PLANO, Texas (CBSDFW.COM) – A confirmed case of measles at Plano West Senior High School has Plano ISD leaders and health officials on alert for others.

Meantime, anyone who has been exposed and has not been vaccinated, is being asked to stay away from the school until September 6.

The situation highlights escalating concerns over the growing number of parents who refuse to vaccinate their children.

“I realize that there are religious reasons and other reasons; but, please have all the facts before you choose to make that decision,” says parent Elyse Yoss. “Please know that you are impacting other people’s lives. This is a disease that should have been eradicated years and years ago, and it’s still around because people choose not to be vaccinated.”

Yoss says she is both frustrated and frightened that the choices of others has put her child at risk– when she didn’t have a choice.

“It was the scariest moment of my life,” says Yoss with a grimace, when asked about the moment when she learned that her son, Stephen, then a toddler, was allergic to the measles vaccine.

Stephen Yoss (Robbie Owens – CBS11)

“I had given him a lollipop, so I thought he was choking,” recalls Yoss. “All of a sudden he couldn’t breath, and fell to the ground. I scooped him up and ran him back into the doctor’s office.”

She says it was a rare, severe reaction to a filler in the measles vaccine.

Since then, the family has depended on what medical experts call ‘herd immunity’ to keep him safe. It’s the idea that if enough people are immunized against a disease, it will offer protection to those who cannot tolerate the vaccine. But there’s a problem: More families are simply choosing to not vaccinate.

“I have a friend that was in a class with him,” says Stephen Yoss, a Junior at Plano West. “Apparently he was coughing. He had the rashes all over him.”

Since Stephen is now at risk, he is being warned to stay away and will try to keep up with his classwork from home. He is also encouraging others to consider the consequences of their anti-vaccine choices.

“It’s important to be vaccinated, and you can see that it’s a whole big deal at the school, and it’s really affecting people’s lives,” says Stephen.

“My son is a victim of someone who choose not to be vaccinated– and somebody chose to come to school with the active virus,” adds his mother, Elyse. “My point is if you choose to go through the decision of not vaccinating your children, then you need to be aware of the signs in case they have the disease so they don’t spread it to others.

When asked, Stephen says he would rather be in class and spending time with friends. “No, this is not a break that I wanted. The classes are still going on and I could truly fall behind in some of my classes.”

The Yoss family says school leadership has been wonderful about keeping them informed and assuring them that accommodations will be made to get Stephen the missed coursework.

Still. “It’s very frustrating,” says Elyse. “I don’t think people realize that the decisions they make can have serious impact on the lives of other people, other innocent people. I mean, if this child had stayed home from school, we wouldn’t be in this situation.”