Vaccine critics have downplayed the role of measles in two Texas girls’ deaths, peddled unproven measles treatments and exaggerated the dangers of the vaccine.

Measles cases are most likely being underreported in the United States as public health officials scramble to find resources to address a ballooning outbreak in the Southwest, according to a senior scientist at the Centers for Disease Control and Prevention.

With two measles deaths - both children - in the state, officials struggle to convince communities to vaccinate.