The Centers for Disease Control and Prevention is under increased pressure from epidemiologists to acknowledge mounting evidence regarding the immune-boosting power of recovery from prior COVID-19 infection.
Evidence that recovery from COVID-19 elicits a long-lasting antibody response has mounted over the past two years. Still, the CDC has not recognized it as a means of gaining protection against severe illness. A growing cache of scientific studies has shown that people with prior infections are significantly protected, even more so when combined with vaccination, creating “hybrid immunity.”
“The data comparing natural infection versus vaccine-induced immunity has been mixed, but I think it is clear that both certainly confer a very meaningful level of protection against reinfection. And I think we should be acknowledging this as a public health community that it’s not just the vaccine that builds up our immunity, but it’s also infection,” said Dr. David Dowdy, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.
Infectious disease researchers have amassed considerable evidence to support the immune system-bolstering power of recent recovery from infection combined with vaccination.
In a January report from the CDC, researchers found that protection from previous infection alone proved to be durable and highly effective against reinfection caused by the delta variant, the dominant strain circulating throughout the United States until December 2021.
Scientists have known for a while that immunity to the virus from infection or vaccination wanes over time, so those researching levels of immunity must consider time since getting the shots or recovering from the disease.
“When you’re talking about protection against getting infected, even if it’s like a mild infection, that has to do much more with the timing of exposure. It doesn’t matter if you’ve gotten three exposures a year ago. You would then now be very susceptible to getting infected again,” Dowdy said.
The protection afforded by recovery from infection is particularly relevant concerning vaccine mandates.
The Biden administration has imposed vaccine mandates for federal workers and healthcare workers employed by companies that receive federal funds from the Centers for Medicare and Medicaid Services. The mandates, which did not allow for recognition of immunity conferred by infection, were an attempt to boost lagging vaccination rates and prevent workers from getting seriously ill but drove many workers to the exits.
The healthcare industry staffing shortage, already dire before the pandemic, was exacerbated when many hospitals and nursing homes across the U.S. were made to require vaccinations. As a result, the shortage has become so acute that an estimated 1.2 million additional nurses are needed to address the coming waves of the coronavirus.
Still, natural immunity on its own does not provide reliable protection for everyone, as varying degrees of illness in different people cause variations in antibody responses, according to Dr. Gabor Kelen, an emergency medicine physician at the Johns Hopkins Bloomberg School of Public Health.
“We know natural immunity from infection is very variable in and of itself. We also know that boosters and the vaccine itself have a much more uniform and robust response that natural immunity may or may not confer,” Kelen said. “We’re not quite there yet, but it’s not like we can ignore that this could be an appropriate way to think about things.”
The CDC has avoided indicating that it will consider recovery from COVID-19 as a viable way to gain protection from getting sick again. Director Rochelle Walensky has maintained that vaccinating the vast majority of the population is the surefire way to beat the pandemic. The bulk of the agency’s studies has argued that unvaccinated people are at higher risk of being hospitalized or dying due to COVID-19.
The CDC’s report in January was among the few times that the agency released data on reinfections. Researchers reported that cases caused by the delta variant in unvaccinated people who had recovered from COVID-19 were sevenfold lower in California and nearly tenfold lower in New York compared to case rates in people who have not been vaccinated or recovered from infection. The report also said unvaccinated people who recovered from a previous infection were better protected against a COVID-19 diagnosis than people who were immunized alone.
President Joe Biden’s chief medical adviser, Dr. Anthony Fauci, has struggled to articulate a clear assessment of natural immunity. In response to a question of whether various studies proved that infected people were as well protected as those who have been vaccinated, Fauci said on CNN last September that “there could be an argument” that they are.
“I don’t have a really firm answer for you on that,” Fauci said. “That’s something that we’re going to have to discuss regarding the durability of the response.”
Republicans in Congress have pressed the Biden administration for nearly a year to recognize the protection potency of recent recovery from infection. Most vociferous among them have been Sen. Rand Paul and Rep. Thomas Massie, both from Kentucky. In a May 2021 statement, Paul said, “To dictate that a person recovered from COVID-19 with natural immunity also submit to a vaccine — without scientific evidence — is nothing more than hubris.”
Around the same time, Massie said that vaccines “provoke your body into providing a natural immune response — the natural immune response that a prior COVID infection also elicits. To deny the effectiveness of the natural immune response is to deny the basis of the vaccine.”
Any changes to how the CDC sees COVID-19 will require careful, clearly laid out policy changes. The last thing the Biden administration would want is for scores of unvaccinated people to get infected purposely as an alternative to getting the shots.
“Particularly those that are vaccine-hesitant may get sucked into the notion of ‘this isn’t very important anymore if I get infected’ and ‘I’m done, I don’t need a booster,'” Kelen said. “There are some very, very serious complications in people who wind up in a hospital and some very long-term impacts. So it’s not quite as trivial as ‘I’ll go get infected.'”
“Getting sick so that you don’t get sick doesn’t make a lot of sense, especially for people who have not been vaccinated and actually still are therefore fairly vulnerable if they’ve never been infected before,” Dowdy said. “On one hand, we need to acknowledge that both infection and vaccination provide protection against future illness while also not encouraging people to intentionally get sick and recognizing that policies around using previous infection as a substitute for vaccination have some problems.”
The CDC and the Department of Health and Human Services did not respond to requests for comment.
