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People Who Have Had Covid Should Get Single Vaccine Dose, Studies Suggest

New studies show that one shot of a vaccine can greatly amplify antibody levels in those who have recovered from the coronavirus.

At least 30 million people in the United States — and probably many others whose illnesses were never diagnosed — have been infected with the coronavirus so far. Should these people still be vaccinated?

Two new studies answer that question with an emphatic yes.

In fact, the research suggests that for these people just one dose of the vaccine is enough to turbocharge their antibodies and destroy the coronavirus — and even some more infectious variants.

“I think it’s a really strong rationale for why people who were previously infected with Covid should be getting the vaccine,” said Jennifer Gommerman, an immunologist at the University of Toronto who was not involved in the new research.

A person’s immune response to a natural infection is highly variable. Most people make copious amounts of antibodies that persist for many months. But some people who had mild symptoms or no symptoms of Covid-19 produce few antibodies, which quickly fall to undetectable levels.

The vaccines “even the playing field,” Dr. Gommerman said, so that anyone who has recovered from Covid-19 produces enough antibodies to protect against the virus.

Flush with antibodies, samples from all of the participants could neutralize not only B.1.351, but also the coronavirus that caused the SARS epidemic in 2003.

In fact, the antibodies seemed to perform better than those in people who had not had Covid and had received two doses of a vaccine. Multiple studies have suggested that the Pfizer-BioNTech and Moderna vaccines are about five times less effective against the variant.

Blood taken about two to three weeks after vaccination showed a significant jump in the amounts of antibodies compared with the samples collected before vaccination. The researchers don’t yet know how long the increased amount of antibodies will persist, but “hopefully, they’ll last a long time,” Dr. McGuire said.

The researchers also saw increases in immune cells that remember and fight the virus, Dr. McGuire said. “It looks pretty clear that we’re boosting their pre-existing immunity,” he said.

In that study, most people had been infected with the coronavirus eight or nine months earlier, but saw their antibodies increase by a hundredfold to a thousandfold when given the first dose of a vaccine. After the second dose, however, the antibody levels did not increase any further.

“It’s a real testament to the strength of the immunologic memory that they get a single dose and have a huge increase,” said Dr. Mark J. Mulligan, director of the N.Y.U. Langone Vaccine Center and the study’s lead author.

In some parts of the world, including the United States, a significant minority of the population has already been infected, Dr. Mulligan noted. “They definitely should be vaccinated,” he said.

It’s unclear whether the thousandfold spike in antibody levels recorded in the lab will occur in real-life settings. Still, the research shows that a single shot is enough to increase the levels of antibodies significantly, said Florian Krammer, an immunologist at the Icahn School of Medicine at Mount Sinai in New York.

“If you put all four papers together, that’s providing pretty good information about people who already had an infection only needing one vaccination,” Dr. Krammer said.

He and other researchers are trying to persuade scientists at the Centers for Disease Control and Prevention to recommend only one dose for those who have recovered from Covid-19.

Ideally, those people should be monitored after the first shot in case their antibody levels plummet after some weeks or months, said Dennis R. Burton, an immunologist at the Scripps Research Institute in La Jolla, Calif.

The fact that the supercharged antibodies observed in the new study can fight the 2003 SARS virus suggests that a single dose of the vaccine may have prompted the volunteers’ bodies to produce “broadly neutralizing antibodies” — immune molecules capable of attacking a broad range of related viruses, Dr. Burton said.

He and other scientists have for decades investigated whether broadly neutralizing antibodies can tackle multiple versions of H.I.V. at once. H.I.V. mutates faster than any other virus and quickly evades most antibodies.

Without such a vaccine, scientists will need to tweak the vaccines every time the virus changes significantly. “You’re stuck in a kind of Whac-a-Mole approach,” he said. It will probably take many months if not longer to develop and test that sort of vaccine against the coronavirus, but “that’s the longer-term way to approach this virus.”

Category: Science

Source: New York Times

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