A comprehensive new study of measles and pertussis outbreaks in the United States suggests that adults’ reluctance or refusal to vaccinate themselves and their children have played a key role in the resurgence of diseases that had been completely or largely eradicated in this country.

In an analysis published Tuesday in the Journal of the American Medical Association, epidemiologists scoured published and public health reports of measles and pertussis outbreaks to glean what role vaccination refusal and hesitance played, and how significant the contribution of waning immunity was among the vaccinated.

In measles outbreaks, the researchers found the role of the unvaccinated to be powerful. In 1,416 measles cases occurring in the United States since the disease ceased to circulate in the United States in 2000, 57 percent were in people who had no history being vaccinated. Of the 574 cases of measles seen in unvaccinated individuals, 405 (almost 71 percent) were unvaccinated due to nonmedical exemptions.

Using the reports to draw a “cumulative epidemic curve” — the trajectory of the infection’s spread — the researchers found that unvaccinated individuals tended to be among the first, or within the first few groups of people to contract and pass along measles.