President Trump is now weighing in on the measles outbreak.
He's sending an urgent message to parents and unvaccinated people across America, saying, "They have to get shots. The vaccinations are so important. This is really going around now. They have to get their shots."
This is a reversal for the President, who tweeted in 2014 about an alleged link between vaccines in children and autism.
Right now, the U.S. has the highest number of measles cases on record since the disease was declared eradicated in 2000. There are nearly 700 reported measles cases in 22 states, with 38 reported in California alone.