The National Institutes of Health have started recruiting for a new study that aims to determine how many adults in the US who have not had a confirmed infection with SARS-CoV-2 carry antibodies to the virus, indicating that they were previously infected.

The study, called "SARS-CoV-2 Pandemic Serosurvey and Blood Sampling," is conducted by the National Institute of Allergy and Infectious Diseases and the National Institute of Biomedical Imaging and Bioengineering, with additional support from the National Center for Advancing Translational Sciences and the National Cancer Institute. The researchers plan to collect and analyze blood samples from up to 10,000 volunteers.

"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 NIAID Director Anthony Fauci in a statement. "These crucial data will help us measure the impact of our public health efforts now and guide our COIVD-19 response moving forward."

The investigators plan to analyze blood samples for two types of antibodies, anti-SARS-CoV-2 S protein IgG and IgM, using an enzyme-linked immunosorbent assay (ELISA) developed at NIAID and NIBIB. Participants with positive test results may undergo additional tests to evaluate their immune response to the virus. The results may explain why these cases were less severe than those that resulted in hospitalization.

Healthy adults over the age of 18 from across the US who have no confirmed history of COVID-19 and have no current symptoms are eligible to participate and will be enrolled over the phone.

Study participants working at the NIH Bethesda campus will have their blood drawn at the NIH Clinical Center, while other volunteers will take their own blood samples at home, using at-home blood collection kits provided by Neoteryx, a medical device firm based in Torrance, California.

"Researchers have considerable experience using these at-home blood collection kits to track the spread of other infectious diseases like influenza, and this method is safe, effective and easy-to-use," said Kaitlyn Sadtler, study lead for laboratory testing and chief of NIBIB's section for immunoengineering, in a statement.