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Business News/ Opinion / Columns/  New covid variants pose fresh riddles for vaccine mandates
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New covid variants pose fresh riddles for vaccine mandates

Levels of immunity granted by jabs versus infection keep shifting

Sars-Cov-2 has been evolving to evade both natural and jabbed immunity (Photo: AFP)Premium
Sars-Cov-2 has been evolving to evade both natural and jabbed immunity (Photo: AFP)

Post-infection immunity might be a strange topic for political strife, but it touches on covid vaccine mandates and whether those who have been infected should be exempt. Some observers have implied that US policy has been ignoring some scientific evidence. But the science is more complicated and unsettled than that. The relevant question isn’t whether natural immunity exists, but if it’s as protective and lasts as long as the vaccine-induced kind. Studies gave conflicting answers. The situation is now changing again, as the BA.2 variant is starting to take over. It’s still considered Omicron, but it looks wildly different from its dominant BA.1 version.

In May 2020, scientists confirmed that a Sars-CoV-2 infection creates some immunity, based in part on a study published in Science, led by Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center. Vaccines work by fooling the body into acting as if it’s been infected, so they work best against diseases where post-infection immunity is strong and lasting, he told me, such as measles, mumps and rubella. It hasn’t worked for HIV, a virus that attacks the immune system and can’t be cleared except in rare cases. With covid, antibodies wane over time. That can reduce immunity, as can new variants. With the original variant, it looked like vaccines gave better protection than getting infected. But during the Delta surge, some studies showed that had reversed. New data released by the Centers for Disease Control (CDC) show that a previous infection gave people better protection against Delta than either one or two shots of a vaccine. But getting vaccinated in addition to getting infected did best. Boosters also restored most vaccine effectiveness.

“There was an early perception that vaccination is hands down better than natural infection—and a lot of people still feel that will be the case," Barouch said. “But I think it’s more nuanced now, and a lot of people think natural immunity gives you a substantial level of protection." But how much, compared to a covid jab? “That’s not clear." Barouch agrees with many others that a confirmed covid infection could probably substitute for a single shot.

Before vaccines were developed, scientists told me that with other viral infections, vaccines are sometimes more protective than past infection and sometimes less so. One reason vaccines can work better is that viruses often disable a person’s immune response as part of their survival strategy. That’s happening with Sars-CoV-2, show some studies, said Shiv Pillai, a professor of immunology at Harvard Medical School. The disadvantage of covid jabs is that they are designed to only produce antibodies that attack just one part of the virus—the spike protein. As this keeps mutating, jabs lose some efficacy. Getting infected might provide people with broader, multi-variant protection. It seems absurd for anyone to try to get infected for safety, but it’s possible some people might try if they’re avidly anti-vaccine, and infection could satisfy a vaccine mandate or passport system. Vaccines are vastly safer than getting the virus, but not everyone thinks clearly.

Omicron’s heavy mutations changed the game. Jabs still save us from severe disease, but neither vaccination nor infection with an earlier variant offers much protection against a mild Omicron infection. Eric Topol, professor of medicine at Scripps Research, tied together a lot of studies and points out that most studies comparing jabs with past infection involved the original variant or Delta. But Omicron is dominant and the new BA.2 version is forcing us to recalculate yet again. Barouch has led some tests of how well BA.2 slips by defences from past infection or vaccines. “It’s slightly worse, but not a tonne worse," he told me. It looks like Omicron infection protects to an extent against BA.2, so experts say it’s unlikely to lead to a massive infection wave. But there are scores of other unexpected things that could 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 legality of jab mandates and whether staying unvaccinated harms society by spurring transmission or depleting health resources. Policy aside, severely immune-compromised people are already being advised to get a second booster in the US, but not others. But that might change if there’s a new wave or fresh evidence that immunity is fading. A past infection might play into that decision.

Such decisions hinge on which new variants 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 gone by slowly, but we’re still dealing with a new disease and there’s a lot yet to learn.

Faye Flam is a Bloomberg Opinion columnist and host of the podcast ‘Follow the Science’.

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Published: 23 Feb 2022, 10:20 PM IST
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