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Dr. Aaron Kheriaty, a psychiatry professor at the University of California, Irvine, felt he didn’t need to be vaccinated against Covid-19 because he’d fallen ill with the disease in July 2020.
So, in August, he sued to stop the university system’s vaccination mandate, saying “natural” immunity had given him and millions of other people better protection than any vaccine could.
A judge last week dismissed Kheriaty’s request for an injunction against the university over its mandate, which took effect Sept. 3. While Kheriaty intends to pursue the case further, legal experts doubt that his and similar lawsuits filed around the country will ultimately succeed.
That having been said, evidence is growing that contracting SARS-CoV-2, the virus that causes Covid-19, is generally as effective as vaccination at stimulating your immune system to prevent the disease. Yet federal officials have been reluctant to recognize any equivalency, citing the wide variation in Covid patients’ immune responses to infection.
Like many disputes during the Covid pandemic, the uncertain value of a prior infection has prompted legal challenges, marketing offers and political grandstanding, even as scientists quietly work in the background to sort out the facts.
For decades, doctors have used blood tests to determine whether people are protected against infectious diseases. Pregnant women are tested for antibodies to rubella to help ensure that their fetuses won’t be infected with the rubella virus, which causes devastating birth defects. Hospital workers are screened for measles and chickenpox antibodies to prevent the spread of those diseases. But immunity to Covid seems trickier to discern than immunity for those diseases.
The Food and Drug Administration has authorized the use of Covid antibody tests, which can cost about $70, to detect past infections. Some tests can distinguish whether the antibodies came from infections or vaccines. But neither the FDA nor the Centers for Disease Control and Prevention recommend using the tests to assess whether you’re, in fact, immune to Covid. For that, the tests are essentially useless, because there’s no agreement on the amount or the types of antibodies that would signal protection from the disease.
“We don’t yet have full understanding of what the presence of antibodies tells us about immunity,” said Kelly Wroblewski, the director of infectious diseases at the Association of Public Health Laboratories.
By the same token, experts disagree about how much protection an infection delivers.
How does natural immunity compare to vaccination?
In the absence of certainty and as vaccination mandates are imposed across the country, lawsuits seek to press the issue. People who claim that vaccination mandates violate their civil liberties argue that infection-acquired immunity protects them. In Los Angeles, six police officers have sued the city, claiming they have natural immunity. In August, law professor Todd Zywicki alleged that George Mason University’s vaccination mandate violated his constitutional rights, given that he has natural immunity. He cited a number of antibody tests and an immunologist’s medical opinion that it was “medically unnecessary” for him to be vaccinated. Zywicki dropped the lawsuit after the university granted him a medical exemption, which it claims was unrelated to the suit.
Republican lawmakers have joined the crusade. The GOP Doctors Caucus, made up of Republican physicians in Congress, has urged people leery of vaccination to instead seek antibody tests, contradicting CDC and FDA recommendations. In Kentucky, the state Senate passed a resolution granting equal immunity status to those who show proof of vaccination or positive antibody tests.
Hospitals were among the first institutions to mandate vaccinations for their front-line workers because of the danger that they could spread the disease to vulnerable patients. Few have offered exemptions to those previously infected. But there are exceptions.
Two Pennsylvania hospital systems allow clinical staff members to defer vaccination for a year after having tested positive for Covid. Another, in Michigan, allows employees to opt out of vaccination if they present evidence of infections and positive antibody tests in the previous three months. In those cases, the systems indicated that they were eager to avoid staffing shortages that could result from the departure of vaccine-shunning nurses.
For Kheriaty, the question is simple. “The research on natural immunity is quite definitive now,” he told KHN. “It’s better than immunity conferred by vaccines.” But such categorical statements are clearly not shared by most in the scientific community.
Dr. Arthur Reingold, an epidemiologist at the University of California, Berkeley, and Shane Crotty, a virologist at the respected La Jolla Institute for Immunology in San Diego, gave expert witness testimony in Kheriaty’s lawsuit, saying the extent of immunity from reinfection, especially against newer variants of Covid, is unknown. They noted that vaccination gives a huge immunity boost to people who have been ill previously.
Yet not all of those pushing to recognize past infection are vaccination critics or torchbearers of the anti-vaccine movement.
Dr. Jeffrey Klausner, a clinical professor of population and public health sciences at the University of Southern California, co-authored an analysis published last week that showed that infection generally protects for 10 months or more. “From the public health perspective, denying jobs and access and travel to people who have recovered from infection doesn’t make sense,” he said.
In his testimony against Kheriaty’s case for “natural” immunity, Crotty cited studies of the massive Covid outbreak that swept through Manaus, Brazil, early this year, which involved the gamma variant of the virus. One of the studies estimated, based on tests of blood donations, that three-quarters of the city’s population had already been infected before gamma arrived. That suggested that previous infection might not protect against new variants. But Klausner and others suspect that the rate of previous infections presented in the study was a gross overestimate.
A large study in August from Israel, which showed better protection from infection than from vaccination, may help turn the tide toward acceptance of prior infection, Klausner said. “Everyone is just waiting for Fauci to say, ‘Prior infection provides protection,’” he said.
When Dr. Anthony Fauci, the top federal expert on infectious diseases, was asked in a CNN interview last month whether infected people were as well protected as those who have been vaccinated, he hedged. “There could be an argument” that they are, he said. Fauci didn’t immediately respond to a KHN request for further comment.
CDC spokesperson Kristen Nordlund said in an email that “current evidence” shows wide variation in antibody responses after Covid infection. “We hope to have some additional information on the protectiveness of vaccine immunity compared to natural immunity in the coming weeks,” she said.
A “monumental effort” is underway to determine what level of antibodies is protective, said Dr. Robert Seder, the chief of the cellular immunology section at the National Institute of Allergy and Infectious Diseases. Recent studies have taken a stab at a number.
Dr. George Siber, a vaccine industry consultant and co-author of one of the papers, said antibody tests will never provide a yes-or-no answer about Covid protection. “But there are people who are not going to be immunized,” he said. “Trying to predict who is at low risk is a worthy undertaking.”