By Jennifer Lindgren CBS 11 News | CBSDFW.COM

TARRANT COUNTY (CBS 11 NEWS) – More children are coming down with whooping cough in Tarrant County, just as warnings are going out to get vaccinated against the bacteria.

Cook Children’s Medical Center took in two more cases in the last 24 hours, hospital officials said. This county has seen double the number of children sick of neighboring counties in North Texas.

The Public Health Department is recommending expectant mothers get the vaccine in the second half of pregnancy.

Locally, preschools and daycares are sending information out to parents and taking precautions to protect infants in their care.

At Primrose School of N.E. Green Oaks, Lynne Groff says her staff is very much tuned into to the health of the children in their care.

“If we have a child that has any kind of cough in the building, we will let the parents know, we think you should probably go get that checked out and make sure it’s not something more than an allergy cough. Once you’ve got that cleared by the doctor, you can come back to school,” she said.

Groff says none of the children at Primrose have been diagnosed with whooping cough, and credits prevention with reason why kids have stayed healthy. The school owners will even pay for staff to get TDaP shots if they so choose.

Over 500 Tarrant County children have had whooping cough this year.  Doctors say, the most serious cases are in infants too young to get the vaccine. That’s why they’re encouraging parents and older children to stay up on immunizations.

Doctors think one of the reasons why we’ve seen so many recent cases may be due to the fading effectiveness of the vaccine.

In 1997, the U.S. switched from administering the DTP vaccine to the DTaP (or TDap).  While the DTaP has less side effects, like fever or rash, the effectiveness wears off after several years.

“It looked like it worked well, but what I gather is it doesn’t stay around as long as it used to,” said Dr. Jerry Simecka, with UNT’s Health Sciences Center.

Dr. Simecka works in vaccine engineering, and says the challenge for those who will engineer a new Pertussis vaccine is to come up with something strong enough for the immune system to respond, but no so strong to trigger side effects.

“So you’re trying to balance these adverse reactions versus positive beneficial effects. You can kind of get caught sometimes. Sounds like what happened here,”  Dr. Simecka said.

(©2013 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)

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