Tuesday, March 21, 2023
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Covid versus vaccine immunity — data on Pfizer shot kicks up great debate again

New data shows CDC erred in telling people that vaccine-induced immunity is better than that acquired from infection. But point of vaccine is to cut risk of infection in the first place.

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People who don’t want to get vaccinated will grasp at any new piece of information to justify their reluctance — the latest being some pretty good data suggesting that the natural immunity left after recovering from Covid-19 is stronger over the long run than immunity generated by the Pfizer vaccine. It’s a finding that’s worth taking seriously — several scientists sent the study to me or mentioned it, and a number of others noted its importance in a news story in Science Magazine.

That’s a terrible reason to skip the vaccine — 100% of people who have “natural immunity” suffered from at least one bout of the disease, putting them at risk of severe illness, lingering symptoms and the prospect of spreading the virus to others. The point of the vaccine, after all, is to cut back on the risk of getting sick at all and to reduce the severity of symptoms if a so-called breakthrough occurs.

But there’s still a lot to be learned, and a lot of public-health policy that should be subject to adjustment. The new data, which come out of Israel, show that the U.S. Centers for Disease Control erred by telling people in early August that vaccine-induced immunity is better than immunity acquired from past infection. People who had two Pfizer shots were about 27 times more likely to get symptomatic Covid-19 and eight times more likely to be hospitalized than were people who’d been infected. In previous columns, I’d quoted scientists citing that earlier data, saying that vaccine-induced immunity might be better than protection from a past infection. I was wrong, and stand corrected.

While not officially published, a scientific paper announcing the new data has impressed the medical community because it’s based on a study of tens of thousands of people conducted this summer when the delta variant was dominant, and because the researchers measured what matters most: whether people got sick or were hospitalized, not just whether their antibodies changed or some tiny amount of virus was detected in their noses.

The new findings might force a rethinking of the current U.S. policy of recommending full vaccination to people who’ve already had a documented case of Covid-19. And, while it still makes sense to encourage anyone who hasn’t had the virus to get the shots, doctors might want to reconsider whether the Moderna version would be a better bet. Several studies, including one out of the Mayo Clinic, show it might offer more durable protection against the delta variant.

The immunity from infection may explain, in part, why the delta wave has leveled off or started to drop in Arkansas, Missouri, Mississippi, Louisiana and Florida, where it had risen highest. The phenomenon also complicates the study of long-term vaccine efficacy because unvaccinated people are becoming increasingly immune as delta spreads through them. That means the unvaccinated are becoming inadvertently inoculated, though at the high cost of putting pressure on hospitals and killing people.

That natural immunity works isn’t a surprise. In the summer of 2020, scary stories about waning post-infection immunity were dampening hopes that vaccines would work — as the persistence of immunity was taken as a sign that the same effect could occur with a vaccine.

Since last December, I’ve asked different experts how natural immunity might compare with vaccine-induced immunity, and it turns out that for some diseases, vaccines can be more protective than past infection. But not always.

The reason I kept asking was that people who’ve had Covid-19 wondered whether the risk-benefit ratio of getting the shots might be different for them. Last December, nobody knew whether vaccine-induced immunity would be better than infection-induced immunity, but it was always understood that past infection incurred some degree of protection.

The answer I got last December was that it was too important to get all the health-care workers vaccinated quickly. There was an emergency, the risks of the shots looked minimal, and it would have been slow and cumbersome to determine who had actually had the virus. It’s also not clear whether all the so-called asymptomatic cases elicited immunity or whether the body’s first lines of defense killed the virus off before any antibodies were created. It’s also likely that at least a few people who were never tested just assume they’ve had Covid-19, and others may have had a false positive test.

But now, perhaps the sensible approach is the one taken in France, Germany, Italy and other countries — to offer people who’ve been infected a single dose of a two-shot vaccine. Data from some previous studies as well as conclusions drawn from the Israeli data show that a single shot can boost post-infection immunity to even higher levels. Other studies suggest that a previous infection combined with a single-dose vaccine will be better than vaccines alone at protecting against new variants.

The findings may or may not figure into the policy of President Joe Biden’s administration to encourage booster shots, which has already been widely criticized for not “following the science.” Most decisions about the pandemic have had to be made with only partial knowledge, so it’s only natural that policies have to change as more relevant data become available. –Bloomberg

Also read: Delta, booster shots mean Covid vaccines could become a viable business. And that’s a problem


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