The recent outbreaks of whooping cough in the United States may be due, in part, to a change made two decades ago to vaccine ingredients, a new study finds.
In 2012, the United States had about 48,000 cases of whooping cough (also called pertussis) — the most cases since 1955. Although the numbers dropped in 2013 and 2014 to about 29,000 cases yearly, there are still far more cases now than in decades past. Between 1965 and 2002, there were no more than 10,000 cases yearly.
Researchers have proposed a number of ideas for the increase, including increased awareness of the disease and better diagnostic techniques. Others have suggested that fewer people were getting the vaccine, and some thought that the new vaccine’s ingredients were less effective.
In the new study, researchers tested these theories using mathematical models. They used an enormous data set from a variety of sources on whooping cough cases in the U.S. from 1950 to 2009. [Tiny & Nasty: Images of Things That Make Us Sick]