The incidence of pertussis, or whooping cough
, has increased in the United States since the 1980s, despite high rates of children receiving vaccines to protect against the disease.
Researchers with the U.S. Centers for Disease Control and Prevention and public health offices in Oregon and Minnesota tracked the immunization records
of children in the two states and compared them to pertussis surveillance data. They identified an increase in the incidence of pertussis in children in the six years after receiving the fifth dose of DTaP, suggesting immunity had waned. The incidence of pertussis in children aged 7 to 10 in Minnesota increased more than sixfold from 2007 to 2010. From 2006 to 2010, cases among 7- to 10-year-olds in Oregon also rose, but to a much lesser degree. Recent studies, including this one, suggest that protection from the DTaP series begins to wane after vaccination, which helps to explain the growing incidence of pertussis in 7- to 10-year-olds who previously had a low risk of disease, presumably due to vaccination with whole-cell vaccines rather than the acellular pertussis vaccine now in use.
Study authors conclude that because new vaccines are distant on the horizon, it’s important to maintain high immunization rates with existing vaccines to protect vulnerable populations as more disease is circulating in the community.