Patients who have recovered from the virus now willing to donate blood plasma that could help others.

But some say they're running into roadblocks.

Here's NBC's Kaylee Hartung.

Tonight, 78 year old Jim Cassis is in a Sacramento.

I see you on a ventilator fighting for his life.

Um, as many shares as possible would help.

We're desperate.

His daughter, Amber, made this emotional plea on social media for her father, an avid golfer with a black belt in taekwondo.

We're trying to get these antibodies to give to my father so he can fight off this virus.

If you think that you're qualified candidates of help, we would be so appreciative on DSO with my dad.

The FDA has authorized trials at a handful of institutions throughout the country using plasma from people who've recovered from Cove in 19 rich with antibodies to the virus to see if it could help those infected.

One of the first trials is underway in Syracuse, New York Allesandro Miller was the first person to donate their, and I am very grateful that I'm in the position that I can help.

Testing for the virus antibodies is critical to finding people who can donate.

But thousands of people are still being refused tests to know if they have cove it to begin with.

Here in California, there's that large backlog to process.

It is a complicated process, so you need a lot of resource is and at a time where our health system is pushed to the brink.

After hundreds of people reached out wanting to help, Jim's family learned the potential plasma treatment isn't yet available to him.

And it's incredibly frustrating because people like my dad are going to suffer from this if people don't start taking option and start moving faster, all right, Kaylee Hartung joins us now from her home and Kaylie, you had the virus.

You're now recovered and you're trying to donate your plasma, but you're having trouble as well.

That's right, Tom.

I've been trying, but it's not a simple it's just raising your hand.

I've been told I need another cove in 19 tests to prove that I'm no longer carrying the virus or be asymptomatic for 28 days.

So there are very few people in this country who have been asymptomatic long enough to volunteer.

And even then, most hospitals and blood banks are not yet set up to take in these kinds of donations.

Tom Kaylee Hartung breaking it down for us.

All right, Kayleigh.

Thank you for that.

Hi, everyone.

George Stephanopoulos here.

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