DALLAS (CBSDFW.COM) – While the use of the Johnson & Johnson COVID-19 vaccine is on hold, health officials are urging people to get the Moderna or Pfizer shot.

The technology behind the three shots differs.

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Dallas County had planned on giving out thousands of Johnson & Johnson vaccines at its Fair Park site Tuesday, April 13, but switched to Moderna and Pfizer.

“And that’s what we’ll be doing until the situation resolves,” said Dr. Philip Huang, Director of Dallas County Health and Human Services.

It was welcome news for many of the people who got their shot.

“The Johnson & Johnson vaccine, I was very skeptical,” said Rati Adhikari, who lives in Irving. “So I had made up my mind if there was a change in the vaccine, I would just leave and I’d rather not get vaccinated with Johnson & Johnson.”

Federal officials are looking into a rare blood clotting issue with the Johnson & Johnson vaccine.

It’s similar to what’s been reported in Europe with AstraZeneca’s vaccine, which hasn’t been authorized for use in the U.S. yet.

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“I think this was done appropriately,” said Crystal Howell, an assistant professor of pharmacotherapy at the UNT Health Science Center. “They’re looking at Europe’s data for a similar type of technology. They found six patients here, they said that’s enough, we’re going to investigate.”

Both the Johnson & Johnson and the AstraZeneca are adenovirus vaccines, which means they use a shell of a virus as a vector to carry genetic material into your cells.

“It’s that vector piece, the virus piece, that the Johnson & Johnson vaccine and the AstraZeneca use and the other two vaccines, the Pfizer and the Moderna vaccines, do not use,” Howell said.

Pfizer and Moderna employ newer mRNA technology instead.

Clotting problems haven’t been seen with either of the two vaccines.

“The Moderna, Pfizer are safe and effective,” Dr. Huang said. “And we know what these do is prevent COVID illness. Absolutely don’t use this as a reason not to get vaccinated.”

According to the Texas Department of State Health Services, 13 million Moderna and Pfizer vaccines have been administered in Texas, along with approximately 560,000 doses of the Johnson & Johnson vaccine.

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Of those, not a single dose has resulted in a reported case of blood clotting within Texas.

Caroline Vandergriff