The measles vaccine uses a weakened virus that's never been shown to spread to others. Samples from the outbreak in Texas also show that a wild-type virus is responsible. Yet, social media posts have falsely claimed that the outbreak is due to a vaccine strain.

A measles outbreak in Kansas has more than doubled to nearly two dozen cases over the last week, according to state health officials, who said they identified a “possible link” between confirmed cases of the highly contagious illness and a larger outbreak in Texas and New Mexico.