Why Doesn't the U.S. Account for Natural Immunity?

Key TakeawaysSome data suggests that someone who’s recovered from COVID-19 may be as protected against future infection as a vaccinated individual.Verifying infections and counting them among an individual’s vaccine doses may be too logistically complicated at this point in the pandemic.Public health leaders maintain that vaccination is the best way to be protected against the virus.

Key Takeaways

Some data suggests that someone who’s recovered from COVID-19 may be as protected against future infection as a vaccinated individual.Verifying infections and counting them among an individual’s vaccine doses may be too logistically complicated at this point in the pandemic.Public health leaders maintain that vaccination is the best way to be protected against the virus.

From the early days of the COVID-19 vaccine rollout, the question of whether a prior infection should count as equivalent to a dose of vaccine has emerged and re-emerged in both scientific and political circles.

Countries like Israel, Canada, and the United Kingdom consider a past infection to count towards an individual’s immunity status. Some experts have also pointed tomounting evidencethat immune protection from natural infection is at least as protective as vaccination.

But in the United States, immunity status solely hinges on vaccination. There’s no spot on the vaccine card to indicate recovery from a prior infection. Many institutions and employers require workers, students, or visitors to be fully vaccinated and sometimes boosted. In its attempts to bolster vaccination rates, the White House has repeatedly expressed frustrationwith those who refuse the shot.

Still, many people in the U.S. are on their way to developinghybrid immunity, or the combined immunity from vaccination and infection.

As the number of recovered people increases and data continues to emerge on the durability of natural immunity, should the U.S. consider people to be immune or non-immune, rather than vaccinated or unvaccinated?

Peter Chin-Hong, MD, professor of infectious diseases at University of California, San Francisco, said that vaccines are standardized and more reliable than natural immunity.

“We know what’s going to happen based on the experience of now millions of vaccinated people and thousands in the trials, which are really rigorously controlled,” Chin-Hong told Verywell.

The Case for Considering Natural Immunity

The CDC maintains that people should get a COVID-19 vaccine regardless of prior infection, saying thatthe level of protection from natural immunity may vary based on the severity of their illness, age, and the time since their infection. The CDC says, “No currently available test can reliably determine if a person is protected from infection.”

In discussions about immunity, the focus tends to fall on the importance of antibodies. Meanwhile, memory T and B cells areoften overlooked. Once these virus-fighting cells are primed to recognize an invader—either through vaccination or infection—they can rouse a defense against subsequent viral infections.

After the body has successfully fought off an infection, it is natural for antibodies to clear from the blood. T and B cells linger for months, and sometimes years, longer, ready to make new antibodies and attack future antigens.

A study published in the journalSciencein 2021 indicated that antibodies stayed relatively stable for at least sixmonths after COVID-19 infections, and participants had more virus-specific B cells at six months post-infection than after one month.

In an investigative piece published inThe BMJ, some experts argued that natural immunity should be considered equally protective as vaccine-based immunity.

While such data emphasizes the capability of the human immune system, experts warn that COVID-19 infections come with great risk.

Surging Omicron cases prompted many to question whether it’s best to just “get it over with.”Paul Goepfert, MD, professor of medicine and microbiology and director of the Alabama Vaccine Research Clinic, said this is a dangerous approach that could lead to more hospitalizations and fatalities.

“You don’t want people to go out and get infected thinking that’s the way they’re going to get protected,” Goepfert told Verywell. “You’re going to get a lot of people who are going to get really sick that way and some will die.”

Plus, there’s little data on how well infection with one variant, like Delta, protects against other variants.

Immune Response Varies Among Naturally Infected Individuals

The caveat with natural immunity is that not all infections stimulate the immune system equally.

In general, the severity of an illness determines someone’s antibody levels. For instance, a person who has a high-grade fever for several days likely produces more antibodies to the virus than someone who only experiences a scratchy throat.

But that’s not always the case, Goepfert said. In a recent study, Goepfert’s team found that 36% of the participants who tested positive for COVID-19 developed little to no antibodies, despite having symptoms during their course of infection.

“I know a lot of people are testing their antibodies after they become infected and say, ‘well, I’ve got these antibodies, therefore I’m fine.’ But we know that that’s not necessarily the case,” Goepfert said.

A large number of antibodies is key for a good immune response, but scientists don’t yet have an easy way to judge the level of antibodies a person requires to be protected from severe outcomes of infection.

Plus, antibody levels are just one piece of the puzzle. Knowing an individual’s T and B cell levels could provide key information about their immune protection against reinfection. One study of symptomatic and asymptomatic COVID-19 cases found similar levels of T cells in both groups, even when antibodies waned.

However, testing for T cells can be difficult—there’s currently only one commercially available test.

