DALLAS (CBSDFW.COM) – As students head back to school, public health officials are concerned not only about a possible COVID-19 outbreak but a measles outbreak, or worse, an outbreak of both at the same time.

This year, with COVID-19, a measles or a whooping cough outbreak at a school could stretch local health resources to the limit.

“It’s not a theoretical concern. It’s real,” said Dr. Jason Terk, a pediatrician with Cook Children’s in Keller.

Despite many students doing school online this year, the Texas Department of State Health Services is still requiring childhood vaccinations for students.

However, this year more parents have put off vaccine shots as many canceled child wellness checkups over the summer to limit exposure to the coronavirus.

According to Dallas County Health and Human Services, the number of doses administered by county’s child vaccine program is down by nearly 50% this year.

Last year, the Dallas County Vaccines for Children (VFC) program reported 49,506 doses of vaccines administered from January to July. This year the number is down to 25,162.

Public health experts say this year’s skipped child wellness checkups is compounded by the trend of North Texas families filing school conscientious vaccine exemptions.

Texas is one of 16 states that allows parents to bypass school vaccine requirements by filing a conscientious exemption.

In the past five years, according to the Texas Department of State Health Services, vaccine exemption rates have nearly doubled in Tarrant County (3.05%) and more than doubled in Dallas County (1.96%). Both counties remain below the state average of 2.24%

Meanwhile, exemption rates in Denton (4.65%) and Collin (4.5%) counties are well above the state average and are pushing 5%, which is often considered the tipping point to maintain “herd immunity”.

In a 2019 CBS 11 I-Team investigation, the I-Team found 16 public and 55 private schools in North Texas that reported more than 5% of their student body filed a vaccine exemption.

As immunization rates drop in North Texas, Terk said the risk for measles, whooping cough and other life-threatening illnesses goes up for everyone.

“When you are not vaccinating, you are extending the risk you are trying to assume to yourself to everybody else around you,“ Terk said.

What school vaccine exemption rate means for COVID-19 vaccine

There is another reason North Texas’ high vaccine exemption rate has public health officials concerned.

Health officials are worried if a growing number of North Texas families are reluctant to get proven childhood vaccinations, what happens when there is a new vaccine for COVID-19?

Jackie Schlegel, the founder of Texans for Vaccine Choice, said since the pandemic began her grassroots political group has gone from 10,000 to more than 14,000 members.

For years, Texans for Vaccine Choice has advocated for the rights of parents to choose whether their children get their school immunization shots.

Recently, Schlegel said her phone has been “ringing off the hook” with people concerned about a potential COVID-19 vaccine.

She said her organization is already preparing for a potential vaccine mandate and for doctors who push a COVID-19 vaccine policy.

“What we can’t afford to do is put so much fear into our families that they can’t even pick up the phone and call their practitioners. We are backing families into a corner.” Schlegel said.

Public health officials says a safe and effective vaccine could end the coronavirus pandemic, but for it to succeed enough people would have to get it.

State governments could mandate people get a COVID-19 vaccine, much like childhood vaccinations are mandated to attend school with exemptions for religious and medical conditions.

However, such a mandate is unlikely to happen in Texas.