The University of Arizona will soon begin analyzing blood samples from hundreds of thousands of Arizonans to determine who has been exposed to the virus that causes COVID-19 and developed antibodies against it.

The state of Arizona is providing $3.5 million to test 250,000 health care workers and first responders throughout Arizona.

To lay the foundation for successful statewide implementation, a first phase of testing will begin on April 30 in Pima County and will include 3,000 health care workers and first responders.

With separate funding, approximately 1,500 members of the general public in Pima County, including university students currently residing on campus or in the county, also will be tested to provide a measure of comparison to the health care worker and first responder groups.

Testing for the remainder of the state will expand to health care workers and first responders throughout Arizona on May 7.

The university also will provide antibody blood testing for the remaining majority of its 45,000 students and 15,000 employees with separate funding. Plans for that testing are still being finalized.

What are antibodies?

The COVID-19 antibody tests, which can identify who has developed antibodies to the virus, build upon the work of UArizona Health Sciences researchers Deepta Bhattacharya, associate professor in the College of Medicine – Tucson's Department of Immunobiology, and Dr. Janko Nikolich-Žugich, chair of the Department of Immunobiology.

Antibodies are produced by the immune systems about a week after infection.

"Antibodies are proteins that float in our blood," said Nikolich-Žugich, who also is co-director of the UArizona Center on Aging. "Good antibodies attach to the virus and whisk it away, preventing it from binding to our cells and getting inside."

Current estimates suggest that as many as 50% of people who have been exposed to the virus have experienced few to no symptoms and could have been unwittingly transmitting the virus in the community.

The presence of COVID-19 antibodies means the immune system mounted a response against the virus. Experts do not yet know the amounts of antibodies that are required to fully prevent subsequent infections, but there might be some level of protection. Because we still do not know enough about the virus, protection should not be assumed.

First in the nation: Testing Arizona's health care and first-response workforce

The initial wave of tests will reach health care workers and first responders, whose increased exposure to pathogens puts them at higher risk for infection.

"We're going to be the first to undertake statewide testing of all health care workers and first responders," said Dr. Michael D. Dake, senior vice president for health sciences. "This is critical to understanding what current immunity might be in our community and state, and it's something no one else is doing."

When determining the dates to begin testing, the university aimed to strike a balance between providing health care workers with crucial information quickly and waiting until COVID-19's spread in Arizona has peaked, which models indicate may occur in late April or early May.

"We are trying to give people an understanding of their condition as soon as possible. On April 30, we will start the process in Pima County by testing 4,500 people; then, on May 7, we will expand testing statewide to cover 250,000 health care workers and first responders," Dake said. "With the funding from the state, we now have the opportunity to look at the entire state and inform the rest of the country of the prevalence among these vulnerable workers."

Nikolich-Žugich said the antibody test so far has correctly classified all 30 confirmed COVID-19 patient samples as positive, and has correctly classified all 32 samples obtained before the coronavirus outbreak as negative. Accuracy numbers will be continuously updated as more samples are tested.

The road ahead: Pushing for knowledge

With so few people in Arizona receiving the COVID-19 diagnostic test to date, there is little data on exactly how hard the virus has hit the state. Health care providers and first responders, whose jobs put them directly in COVID-19's line of fire, especially need a better understanding of their exposure to the virus and their immunity to it.

"We expect it's going to be eye-opening," Nikolich-Žugich said. "We certainly expect that exposure to the virus among front-line health care workers and first responders is going to be significantly higher than the general community."

"This is a great opportunity to participate in something that will add to understanding the virus across the whole country, if not the world," Dake added. "People are literally working 24/7 to get this project up and running – pushing, pushing, pushing."