How do we get back to some sort of normalcy in this country?

A new normal and our antibody tests part of that solution.

Can the tests show if you've been exposed to the virus without even knowing?

Do you have some sort of immunity tonight?

The World Health Organization and what they said about immunity from the virus, saying they do not know yet whether having this once means you won't have it again.

Here is ABC is mapped up in tonight the World Health Organization tonight, acknowledging it simply does not know if those who've had Corona virus would have immunity or if there's a chance you could get it more than once, a top official says, We simply do not know.

So right now the information is mixed.

We need much more information from recovered patients and in South Korea, a small study showing people testing positive twice.

Authorities say they don't know if it's a reactivation of the virus in their body or a new infection.

But here in the U.

S.

Authorities remain hopeful that was you've had it, or at least been exposed to it, you might have some immunity.

Here in California, there are now multiple trials underway to test for those antibodies.

Tell tell proteins in the blood that show exposure to the virus way were there as 50 firefighters, among the first to be tested.

But the CDC remains concerned about the accuracy and reliability of antibody test, and one clinician administering these new tests says it's possible immunity could weaken over time.

A lot of people say that the antibody test is the panacea for this virus, but you're saying it's not quite from what we've seen.

We don't know if the antibodies disappear after a certain period of time.

We believe that means theoretically, you lose that immunity.

You could be susceptible to a second infection.

Meantime, tonight, the race is on to help the most severe patients still fighting for survival, we have reported here The FDA has fast tracked an experimental treatment that allows patients who've had the virus and recovered to donate their blood.

It's called convalescent plasma.

Jason Garcia is a patient in San Diego who recovered from the virus.

You're giving a donation to help other hopeful on age old technique once used after the Spanish flu of 1918.

Work again.

It's such a small thing to have such a huge impact.

He's donated to three patients, one of whom doctors say has shown remarkable improvement.

And in Florida tonight, 52 year old Kevin Raph L.

Was on a ventilator, in a coma and near death, and just four days ago he started receiving donor plasma.

And last night his wife, Stacy, got a surprise from their doctor.

A facetime call with her husband.

And we just started talking to him.

I told him I said, Kevin, you've been asleep for a week.

It's time to wake up.

It's Easter morning and God has performed a miracle.

You need to come home to us and we love you were waiting for you.

It is so good to see Kevin emerging from that coma.

But at this point, his doctors air yet unwilling to draw a correlation between that plasma treatment and his apparent recovery.

They say while the treatment has worked against other viruses in the past, with Cove it this plasma treatment is still uncharted territory.

David.

Yeah, we still don't know, but it certainly is hopeful on Mac up on our thanks to Matt will have much more of his reporting a little later tonight on Nightline.

Hi, everyone.

George Stephanopoulos here.

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