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This chapter is from the book

Vaccines Block Disease

Vaccines represent an alternative way to combat microbes and viruses. Vaccines are preparations of attenuated pathogen or noninfectious parts of pathogens. When eaten or injected, vaccines create a protective immune response against a particular pathogen. Some vaccines are so effective that they eliminate a disease, as was the case with smallpox. The absence of disease means no resistance problem. Unfortunately, we have been unable to make effective vaccines for many pathogens, most notably HIV, tuberculosis, and malaria. Moreover, pathogen diversity can generate resistance to a vaccine (see Box 1-4).

Another serious example concerns the pertussis vaccine. Before vaccination began in the 1940s, pertussis (whooping cough) was a major cause of infant death. In the 1990s, pertussis began a resurgence in countries where most of the population had been vaccinated. Some of the resurgence was due to waning vaccine-induced immunity among the elderly, who increasingly were stricken with whooping cough. However, in Holland between 1989 and 2004, a new strain of Bordetella pertussis, the causative agent, replaced the old one among children, and the number of whooping cough cases increased. The new strain appears to be more virulent and produces more toxin than the old one.30

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