The anti-vaccination movement — where tragically misguided parents are led to believe that vaccines against childhood illnesses are responsible for conditions like autism — is leading to exactly what doctors have always said it would. The states of Oregon and Washington are now dealing with an outbreak of measles, which had previously been eliminated in the entire United States as recently as 2000.

As the Associated Press reports, at least 35 people are now confirmed to have the disease, with around a dozen other suspected cases yet to be confirmed. Of the 35 confirmed cases of the age-old illness, 31 of the infected have never been vaccinated against the disease.

The cheap and incredibly effective measles vaccine found itself at the heart of an incredibly idiotic controversy in the late 1990s when a since-retracted report linked it to autism in children. The factually incorrect report was debunked many times over in the years that followed, but that hasn’t stopped some parents from choosing to not vaccinate their children against diseases like measles, mumps, and rubella.

Failure to vaccinate children lowers what is known as the “herd immunity” of any given population, making it much easier for diseases to spread between individuals who haven’t been vaccinated. After being eradicated in the states, outbreaks of the measles have begun to pop back up, especially in areas where the overall vaccination rate is lower than it’s been in the past.

The state of Washington declared a state of emergency less than a week ago related to the measles outbreak, and health officials are scrambling to contain the contagious disease before it spreads to new areas. The vaccine itself is quite effective, and prevents measles in 97% of people.