DALLAS — The first doses of a COVID-19 vaccine began arriving arriving throughout the U.S. on Monday including in Texas, with health care workers first in line to receive the shots.

The Texas Department of State Health Services said 19,500 doses of the vaccine were headed Monday to four sites in Texas: MD Anderson Cancer Center in Houston, Methodist Dallas Medical Center, Wellness 360 at UT Health San Antonio and UT Health Austin’s Dell Medical School.

Methodist Health System began administering vaccinations at about 10:10 a.m. Monday with the first shot going to Teresa Mata, 51, an environmental services employee who cleans the emergency room at Methodist Dallas, spokesman Ryan Owens said. Mata said she was excited to be the fist person to receive it and “wanted to take the risk” because she is diabetic.

“I love my job, but I wanted to protect other persons, I wanted to protect my family and I wanted to protect myself,” Mata said.

Another 75,000 doses of the vaccine were scheduled to be delivered Tuesday to 19 sites in Texas, state officials said, in the largest vaccination campaign in U.S. history.

UT Health Austin-Dell Medical School will vaccinate over 2,900 health care providers, including faculty, residents and medical students, over the next 10 days, according to Amy Young, chief clinical officer at the teaching hospital. Staff vaccinations will be staggered to always maintain a critical workforce in place.

“Part of the reason this is so exciting is that this is our community and the world’s first step to combating this virus going forward,” Young said.

But Young cautioned that “hope on the horizon” is no excuse to ease up on personal responsibility. She implored people to still avoid gatherings, stay six feet away from each other and wear masks when social distancing isn’t possible.

Officials from Texas Medical Center in Houston urged public trust the vaccine. Dr. Paul Klotman, president of the Baylor College of Medicine, said in a press conference that getting vaccinated is helpful to both the individuals and their communities.

“The thing about everyone pitching in, do it for yourself because it will help protect you, but when you get the herd immunity it will help protect people who are unable medically to get the vaccine,” Klotman said.

Texas has seen 24,400 virus-related deaths since the pandemic began, which is second only to New York in overall death count, according to researchers from Johns Hopkins. One in every 332 people in Texas tested positive for the virus in the past week.

On Monday, Texas health officials reported 8,771 newly confirmed cases of COVID-19 and 26 more deaths. The Department of State Health Services also reported 804 probable cases and 9,304 people hospitalized with the virus.