Post-infection immunity may be an odd topic for political strife, but it touches on the mandate of a COVID vaccine and that those who have been infected should be exempted. Some observers have implied that US policy is ignoring some scientific evidence. But science is much more complex and unstable than that. The relevant question is not whether natural immunity exists, but if it is just as protective and lasts as long as the vaccine-induced type. The studies gave conflicting answers. The situation is now changing again, as the BA.2 version has started to take over. It’s still considered an Omicron, but it looks wildly different from its flagship BA.1 version.
In May 2020, scientists confirmed that a Sars-CoV-2 infection creates some immunity, based on a study published in Science led by Dan Baruch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center . Vaccines work by fooling the body as if it has been infected, so they work best against diseases where post-infection immunity is strong and permanent, he told me, such as measles, mumps and rubella. . It has not worked for HIV, a virus that attacks the immune system and cannot be cleared except in rare cases. With COVID, the antibodies deplete over time. This may reduce immunity, as may be the case with newer variants. With the original version, it seemed that the vaccines provided better protection against becoming infected. But during the delta boom, some studies showed that the reversal had taken place. New data released by the Centers for Disease Control (CDC) shows that previous infections gave people better protection against delta than one or two shots of a vaccine. But it was best to get vaccinated apart from getting infected. The booster also restored most of the vaccine effectiveness.
“There was an initial belief that vaccination is better than natural infection—and many people still think that will be the case.” “But I think it’s more nuanced now, and a lot of people think natural immunity gives you an adequate level of protection.” But how much, compared to a Covid jab? “It is not clear.” Barouch agrees with many others that a confirmed COVID infection could probably substitute for a shot.
Before vaccines were developed, scientists told me that as with other viral infections, vaccines are sometimes more protective than previous infections and sometimes less. One reason vaccines work better is that viruses often disable a person’s immune response as part of their survival strategy. This is happening with Sars-CoV-2, some studies show, said Shiv Pillai, a professor of immunology at Harvard Medical School. The disadvantage of COVID jabs is that they are only designed to produce antibodies that attack just one part of the virus—the spike protein. As it varies, jabs lose some efficacy. Being infected can give people a wide variety of protections. It seems absurd for anyone trying to get infected for protection, but it is possible that some people may try if they are averse to a vaccine, and the infection could satisfy a vaccine mandate or passport system. Vaccines are much safer than getting viruses, but not everyone thinks clearly.
O’Micron’s massive mutation changed the game. Jabs still protect us from serious disease, but neither vaccination nor infection with an earlier version provides much protection against a mild omicron infection. Eric Topol, professor of medicine at Scripps Research, pieced together a number of studies and pointed out that most studies comparing jabs with previous infections involved the original variant, or delta. But Omicron dominates and the new BA.2 version is forcing us to recalculate. Barouch has led some trials on how well BA.2 slips away from previous infections or protection from vaccines. “It’s a little bad, but not a ton worse,” he told me. Omicron appears to protect against infection to some extent against BA.2, so experts say it is unlikely to cause a large-scale wave of infection. But there are many other unforeseen things that can happen – good or bad – with this ever-changing pandemic.
Policy decisions about vaccine mandates can be informed but not determined by science. Those decisions depend on the ethics and legitimacy of the jab mandate and whether living without vaccination harms society by reducing transmission or health resources. In addition to the policy, severely immune-compromised people are already being advised to get a second booster in the US, but others are not. But that may change if there is a new wave or fresh evidence that immunity is declining. A past transition may play into that decision.
Such decisions depend on what new variants will emerge in the future, ongoing research on the duration of immunity, and whether scientists eventually develop a more variant-proof coronavirus vaccine. The last two years may have passed slowly, but we are still battling a new disease and there is much to learn.
Faye Flamm is a Bloomberg Opinion columnist and host of the podcast ‘Follow the Science’.
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