Marty Makary is a professor at the Johns Hopkins University School of Medicine and Bloomberg School of Public Health. He is editor in chief of Medpage Today and author of “The Price We Pay.”

As thousands of Americans perish daily due to covid-19 and the nation scrambles to ration a scarce vaccine supply, many Americans are appropriately asking: “Should I get the vaccine if I already had covid-19?” The Centers for Disease Control and Prevention says yes, with a narrow exception for those who have been infected in the past 90 days and received convalescent plasma or antibody therapy.

But this is outdated and fails to take natural immunity seriously. As a result of this flawed guidance, Americans with natural immunity — including many who are low-risk — are inappropriately getting the vaccine instead of high-risk seniors.

Many medical experts have been dismissive of natural immunity due to prior infection, but there is overwhelming data showing that covid-19 reinfections are rare, and when they do occur, the infection is often mild. A Public Health England study released last week found that less than 1 percent of 6,614 people who tested positive for covid-19 antibodies developed a reinfection within the five months studied.

That’s because the immune system works. Having the infection activates both antibodies as well as memory B- and T-cells, which teach your immune system to recognize the same virus in the future to swiftly eradicate it.

Natural immunity after covid-19 infection appears to last for at least the one year in which the virus has been circulating at large. Extrapolating from research on the SARS and MERS coronaviruses, it could be much longer. In one study of 176 people infected with SARS, immunity lasted for an average of two years. Another long-term analysis of health-care workers previously infected with SARS found antibodies up to 12 years later. Protective antibodies for the MERS coronavirus have similarly been documented to last for at least three years. And while the 1918 pandemic was caused by an influenza virus, the immune systems of those infected were able to make antibodies to the virus nearly nine decades later, a 2008 Nature study found.

Even mild infections appear to elicit a persistent and functional immune response. One recent European study found that people who had mild or asymptomatic covid-19 mounted a “robust T-cell immunity” afterward. A separate French study affirmed this, noting that some people who lived with a confirmed covid-infected person developed T-cell immunity even when they did not test positive for covid.

These scientific observations and the growing prevalence of natural immunity in the United States have significant implications for our national vaccine strategy. To maximally preserve human life, we should prioritize our limited vaccine supply to those who have never had covid-19. Given the scarcity of the vaccine, it doesn’t make sense to administer it to those who already had the disease while vulnerable seniors are sitting ducks in this pandemic war.

Many in the medical field have been playing down natural immunity. In the noble effort to overcome vaccine hesitancy, they argue that everyone should get the vaccine to reach herd immunity and reopen society. But we need to stick to the science. Let me be clear: I believe the vaccine is safe and strongly recommend that we vaccinate all Americans, but doing so is not a requirement to achieve herd immunity. Given that close to a third of all Americans and perhaps more have had covid-19 infections, it’s possible that herd immunity is closer than we think.

It is important to note that most experts predict that vaccinated immunity will probably last longer than natural immunity due to prior infection — a finding true of several other vaccines. But there is no clinical data to support that hypothesis, and expert predictions are not always correct. In fact, a few of my Johns Hopkins colleagues have suggested that natural immunity due to prior infection could be better than vaccinated immunity, pointing to the approximately 5 percent of infections in the Pfizer-BioNTech and Moderna trials that occurred in people who received the vaccine. While getting the vaccine is far safer than getting the infection, it is entirely possible that the chances of infection for those vaccinated is similar to those who contracted the virus previously. Time will tell.

Personally, I side with the scientists who predict that vaccinated immunity will last longer than natural immunity, but let’s let science and not opinion answer that question. For those scientists who insist that vaccinated immunity is the only true immunity, I would remind them that there is absolutely zero data on covid-19 vaccine immunity after 300 days.

Given the scarcity of the lifesaving vaccine and the urgency for vulnerable Americans to get it quickly, people who had the infection should step aside and go to the back of the vaccine line. We lost more than 100,000 nursing home residents and staff to covid-19 last year, and 80 percent of all deaths have been in people 65 and older. The vaccine is currently a scarce resource. If we ration it wisely, we will save more lives and get back to normal life faster.

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