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Science  20 Jul 2001:
Vol. 293, Issue 5529, pp. 397
DOI: 10.1126/science.293.5529.397c

Before mass vaccination in the 1950s, Bordetella pertussis was a major cause of infant death. Despite vaccination, pertussis remains endemic, with a prevalence as high as 1 to 4% and with as many as 30% of people with persistent coughs found to be infected. Mooi et al. investigated the apparent reemergence of pertussis by using DNA fingerprinting to characterize strains collected between 1949 and 1996. Two virulence factors, pertussis toxin and pertactin, exhibited polymorphism, and antibody responses to these proteins correlated with protection from disease. Furthermore, the polymorphism in pertussis toxin is restricted to a subunit that binds to the T cell receptor. It seems that the immune response generated to the vaccine strains may select for novel strains of the pathogen and that the crashes in diversity seen in the 1960s and 1980s may be explained by clonal expansion. Thus, vaccination has shifted the competitive balance among the strains, but it is not yet clear whether polymorphism directly affects vaccine efficacy or reemergence of disease. — CA

Emerg. Infect. Dis.7, Suppl. (June 2001).

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