As he toured the state earlier this month to promote his plans to reopen Florida, Gov. Ron DeSantis repeatedly touted testing for COVID-19 antibodies as a signal that immunity may be lurking, undetected, among the population.
“If you're a healthcare worker and you have the antibodies, then obviously you have immunity,” he said at a May 5 press conference in Sarasota.
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“The good thing about it is once the antibodies develop, if you test positive for the antibodies, it's not like you're going to lose the antibodies the next day,” he said the next day at Hard Rock Stadium in Miami Gardens. “So this is very important, particularly for our first responders and our health care workers to know who has the antibodies.”
But doctors and researchers say they do not yet know if being infected, and producing antibodies, provides immunity. Both the Centers for Disease Control and Prevention and World Health Organization say it's not yet clear if an infection provides immunity.
“We don't know at this point if those antibodies mean you are immune to getting the infection again,” said Dr. Patrice Harris, president of the American Medical Association. “I can’t emphasize that enough.”
If the virus behaves like other viruses, Harris said the presence of antibodies could provide immunity. But for now that remains unclear, she said. And there have been early studies suggesting antibodies persist for nearly a month, suggesting immunity may be prolonged.
But the association is not recommending people get antibody testing, unless they are participating in studies overseen by health professionals. And confirming whether an infection provides prolonged, durable immunity will likely take months, she said.
“We have some data from China because they were hit early on. And so the scientific community across the world, across the globe, are looking at this data. But, of course, you know, the longitudinal study is necessary because we won't be able to say if you have immunity for a year until a year has passed.”
The governor's office did not respond to repeated requests for clarification between May 5 and May 12. The Florida Department of Health initially said it would consider an interview with Dr. Scott Rivkees, Florida’s surgeon general, but did not respond to follow up emails.
So how did antibody testing land in the center of the debate about how Florida and the rest of the country reopens? Antibody testing became a stopgap amid a national shortfall of diagnostic testing early in the pandemic, said Erin Kobetz, the cancer researcher overseeing the University of Miami’s antibody study for Miami-Dade County.
“We'd been trying to wrap our heads around what's happening and who's infected and to come up with ways to bridge gaps in the availability of widespread testing,” she said.
Antibody testing could possibly determine if people were infected, “but it doesn't necessarily tell us when they were infected or if that infection confers long-term immunity,” she said.
After an infection, like with any virus, people start making antibodies to fight it. The first to appear are called Immunoglobulin M. Another antibody, Immunoglobulin G, takes longer to form and represents the later stages of an infection.
“If they had those antibodies, plus seven days of no symptoms, they theoretically could return to the front line safely or more safely than somebody who's yet not producing those antibodies,” Kobetz said.
That’s because they would no longer be in danger of infecting other people, she said, not because they’re immune.
To figure out immunity, researchers need to trace the arc of the disease.
“You follow people in the community who are unexposed, to the point that they are exposed,” she said. “And then you continue to follow them over their illness course and to the dissolution of antibodies.”
Kobetz says the UM study doesn’t have the resources to conduct a longitudinal study.
Antibody testing also works only if antibodies are still present.
“The window in which you were sick and when you received antibody testing could potentially be too long to pick up a prior infection because the antibodies we know don't stick around indefinitely,” she said.
Antibody testing has also come under scrutiny after unreliable tests hit the market after the Food and Drug Administration relaxed its screening rules in March to allow more tests to become available. This month, the agency said “unscrupulous actors marketing fraudulent test kits," and taking advantage of the "Americans' anxiety" had caused it to again tighten rules.
It gave test makers 10 days to submit data confirming accuracy. So far, the agency has only sanctioned a dozen tests, Harris said.
That led UM to suspend its study last week until it can obtain an authorized tests. Results from testing started in April will still be used in the study, media relations director Diana Gonzalez said in an email Monday.
The changing rules and uncertainty likely helped cloud the issue. At a hearing before a U.S. senate committee last week, Sen. Rand Paul echoed DeSantis, and pushed Dr. Anthony Fauci to acknowledge that antibodies confer immunity.
“As I've often said, I again repeat, you can make a reasonable assumption that it would be protective,” Fauci testified. “But natural history studies over a period of months to years will then tell you definitively if that's the case.”
Before doctors make recommendations based on antibodies, they want to be sure, Fauci said in an April interview with the Associated Press.
“The worst possibility is if we're actually wrong about that and we say, OK, you're protected. People go back to work thinking that they're protected, do not really adhere as closely to the kinds of things that would prevent you from getting infected. And they wound up getting infected.”
For now, everyone should assume they’re infected, and no one has immunity, Harris said.
“We should be wearing those face coverings and we should see wearing face coverings not as infringement on someone's right, but as a bold action we can take to protect others around us,” she said.
Guidelines could change, she said, depending on how widespread COVID-19 in particular areas and the amount of testing.
“It's important that whatever jurisdiction is making decisions,” she said, “that they make decisions based on the science and the evidence and data and not politics.”
How much diagnostic testing is needed to prevent a second wave of infections as the state reopens may also be unclear.
The University of Florida’s Emerging Pathogens Institute worked with an international team of scientists to build a model this month predicting the number. The model found that if half of infected people with symptoms could be identifed — and 40 percent of their contacts traced — then just nine percent of those contacts would need to be quarantined.
That number, the researchers said, would keep hospitals from being overwhelmed. But the actual number of tests needed depends on the number of people infected, researcher Tom Hladish said on the Florida Roundup.
“The amount of testing you need to do scales with the number of people who are infected,” he said. “If this blows up and we get a large second wave, then it's going to rapidly become inadequate.”