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WASHINGTON — Among scientists, there’s little debate: People who get sick with Covid-19 develop at least some protection against being infected in the future.

But exactly how much protection they have, and how long it lasts, are the subjects of the country’s latest Covid-19 controversy. For the past month, university employees, professional athletes, and conservative lawmakers across the country have argued they should be exempted from increasingly strict vaccine mandates because, scientifically speaking, they don’t need them: They’re already protected by their body’s own immune response.


This debate, however, is decidedly different from other political fights that have undermined the U.S. coronavirus response. Unlike the conspiracy-riddled arguments about hydroxychloroquine or ivermectin, the concept of natural immunity has a rational basis and data to support it. Like the other debates, though, it has devolved into partisan bickering, highlighting how the state of American politics has ruined the country’s scientific process and made nuanced debates all but impossible.

“It’s hard to know where the data will finally land, and it’s hard to know where the shouting will land,” said Wendy Parmet, a Northeastern University law professor who has written extensively about the legality of government-imposed quarantines and vaccine mandates. “People on the right scream, so people on the left say no. We’re in this horrible, awful feedback loop of vitriol right now.”

There’s still no scientific consensus about the exact strength or durability of the natural immunity a person gains when they recover from Covid-19, or how much it varies from person to another.


In August, the Centers for Disease Control and Prevention released a study showing that vaccination after a Covid infection provided more powerful protection than immunity derived only from a previous coronavirus infection. Unvaccinated people who’ve previously had Covid-19 are twice as likely to be re-infected with the virus compared to those who are fully vaccinated after being sick, according to the data. It prompted Rochelle Walensky, the agency’s director, to plead with Americans: “If you have had Covid-19 before, please still get vaccinated.”

Increasingly, though, researchers are acknowledging that the protection from natural immunity can be potent.

Later in August, a study in Israel showed that people who have recovered from Covid-19 get symptomatic breakthrough infections 27 times less often than people who’ve been vaccinated, though experts cautioned that it is not conclusive, and could fail to account for external factors like underlying health conditions.

It’s a basic principle of immunology that becoming sick with an infectious disease gives the body protection against the same disease in the future, said Marcus Plescia, the chief medical officer of the Association of State and Territorial Health Officials. People who have recovered from Covid-19 and therefore view vaccines as unnecessary should be taken seriously, not treated as conspiracists, he said.

“It’s a really reasonable thing to look into, and I think we should be fair to people who are confused about this and question why they need to get a vaccine when they had a documented case of Covid,” he said. “The problem is, like so many things with Covid, we just don’t know enough to make a firm decision. I think erring on the side of having people get vaccinated even if they’ve had Covid is the most prudent course.”

So far, though, no employer or government has made a vaccine-mandate exception for people who previously got sick. And broadly, the refusal to account for natural immunity has set off a firestorm in right-wing politics — both from sitting lawmakers and more bombastic candidates for office.

Sen. Rand Paul (R-Ky.), who was one of the first high-profile lawmakers to contract the coronavirus in 2020, has refused to be vaccinated on the grounds that his natural immunity makes the shots unnecessary. For weeks, Republican lawmakers in Ohio pushed a bill that would have exempted those with natural immunity from vaccine mandates, though the proposal didn’t become law. And Allen West, a GOP candidate for governor in Texas, recently doubled down on his anti-vaccine stance, arguing even while hospitalized with Covid-19 that his newfound immunity made vaccination redundant.

“Until they show me evidence that people who have already had the infection are dying in large numbers or being hospitalized or getting very sick, I just made my own personal decision that I’m not getting vaccinated because I’ve already had the disease, and I have natural immunity,” Paul said in a radio interview earlier this year.

The issue is also being litigated in court. Earlier this month, a federal judge declined to halt Michigan State University’s vaccine mandate, following a lawsuit in which a university employee argued she should be exempt because she had previously been infected with Covid-19. Separately, another federal judge ruled against a professor who sued the University of California system on the same grounds.

By and large, the Biden administration and public health officials across the country have not engaged in the natural immunity debate. Instead, they have either ignored or dismissed the claims as the country’s vaccination push continues.

To Plescia, however, ignoring the question instead of tackling it head-on represents a missed opportunity to rebuild some of the trust lost throughout the pandemic.

“This is an opportunity to get beyond some of the contentiousness,” he said. “Both sides ought to take this issue seriously. In my opinion, biologically, it would make sense that at least for a period of time, you’re going to have some immunity of the same strength as what you get from a vaccine.”

Science aside, crafting policy that allows people who’ve been sick with Covid to avoid vaccine mandates could prove impossible. For one, overwhelming evidence shows the three vaccines authorized for use in the U.S. are safe and effective, giving policymakers few compelling reasons to help Americans avoid being vaccinated.

For another, it could be difficult to prove prior infection, given the limited supply of reliable antibody tests and the fact that many people who almost certainly were sick with Covid-19 never received a diagnostic test, either. Even if people could show they have antibodies, or prove they had previously tested positive, it would be all but impossible to tell exactly how strong their immunity was, and whether it had waned.

Parmet argued that most laws cast a wide net for precisely this reason: It’s simply not practical or worthwhile for governments to write in every plausible exception, especially when there’s no compelling reason a requirement shouldn’t be enforced.

“Almost all laws sweep too broadly,” she said. “Legislatures don’t make all of the exceptions. Kids have to go to school even if they’re born geniuses, fully learned.”

Parmet continued: “Laws can’t be perfect, and they certainly can’t be perfect early in a pandemic. You can’t expect the state policy to change with every preprint. That would just be madness.”

Correction: An earlier version of this story didn’t describe the CDC study clearly. It showed that vaccination after a Covid-19 infection provided more powerful protection than immunity derived only from a previous coronavirus infection.

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