Study: Less Than 86% Of Disney Guests Were Vaccinated Against Measles

It's been nearly three months since a measles outbreak broke out in Disneyland. Since then, the highly-contagious disease has spread, infecting 145 people in the U.S. and a dozen others in Canada and Mexico. Although it's not clear who was the first person to bring measles to the Anaheim theme park, it turns out that it spread so widely because less than 86% of Disneyland guests were vaccinated, a new study says.

The researchers behind a JAMA Pediatrics study that was released on Monday crunched some numbers, and found that the percentage of people in Disneyland who were vaccinated at the time was no higher than 86%, and could have been as low as 50%, according to the L.A. Times. In order to have herd immunity, meaning a large enough percentage of the population to be immune to a disease, the percentage of people vaccinated would have to be between 96% and 99%.

They calculated this using historical data that looked into how quickly measles can spread to unvaccinated people, as well as to how many people.

While health officials declared that measles were pretty much wiped out from the U.S. in 2000 due to vaccinations, the number of measles cases have increased over the last year, mostly thanks to folks who aren't vaccinated. Those anti-vaxxers—including some who think that organic nutrition is good enough to stave off measles—have been facing some blowback. California state health officials have told the unvaccinated to stay away from Disneyland, and officials at Orange County and Riverside schools have asked for unvaccinated students to stay at home during measles scares. Even though the state requires that students get vaccinated for measles, parents who are opposed to vaccines for whatever reason can sign a personal belief waiver to sidestep that requirement. However, that could very well change as California legislators proposed a bill last month that aims to repeal the personal belief exemption.

Measles is a respiratory disease that spreads through the air through coughing and sneezing. A person who's contracted measles can be contagious up to four days before and after the rash begins to show. The symptoms for this disease include fever, cough, runny nose, red eyes, and a rash covering the entire body, and will appear about a week to two weeks after being infected. There's no treatment for measles, but most people usually recover after a few weeks.