Since immune responses to infection can be so disparate and antibody tests are relatively inaccessible, health officials continue to tout vaccination as the most sure-fire way to strengthen one’s immune system against COVID-19.

The vaccines have been proven again and again to be highly effective at preventing severe outcomes of COVID-19 and greatly minimize the risk of infection and transmission.

Timing Is Important

For a vaccine or infection to best stimulate the immune system, there must be a period of rest where the antibodies can clear from the bloodstream. When a new dose of antigen is introduced, immune cells are roused again and get another practice run at defending the body against the attacker.

Chin-Hong, who specializes in infectious diseases, said that “the more times you remind the immune system of the enemy, the better it’s going to perform in the future.”

The CDC said people are eligible to receive a booster shot five or more months after completing their primary regimen. The vaccination and booster schedule was designed to bolster the immune system around the time when most people’s antibody levels decline.

For instance, a person who received a two-dose regimen per the normal schedule may become infected a month after their second dose. In that case, their antibody levels may not have had a chance to wane and reactivate, meaning that individual doesn’t get much of a boost.

If an individual is infected later—say six months after the second shot—Goepfert said they might wait until the next surge to get a boost.

While it’snot unsafeto get a booster shot soon after recovering from COVID-19, some experience more severe side effects and the vaccine’s effectiveness may be diminished.

“You can’t continue to be activated to the same thing over and over again—your body has sort of defense mechanisms or regulatory mechanisms that go against that,” Goepfert said.

But Chin-Hong recommends not to wait for more than three months after recovery to get a booster dose. Recovery from COVID-19 could only be considered equivalent to one dose of vaccine, or possibly less. Someone who had a natural infection, but no vaccination, isn’t likely protected against reinfection or fromtransmitting the virusto their community, he added.

An Already Complicated Rollout

U.S. health officials made vaccine-focused recommendations and mandates, opting for vetted inoculations over antibody testing or accepting PCR test results as proof of immunization.

“Are we equipped as a system to understand and to verify documented infections? We probably could if we wanted to. It may just be logistically easier to look at a card and see a lot number, date, and vaccine to verify exposure,” Chin-Hong said.

With the spread of Omicron and possible future emergence of other variants, easy-to-edit mRNA vaccines may be key to a more targeted immunization approach than natural immunity can provide. Pfizer, Moderna, and Johnson & Johnson are developingOmicron-specific vaccines. Pfizer said it began phase one clinical trials last week.

“The vaccine can sort of keep up with variants moving forward, but natural immunity cannot,” Goepfert said.

Hybrid Immunity May Help in the Long Term

Both at a personal level and within a larger population, hybrid immunity—the combination of natural and vaccine-induced immunity—is the “holy grail” of an immune response, Chin-Hong said.

With the high case rates in the U.S., a majority of the population likely has some degree of natural immunity to COVID-19. Coupled with relatively large vaccination coverage, the country is well on its way to developing a hybrid immune system.

In the future, when the diseasebecomes endemic, Chin-Hong said showing some documentation of prior infection or antibody status might be enough to demonstrate immunity.

“My prediction is, we’re going to descend very rapidly from Omicron and the country and hopefully the world will have a lot more immunity. The dust will settle and then people will feel more relaxed about loosening some of what immunity means,” Chin-Hong said.

Until then, he said, “we want to maximally protect people in the best way we know how.”

What This Means For YouExperts warn against intentionally getting sick with COVID-19, which can lead to severe short- and long-term health outcomes. Being vaccinated and receiving a booster is the best way to protect yourself and others from the disease.

What This Means For You

Experts warn against intentionally getting sick with COVID-19, which can lead to severe short- and long-term health outcomes. Being vaccinated and receiving a booster is the best way to protect yourself and others from the disease.

8 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention:Estimated COVID-19 burden.Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063Gazit S, Shlezinger R, Perez G, et al.Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections.MedRxiv.Preprint posted online August 25, 2021. doi:10.1101/2021.08.24.21262415Goldberg Y, Mandel M, Woodbridge Y, et al.Protection of previous SARS-CoV-2 infection is similar to that of BNT162b2 vaccine protection: a three-month nationwide experience from Israel.MedRxiv.Preprint posted online April 24, 2021. doi:10.1101/2021.04.20.21255670Pulliam JRC, van Schalkwyk C, Govender N, et al.Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa.MedRxiv.Preprint posted online December 2, 2021. doi:10.1101/2021.11.11.21266068Liu W, Russell RM, Bibollet-Ruche F, et al.Predictors of nonseroconversion after SARS-CoV-2 infection.Emerg Infect Dis. 2021;27(9):2454-2458. doi:10.3201/eid2709.211042Le Bert N, Clapham HE, Tan AT, et al.Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection.J Exp Med.2021;218(5):e20202617. doi:10.1084/jem.20202617Mathioudakis AG, Ghrew M, Ustianowski A, et al.Self-reported real-world safety and reactogenicity of COVID-19 vaccines: a vaccine recipient survey.Life (Basel). 2021;11(3):249. doi:10.3390/life11030249

