The most likely cause of the steady increase of measles outbreaks in the U.S. is people who do not vaccinate against the virus, according to a report published Oct. 3 in JAMA.
A team of researchers from the CDC — led by Nakia Clemmons; Gregory Wallace, MD; and Manisha Patal, MD — analyzed 1,789 measles cases reported to the CDC from January 2001 through December 2015. They found that 70 percent of the individuals with the disease were unvaccinated.
The researchers found that the rate of measles increased over time with the majority of outbreaks, with at least 20 cases reported, occurring after 2010. In addition, imported cases of measles have declined over time, while the number of people infected on American soil has risen.
While measles vaccination rates still remain high across the country, various communities are falling below the 90 percent to 95 percent herd immunity level that is needed to prevent an outbreak, according to the study.
The trend of decreasing vaccination rates and increasing measles cases is significant because it may suggest "increased susceptibility and transmission" in U.S. communities, with fewer vaccinated residents, Ms. Clemmons told The Washington Post.
The findings add to the body of evidence that the return of measles, after it was eliminated nationally in 2000, is largely because of people who reject vaccinating their children, according to the report.
To read the full report click here.