Researchers and public health officials have struggled to explain the resurgence of whooping cough in the United States since the late 1970s, and the suspected shortcomings of the current generation of vaccines are often blamed.
But a new University of Michigan-led study concludes that the resurgence of the highly contagious respiratory disease is the result of factors—including a phenomenon known as the honeymoon period—that began in the middle of the last century, long before the latest vaccines were introduced in the late 1990s.
"Conventional wisdom is that the current vaccine is the problem, but that's not consistent with what we see," said Aaron King, a U-M infectious disease ecologist and applied mathematician.
King and colleagues from the Institut Pasteur, the University of Georgia and Queens University concluded that natural population turnover, incomplete vaccination coverage, and slowly waning protection from a highly effective yet imperfect vaccine best explain the resurgence of whooping cough. The disease can be fatal to infants and is also known as pertussis.
"This resurgence is the predictable consequence of rolling out a vaccine that isn't quite perfect and not hitting everybody in the population with that vaccine," said King, a professor in the U-M Department of Ecology and Evolutionary Biology and in the mathematics department.
The team's findings were published March 28 in Science Translational Medicine. The first author of the paper is Matthieu Domenech de Cellès, formerly a U-M postdoctoral researcher under King, now at the Institut Pasteur in Paris.
"Our results are important because they show that recent trends in pertussis are not necessarily caused by recent changes in epidemiology or biology," said Domenech de Cellès.
"Rather, the contemporary epidemiology of pertussis may be interpreted as a legacy of longstanding immunization practices. It's an important shift of perspective, which makes pertussis a complex but exciting system to study."
The researchers used disease-transmission models and 16 years of age-stratified pertussis incidence data from Massachusetts, along with statistical methods for extracting information from the data. The authors say their results apply to the rest of the United States and to Western Europe.
The other authors of the Science Translational Medicine paper, in addition to Domenech de Cellès and King are Pejman Rohani, a population ecologist at the University of Georgia's Odum School of Ecology and Felicia M.G. Magpantay, formerly a U-M postdoctoral researcher and now at Queen's University in Kingston, Ontario.
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