BUILDING IMMUNITY
Preliminary data shows hardly anyone has immunity against COVID-19, but the University of Arizona is hoping to expand both testing and research on the subject.
UA is expanding its free statewide COVID-19 antibody tests for high risk essential workers and will use $7.7 million in federal money to study antibody testing results, officials announced Wednesday at Valleywise Health Medical Center, which is one of the antibody testing sites.
In addition to health care workers and first responders, the free testing is now available to 15 categories of essential workers, including educators, child care workers, grocery and food service workers, solid waste collection workers and journalists.
UA has a website where essential workers may register for the free antibody testing, available in all 15 counties: covid19antibodytesting.arizona.edu.
Duration of COVID-19 immunity remains unclear
It’s still unclear how long immunity against COVID-19 lasts once antibodies are detected, and UA researchers are hoping to find more answers in their yearlong study funded by the U.S. Centers for Disease Control and Prevention.
Researchers also hope to figure out whether there are categories of essential workers who are more vulnerable than others to contracting the virus.
COVID-19 antibody tests measure whether a person has developed antibodies against the SARS-CoV-2 virus that causes COVID-19 illness. In other words, they are not looking for the virus itself but for an immune response against the virus.
“When you get infected by something or vaccinated by something, your immune system starts to develop proteins called antibodies that stick to different parts of the virus,” said Deepta Bhattacharya, an associate professor at the UA College of Medicine-Tucson and a codeveloper of the UA antibody test.
“What we’re measuring are those types of antibodies that could conceivably provide some degree of protection should you get re-exposed again.”
Immunity is measured with a blood test — a finger prick or a blood draw — and is not the same as tests to determine whether someone has an active COVID-19 infection. The tests for active COVID-19 infection are typically conducted with nasal swabs.
Early UA research is showing that immunity persists for two months or more.
“We have a lot of data between, I’d say, Day 40 and Day 60 after symptom onset, and we really don’t see very much (immunity) decay at all. It’s pretty flat,” Bhattacharya said.
“We don’t have nearly as many data points after that. What I’ll say is we have some after about 100 days, and we still see plenty of antibodies.”
COVID immunity remains low in Arizona, results indicate
Statewide, 4.5% of 213,144 blood tests conducted across Arizona since the onset of the pandemic have come back positive for antibodies against COVID-19, data from the Arizona Department of Health Services shows.
In an initial sample of 6,000 tests conducted in Pima County by the UA antibody testing program, 1% of tests came back positive, Bhattacharya said. Preliminary research indicates the rate of false positives for the UA test ranges from 1 in 5,000 to 1 in 10,000, he said.
“Our test is a little bit different than some of the other tests that are out there ... When we began this testing back in May, the caseload in Arizona was fairly low, and so there are some special considerations you have to build into your test to make sure you don’t call someone positive when they are not,” he said.
“If the state only has, say, 1% of people that are positive, even if you have a 99% specific test, that means about 50% of the time you’re wrong. So that was something we really needed to guard against.”
The UA Health Sciences test is an adaptation of the Mt. Sinai Hospital of New York test and was developed in the laboratories of Bhattacharya and Dr. Janko Nikolich-Zugich. The test is conducted with a blood draw from the arm.
“Our test is such that two different independent tests both have to be right in order for us to call you positive,” Bhat
tacharya said.
There are a variety of antibody tests available on the market, some more reliable than others. The UA test is operating under an emergency use authorization by the U.S. Food and Drug Administration for use by authorized laboratories and does not yet have final FDA approval.
UA officials are using $3.5 million in state funding to test about 250,000 essential workers in the newly expanded categories of workers statewide.
UA plans to include 4,000 people in its federally funded AZ HEROES study of COVID-19 immunity among essential workers — half who have tested positive for antibodies and half who have not, said Dr. Jeff Burgess, a professor at the UA’s Mel and Enid Zuckerman College of Public Health and the study’s principal investigator. They hope to have full enrollment within the next two months, he said.
“We are looking at these particular populations because they are all at high risk of exposure to COVID-19. Some of those are pretty clear — for example, if you are a health care worker or an emergency responder, you can be exposed directly to a patient who is COVID-19 positive,” Burgess said.
“For some front line workers, they are going to be interacting with the public very frequently, and some of those members of the public could be positive for COVID-19 as well ... For other essential workers, they may work together, in close quarters, for prolonged periods of time.”
Participants in the study will receive instructions on how to do their own nasal swab testing for active COVID-19, and they will be asked to test themselves weekly, whether they have symptoms or not, by taking a swab and sending their specimens to a lab.
Results will help tell researchers how frequently re-infection occurs, when re-infection occurs, and, if it does occur, how severely it manifests.
“The most important question that we need to answer is how durable is that immune response to COVID-19,” Burgess said. “In other words, if you have it once, how long will it be in months — it could be years — until you are susceptible to another infection.”