‘Natural immunity’ can be dangerous — try ‘hybrid immunity’

All immunity is “natural,” Dr. Carlos Del Rio, president-elect of the Infectious Disease Society of America, told me recently on Sirius XM’s Doctor Radio. However you signal the immune system to make neutralizing antibodies, T cells and memory B cells against SARS-CoV-2 is natural, whether it’s due to encountering the virus itself or receiving a signal from a messenger RNA molecule to make the virus’s spike protein. 

Vaccines are “natural” too. 

Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, agreed with this in a subsequent interview with me for Fox News. The problem with using the term “natural immunity” isn’t just one of accuracy, it’s also the message it sends to the public — namely that one kind of immunity may be better than another.  

This can be dangerous, especially since many people may not realize that the potential long-term side effects from COVID — including loss of smell and taste, cognitive changes, and lung and heart issues — far outweigh the benefits in terms of the immunity you do develop, which appears to be temporary and variable. Though this is also true for the vaccine, as boosters are required to maximize protection, it is very clear that the side effects of the vaccine are much less than the side effects from COVID.  

In fact, a new study among young athletes who have recovered from COVID showed a 2.3 percent incidence of myocarditis. By contrast, the risk of myocarditis associated with the vaccine is extremely low — less than 5 per 100,000 for teenage males.  

The main problem with extolling natural immunity at the expense of vaccinated and boosted immunity is that it may encourage people to believe they have already had COVID even if they really didn’t. You can check people who feel they were infected for COVID antibodies, but this test can’t be used to reliably track either infection or immunity after infection. Almost every patient I have can recall a time over the past two years when they’ve had congestion, fatigue, cough, or fever that might have been COVID. If you lack those antibodies, it doesn’t mean you didn’t have COVID at some point. 

This is why I like Israel’s system of confirming COVID infection with nasal swabs or a documented positive antibody test before considering a person as immune from infection.  

But what about vaccinated immunity? A study just out from Israel, published in the New England Journal of Medicine, demonstrates a 90 percent decrease in death among those who have received Pfizer boosters. And previous studies have shown a marked decrease in severity and risk of getting COVID after being boosted (more than six months after the second vaccine). 

Is there a way to measure this response, and tell people that based on a blood test it is their time to receive a booster? The answer is no, because the spike antibody protein test measures antibodies to this protein whether they effectively neutralize the virus or not. So the test is most helpful when it is low, which is likely an indication that a boost is needed.  

Based on the data from Israel and elsewhere, I believe in boosting everyone who received a vaccine more than six months ago. At this time, the variants (Delta and especially Omicron) appear to partly evade the immune response, and re-infection from Omicron is increasing both among the vaccinated and the unvaccinated. Early data from the UK demonstrates that boosters still protect you to a large extent from Omicron. 

This is also why we can’t count on so-called “natural immunity” to protect us. I prefer instead “hybrid immunity,” meaning a recovery from COVID plus at least one MRNA vaccine. Studies show that this type of immunity may be the most substantial, and it makes sense — think of a hybrid car. The gas engine is COVID recovery, and the big battery is vaccine-induced immunity. They work together well; the “mileage” is better. 

No one should wish for COVID because the risks are real. But if you already had it, and then add a vaccine, the benefits are also very real.  

Marc Siegel, M.D., is a professor of medicine and medical director of Doctor Radio at NYU Langone Health. He is a Fox News medical correspondent and author of the new book, “COVID; the Politics of Fear and the Power of Science.”