Dozens of children have contracted measles in the state’s largest outbreak in 33 years. Online, some are blaming vaccines for the disease’s spread.

An outbreak of measles in northwest Texas grew to 159 cases on Tuesday, about a dozen more than health officials reported late last week. The latest update from the Texas Department of State Health Services shows the outbreak remains concentrated in school-aged children who have not received the vaccine that protects against measles,

Measles has sickened nearly 150 mostly unvaccinated people in rural West Texas, and a school-age child has died.