A recent House Bill (H.R. 5590) and its Senate companion (S. 2846), both titled the “Natural Immunity is Real Act”, would require all federal agencies issuing rules or regulations relating to COVID-19 to

acknowledge, accept, agree to truthfully present, and incorporate, the consideration of natural immunity as it pertains to COVID–19 with respect to the individuals subject to the applicable regulations.

As the bill helpfully explains, natural immunity means “immunity that is naturally existing”. Natural immunity, of course, sounds so much more pleasant and less scary than the CDC’s term: “infection-induced immunity”.

The sponsor of H.R. 5590, Rep. Diana Harshbarger (R-TN), appears to believe the evidence on natural immunity is settled and one’s level of immunity can be both accurately determined and used as an indication of sufficient protection from the SARS-CoV-2 virus. Per her press release:

I introduced this bill today because the Biden Administration must ‘follow the science’ and be open, honest and transparent about the millions of Americans who have natural immunity against the COVID-19 virus . . . . There’s ample scientific evidence from numerous peer-reviewed studies that natural immunity from previous COVID-19 infection is effective, durable and long-lasting.

According to a Tennessee TV station, Rep. Harshbarger thinks that unvaccinated individuals could submit blood samples for antibody testing and, if antibodies are found, they should not be subject to any vaccine mandate.

Some of the House bill’s co-sponsors, all fellow Republicans, seem to share her confidence that natural immunity can be measured accurately and that its effectiveness against the virus is settled. Rep. Daniel Webster (R-FL) charges that:

Too many medical leaders [whom he accuses of “denying science”] are refusing to publicly recognize what overwhelming data has already shown – protection afforded to individuals with natural immunity is real, robust and durable.

Rep. Chris Stewart’s (R-UT) comments suggest a belief that infection-induced and vaccine-induced immunity are equivalent:

The vaccine offers effective protection against COVID-19; natural immunity offers effective protection against COVID-19.

And, from Rep. Bill Posey (R-FL):

No American should be forced to choose between getting the COVID vaccine or keeping their job, particularly when the Biden policy fails to recognize that millions of Americans have immunity because they’ve already had and recovered from COVID.

On the other hand, at least one co-sponsor, Rep. Jeff Van Drew (R-NJ), acknowledges the science is not as settled as his colleagues make it out to be:

We know vaccines work, but natural immunity could be equally or similarly as effective in certain individuals. If the CDC would devote time into its research, we would have robust, evidence-based research that could help America finally move on from this virus.

In fact, the CDC has done just that, as you’ll see in a moment.

Indeed, the “numerous peer-reviewed studies” linked in Rep. Harshbarger’s comment, which is actually a letter from Republican MDs and other health care professionals in Congress to CDC Director Dr. Rochelle Walensky, takes a more nuanced approach. Although the letter cherry-picks the studies it cites supporting natural immunity’s effectiveness against the virus, it also admits that the evidence is not all in:

. . . we urge the CDC to harness available data and technology to . . . truly determine an individual’s level of protection against COVID-19. It may be the case that it is not medically necessary for an individual to receive a vaccination. It may also be the case that a sufficient level of protection may be produced from one dose.

Rep. Harshbarger is not anti-vaccination but is emphatically anti-vaccine mandate. She is a Pharm.D who admirably, considering the enormous resistance to COVID-19 vaccination in her party, made a “get vaccinated” Public Service Announcement, although in it she firmly states that the decision is up to the individual. She’s also introduced bills prohibiting vaccine mandates and “passports“.

That is not to say the anti-vaccination forces aren’t delighted with the opportunity presented by the Natural Immunity is Real Act to further their cause. The execrable National Vaccine Information Center “news” outlet, The Vaccination Reaction (such a cute name!), which earlier this year ran a reprint of an American Institute for Economic Research (AIER) article questioning why mainstream medicine was “downplaying or erasing natural immunity”, touted the bill. The AIER, a libertarian think tank, has promoted “in essence, letting COVID-19 rip through the ‘healthy’ population in order to achieve ‘natural herd immunity'”. As SBM’s Dr. David Gorski explained in his post on the subject, “natural immunity” is a long-time anti-vaccine trope resurrected for COVID-19.

Other co-sponsors of the bill have not been shy about their anti-vaccination sympathies. Rep. Mo Brooks (R-AL) pushed anti-vaccine talking points in a letter to President Biden. Rep. Madison Cawthorn (R-NC) saw a prelude to confiscation of guns and Bibles in a proposed door-to-door immunization drive. Rep. Marjorie Taylor Greene (R-GA) also pushed misinformation about COVID-19 vaccines, saying falsely that the vaccines were “failing” and were ineffective in reducing the spread of the virus. Rep. Lauren Boebert (R-CO) called researchers studying low vaccination rates “Needle Nazis” and spread vaccine misinformation, including continuing to refer to approved vaccines as “experimental”. And, prior to the pandemic, Rep. Mark Green (R- TN), an MD, and Rep. Bill Posey (R-FL) gave credence to the widely discredited (mainly because it never existed in the first place) vaccine-autism connection.

Meanwhile, back at the CDC . . .

Health experts have pushed back against the proposed law. Kenneth Goodman, director of the University of Miami Miller School of Medicine Institute for Bioethics and Health Policy and the Florida Bioethics Network, told the Orlando Sentinel that it is

bad science, dangerous policy and saddest of all, ideology tricked out as ethics . . .