8 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention:Estimated COVID-19 burden.Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063Gazit S, Shlezinger R, Perez G, et al.Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections.MedRxiv.Preprint posted online August 25, 2021. doi:10.1101/2021.08.24.21262415Goldberg Y, Mandel M, Woodbridge Y, et al.Protection of previous SARS-CoV-2 infection is similar to that of BNT162b2 vaccine protection: a three-month nationwide experience from Israel.MedRxiv.Preprint posted online April 24, 2021. doi:10.1101/2021.04.20.21255670Pulliam JRC, van Schalkwyk C, Govender N, et al.Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa.MedRxiv.Preprint posted online December 2, 2021. doi:10.1101/2021.11.11.21266068Liu W, Russell RM, Bibollet-Ruche F, et al.Predictors of nonseroconversion after SARS-CoV-2 infection.Emerg Infect Dis. 2021;27(9):2454-2458. doi:10.3201/eid2709.211042Le Bert N, Clapham HE, Tan AT, et al.Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection.J Exp Med.2021;218(5):e20202617. doi:10.1084/jem.20202617Mathioudakis AG, Ghrew M, Ustianowski A, et al.Self-reported real-world safety and reactogenicity of COVID-19 vaccines: a vaccine recipient survey.Life (Basel). 2021;11(3):249. doi:10.3390/life11030249

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Centers for Disease Control and Prevention:Estimated COVID-19 burden.Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063Gazit S, Shlezinger R, Perez G, et al.Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections.MedRxiv.Preprint posted online August 25, 2021. doi:10.1101/2021.08.24.21262415Goldberg Y, Mandel M, Woodbridge Y, et al.Protection of previous SARS-CoV-2 infection is similar to that of BNT162b2 vaccine protection: a three-month nationwide experience from Israel.MedRxiv.Preprint posted online April 24, 2021. doi:10.1101/2021.04.20.21255670Pulliam JRC, van Schalkwyk C, Govender N, et al.Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa.MedRxiv.Preprint posted online December 2, 2021. doi:10.1101/2021.11.11.21266068Liu W, Russell RM, Bibollet-Ruche F, et al.Predictors of nonseroconversion after SARS-CoV-2 infection.Emerg Infect Dis. 2021;27(9):2454-2458. doi:10.3201/eid2709.211042Le Bert N, Clapham HE, Tan AT, et al.Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection.J Exp Med.2021;218(5):e20202617. doi:10.1084/jem.20202617Mathioudakis AG, Ghrew M, Ustianowski A, et al.Self-reported real-world safety and reactogenicity of COVID-19 vaccines: a vaccine recipient survey.Life (Basel). 2021;11(3):249. doi:10.3390/life11030249

Centers for Disease Control and Prevention:Estimated COVID-19 burden.

Dan JM, Mateus J, Kato Y, et al.Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection.Science. 2021;371(6529):eabf4063. doi:10.1126/science.abf4063

Gazit S, Shlezinger R, Perez G, et al.Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections.MedRxiv.Preprint posted online August 25, 2021. doi:10.1101/2021.08.24.21262415

Goldberg Y, Mandel M, Woodbridge Y, et al.Protection of previous SARS-CoV-2 infection is similar to that of BNT162b2 vaccine protection: a three-month nationwide experience from Israel.MedRxiv.Preprint posted online April 24, 2021. doi:10.1101/2021.04.20.21255670

Pulliam JRC, van Schalkwyk C, Govender N, et al.Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa.MedRxiv.Preprint posted online December 2, 2021. doi:10.1101/2021.11.11.21266068

Liu W, Russell RM, Bibollet-Ruche F, et al.Predictors of nonseroconversion after SARS-CoV-2 infection.Emerg Infect Dis. 2021;27(9):2454-2458. doi:10.3201/eid2709.211042

Le Bert N, Clapham HE, Tan AT, et al.Highly functional virus-specific cellular immune response in asymptomatic SARS-CoV-2 infection.J Exp Med.2021;218(5):e20202617. doi:10.1084/jem.20202617

Mathioudakis AG, Ghrew M, Ustianowski A, et al.Self-reported real-world safety and reactogenicity of COVID-19 vaccines: a vaccine recipient survey.Life (Basel). 2021;11(3):249. doi:10.3390/life11030249

Meet Our Medical Expert Board

Share Feedback

Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit

Was this page helpful?

Thanks for your feedback!

What is your feedback?OtherHelpfulReport an ErrorSubmit

What is your feedback?