A significant jump in the number of pertussis cases in the U.S. may be due to increasing numbers of nonmedical vaccine exemptions as well as waning immunity among those who have been vaccinated, according to a new study from Harvard researchers.
The incidence of pertussis, or whooping cough—a highly contagious respiratory illness that sends people into coughing fits and which can be deadly, particularly in babies—declined significantly over the course of four decades after a vaccine was introduced in the late 1940s. But the number of cases started creeping back up in the 1980s and 1990s, then increased dramatically in the mid-2000s. In 2012, there were 48,000 reported cases of pertussis in the U.S.—the highest number since 1955.