A child who was hospitalized with measles has died from the illness in West Texas, state and local health officials announced Wednesday. It is the first death in a measles outbreak that has infected more than 120 people since late last month. 

Lubbock health officials and the Department of State Health Services said the patient who died was an unvaccinated school-aged child who passed away in the last 24 hours.

As of Wednesday, the Texas health department reported at least 18 hospitalizations in the outbreak, which is primarily affecting children and teenagers. Nearly all of those who have been reported ill in Texas were unvaccinated. Nine cases have been reported in neighboring New Mexico.

As many as 1 in 20 children with measles will develop pneumonia, CDC data shows. In some cases, measles can cause severe infections in the lungs and brain that can lead to cognitive issues, deafness or death.

While most people’s symptoms improve, about 1 in 5 unvaccinated people will be hospitalized, 1 out of every 1,000 will develop brain swelling that can lead to brain damage, and up to 3 of every 1,000 will die. 

Measles is one of the most contagious infectious diseases, but doctors and health officials say the vaccine, which is normally given as part of the combination measles-mumps-rubella (MMR) vaccine, is highly safe and effective.

Dr. Céline Gounder, CBS News medical contributor and editor-at-large for public health at KFF Health News, said recently on “CBS Mornings” that lower vaccination rates allow measles to spread, noting that even a slight dip in coverage can lead to outbreaks.

“This is a measles outbreak that began in a very close-knit, rural, Mennonite community that has very low vaccination rates. And unfortunately, we have seen vaccination rates exemptions … really soar in Texas in recent years,” she said. 

According to recent KFF polling, about 17% of parents say they have skipped or delayed a vaccine dose for their children. 

“This is up from about 10% just two years ago. So we’re really seeing a lot of exemptions [and] concerns about vaccination that are not warranted,” Gounder said. 

Before a vaccine became available in the 1960s, between 400 and 500 Americans — mostly children — died every year from measles.