In early 2020, Kaitlyn Sadtler envisioned a long, slow season getting her lab up and running. Then covid-19 happened. Within weeks, she and her team were among the first to develop an effective antibody assay capable of determining how many people had been infected with covid-19, whether they’d shown any symptoms or not.
Antibodies tag viruses for destruction and help the body mount an immune response. Those antibodies can linger for months. Existing tests didn’t pinpoint the unique antibodies for the covid-19 virus, leading to false positives among people who had previously been exposed to other coronaviruses. Sadtler and her team at NIH made a highly sensitive antibody test, which uses six different assays to more accurately identify the presence of covid-19 antibodies. Early results published in January confirmed that about 16.8 million Americans had been infected with covid-19 but hadn’t been diagnosed. (Sadtler will update those findings this fall and estimates that as many as one-third of all Americans have been infected with the virus.)
The blood test is sensitive enough to determine whether an individual has antibodies from the virus itself or in response to a vaccine, and it can distinguish between variants of the virus as well. It’s simple and cheap to use, making it practical in both rich and poor countries. “This is a global pandemic,” says Sadtler, “which means we need to think globally.”