MANHASSET, N.Y. (CBSNewYork) — Many Americans with an autoimmune disease have had a poor response to COVID-19 vaccines, placing them at extremely high risk.

An important National Institutes of Health trial began Wednesday to determine if a third vaccine will produce antibodies, CBS2’s Jennifer McLogan reported.

In all, 600 immunocompromised people from around the country age 18 and above are now volunteering for a third vaccine — not a booster.

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The NIH clinical trial will determine why Robert Cass of Elwood and others produced almost no antibodies.

“The first two shots didn’t take as well as we’d hoped and now this study is really to see if a third dose is going to make a big difference,” Cass said.

COVID VACCINE

Cass is one of an estimated 10 million people in the U.S. with a compromised immune system. He takes transfusions for lung disease. Researchers are eager to know if it’s the medication or the disease that is suppressing the benefits of vaccine.

Dr. Meggan Mackay is principal investigator at Feinstein Institutes for Medical Research.

“This trial is for patients with autoimmune disease who were vaccinated but failed to produce an antibody response,” Mackay said.

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Like others with autoimmune disease, after two shots and few antibodies, Cass is at risk.

“My wife is obviously very concerned that I am immune compromised. I have grandchildren that I don’t get to see as often because this is a very precarious time,” Cass said.

A dad, grandfather, and software engineer, Cass knows his body would not do well with COVID-19.

“I’m glad to be a part of this. This is wonderful, that it is the first time that we are studying this. I can’t wait to see what comes of it,” said Feinstein clinical researcher Pascale Hogu.

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The trials are being conducted on Long Island and in Philadelphia, Ann Arbor, and Oklahoma City.

“It feels great. I’m happy that I’m able to be a part of it,” Cass said. “I’m glad that this is going to benefit other people. I just have a really good feeling.”

Cass’ antibody response will show in about four weeks. The NIH plans to release preliminary study results from all 600 participants in November.

Jennifer McLogan