cases per 100,000 persons. This was the highest number of cases since 1947, when 9394 cases were reported.
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Figure 1.
Pertussis cases by year in the USA from 1922 to 2010. The number of cases of whooping cough has been increasing steadily since the 1980s. Reprinted with permission from [2], © Elsevier 2012.
Pertussis Is an Increasing Problem
Before the introduction of widespread pertussis immunization in the 1940s, more than 270,000 pertussis cases, associated with 10,000 deaths, were reported annually in the USA. Universal immunization of infants with formalin-treated whole pertussis organisms combined with diphtheria and tetanus toxoids (DTP) beginning in the late 1940s was associated with a marked reduction in disease burden, with the lowest number of cases ever reported in 1976. However, the variability in the quality of the various whole-cell vaccines leading to less effective disease prevention and the high rates of local and systemic adverse events associated with the DTP vaccine led to the search for an improved vaccine. Newer 'acellular' vaccines', consisting of one or multiple purified pertussis antigens rather than the whole organism, were combined with diphtheria and tetanus toxoids (DTaP) and have totally replaced the DTP vaccine in the USA and in many developed countries. However, the number of cases of whooping cough has been increasing, even in countries with high vaccination rates (Figure 1). Although differences in vaccination schedules, composition of the vaccines and disease surveillance systems limit the direct comparison of pertussis burden among countries, a number of locales with comprehensive childhood acellular vaccination programs have clearly reported the increasing incidence of pertussis. For example, during 2010, an estimated 9156 cases of pertussis were reported to the California Department of Public Health for a rate of 23.4 cases per 100,000 persons. This was the highest number of cases since 1947, when 9394 cases were reported.
(Enlarge Image)
Figure 1.
Pertussis cases by year in the USA from 1922 to 2010. The number of cases of whooping cough has been increasing steadily since the 1980s. Reprinted with permission from [2], © Elsevier 2012.