And in response to Rep. Daniel Webster’s claim to another Orlando news outlet that the bill is “just saying there are other options than just a vaccine”, pediatric pulmonologist Dr. Akinyemi Ajayi pointed out that, while there is some natural immunity protection acquired from an infection, it is not clear how long it lasts and that a verifiable way to determine natural immunity does not currently exist.

An associate professor of medicine in the Division of Infectious Diseases at University of Utah Health made similar points in a Deseret News article about the proposed law:

While there is some evidence natural infection provides strong immunity, there is variability from person to person and less predictability than vaccine immunity . . . . Clinical antibody tests available also are not great correlates of immunity to COVID-19 and have wide variability from test to test.

Meanwhile, it appears that the CDC has been doing pretty much what the proposed law dictates all along, only not with the result its backers would likely prefer. On Oct. 29, 2021, the CDC published a Science Brief titled “SARS-CoV-2 Infection-induced and Vaccine-induced Immunity”, an overview of the current scientific evidence regarding infection-induced and vaccine-induced immunity, including both peer-reviewed and preprint publications, as well as unpublished CDC data. In a signal that the CDC will continue to “consider” natural immunity, the report says that “new data continue to emerge, and recommendations will be updated periodically”.

Key findings include:

  • Fully vaccinated and previously infected individuals both have a low risk of subsequent infection for at least 6 months.
  • We don’t have sufficient data to determine an antibody titer threshold indicating when an individual is protected from infection and no FDA-authorized test can reliably determine whether a person is protected.
  • There is a wide range of antibody titers from infection but vaccines (especially mRNA vaccines) typically lead to a more consistent and higher-titer initial antibody response.
  • More quality evidence exists regarding vaccine-acquired than infection-induced immunity and, in fact, there is not enough evidence to apply what we know about the latter to children and those with a mild or asymptomatic infections.
  • Vaccination after infection significantly enhances protection and further reduces risk of reinfection.

Thus, the CDC continues to recommend COVID-19 vaccination for all eligible persons, including those who have been previously infected.

On the same day, the CDC issued a Morbidity and Mortality Weekly Report Early Release, a study showing that COVID-19 was over five times more common among hospitalized people who were unvaccinated and had a previous infection, compared with those who were fully vaccinated and hadn’t had COVID-19 before. The study concluded that

All eligible persons should be vaccinated against COVID-19 as soon as possible, including unvaccinated persons previously infected with SARS-CoV-2.

Although, technically, the bill (should it become law) would not apply to the CDC’s report or study (because neither is a rule or regulation), it sure looks to me like the CDC has acknowledged, accepted, and truthfully presented natural immunity and incorporated it into its recommendations.

Funny that the Representatives and Senators supporting the Act didn’t take the time to ring the federal agency most responsible for COVID research and policy and ask them whether they were “considering” natural immunity before blasting the Biden Administration for failing to “follow the science” and introducing legislation on October 18, 2021, a mere 11 days before the CDC’s report and study came out. We can safely assume that neither was done in less than two weeks, so obviously both were ongoing projects when Rep. Harshbarger’s press release was issued and the bills introduced.

I can’t find that any of the bills’ sponsors have responded to the report or study. Then again, I wonder if it matters to them. I suspect the House and Senate bills were just a bit of political theater, designed to play to political bases. If they really cared about “following the science”, one would think they would have hailed the CDC’s recent publications as within the spirit of their proposed legislation and urged constituents to follow the CDC’s recommendations. But, of course, they didn’t, because it doesn’t fit their anti-mandate or anti-vaccination narrative. The Act was an act all along.

UPDATE: In a special session called by Gov. Ron DeSantis, the Florida Legislature just passed, and DeSantis signed, a new law:

businesses are required to exempt employees from a [that is, the federal] mandatory vaccination policy if they have Covid immunity from prior infection, are tested periodically for the virus or choose to wear personal protective equipment provided by the company.

‘We recognize people who have natural immunity,’ DeSantis said. “Whatever a private employer wants to do, you’re automatically exempt because of natural immunity.’

Here’s the actual language of the new law regarding “natural immunity”:

To claim an exemption based on COVID-19 immunity, the employee must present to the employer an exemption statement demonstrating competent medical evidence that the employee has immunity to COVID-19, documented by the results of a valid laboratory test performed on the employee. The Department of Health shall adopt a standard for demonstrating competent medical evidence of such immunity.

This should be interesting, considering that Florida’s new Surgeon General and head of the state health department drafting the standard is Dr. Joseph Ladapo, a member of the kook anti-vaccine  America’s Frontline Doctors (or maybe former member, to my knowledge he hasn’t said one way or another). Stay tuned.



  • Jann J. Bellamy is a Florida attorney and lives in Tallahassee. She is one of the founders and Board members of the Society for Science-Based Medicine (SfSBM) dedicated to providing accurate information about CAM and advocating for state and federal laws that incorporate a science-based standard for all health care practitioners. She tracks state and federal bills that would allow pseudoscience in health care for the SfSBM website.  Her posts are archived here.    

Posted by Jann Bellamy

Jann J. Bellamy is a Florida attorney and lives in Tallahassee. She is one of the founders and Board members of the Society for Science-Based Medicine (SfSBM) dedicated to providing accurate information about CAM and advocating for state and federal laws that incorporate a science-based standard for all health care practitioners. She tracks state and federal bills that would allow pseudoscience in health care for the SfSBM website.  Her posts are archived here.