Scientists are collecting blood samples from 10,000 healthy people to figure out how much the coronavirus has really spread in the US

• The National Institutes of Health is enrolling 10,000 healthy people in a study that seeks to determine how far the novel coronavirus has spread.
• They'll use blood samples to detect antibodies the body produces to fight off infection.
• Whereas typical coronavirus tests measure for active infection, the antibody tests can tell whether people have been exposed to the virus in the past.
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The National Institutes of Health is enrolling up to 10,000 healthy people in a study that seeks to determine how many people have immunity to the novel coronavirus.

Investigators will take blood from participants and test it for antibodies the body produces to fight off infection. The idea is to figure out the true number of people who've been exposed to the virus, whether or not they had symptoms.

The study is one of many public and private efforts to expand "serology" or immunity tests in the US. Since the tests can measure a response to the virus long after it's occurred, they've been called the next frontier of coronavirus screening and should help the NIH understand the extent of its spread.

Read more: Tests that can tell if you're immune to the coronavirus are on the way. Here are the companies racing to bring them to the US healthcare system.

Led by researchers at the National Institute of Allergy and Infectious Diseases and the National Institute of Biomedical Imaging and Bioengineering, the rollout is one of the biggest serology efforts at the federal level thus far.

"This study will give us a clearer picture of the true magnitude of the COVID-19 pandemic in the United States by telling us how many people in different communities have been infected without knowing it, because they had a very mild, undocumented illness or did not access testing while they were sick," said Anthony S. Fauci, a key member of President Donald Trump's coronavirus task force and the director of NIAID, in a press release.

Whereas reporting of confirmed cases in the US has mostly relied on molecular tests that determine the active presence of the virus in a person's airways, NIH investigators will analyze the blood for two kinds of antibodies indicating prior exposure, proteins called IgM and IgG.

The former develops quickly and typically lasts for a week or two. The latter has a longer life and is involved in the body's secondary immune response, according to the NIH.

"An antibody test is looking back into the immune system's history with a rearview mirror," said Matthew J. Memoli, the study's principal investigator.

Volunteers near Washington, DC will give blood in-person at the NIH campus in Maryland. The NIH will ship kits made by medical device company Neoteryx to other participants for at-home use.

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The study is not open to people with current coronavirus symptoms or those with laboratory-confirmed histories of the virus. People who suspect they recovered without tests or never had symptoms consistent with the virus in the first place are encouraged to enroll, however.

People interested in joining can contact the NIH at clinicalstudiesunit@nih.gov and will be asked to consent over the phone. Enrollees can request their results after a prolonged waiting period of weeks or months, according to the NIH.

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