Single injection of Pfizer vaccine offers strong protection to those who have had Covid-19, British studies show



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In the United States, the vaccine is licensed in two doses 21 days apart. To protect yourself from Covid-19, the first dose triggers the immune system and the second stimulates it.

The researchers found that in those who had previously had a natural infection, the vaccination increased their antibody levels by more than 140 times. “This increase appears to be at least an order of magnitude greater than that reported after a conventional first-aid vaccination strategy in previously uninfected individuals,” the researchers wrote in their article.

The other article, written by researchers at Imperial College London and other UK institutions, included data on 72 healthcare workers vaccinated at the end of December. Twenty-one of them had evidence of a previous coronavirus infection.

Workers provided blood samples upon receipt of their first dose and then 21-25 days after vaccination. The researchers found that people with a previous coronavirus infection appeared to generate stronger immune responses to a dose of the vaccine compared to those who had not been infected previously.

Dr Paul Offit, director of the Vaccine Education Center at Children’s Hospital in Philadelphia, told CNN on Friday that the results of the two new papers were not surprising.

“What this data shows is exactly what you would expect – that people who have been naturally infected, who have already developed an immune response to this virus, when given that first dose without a quote, have a booster response. , “Offit said. “In other words, they act like they’re getting the second dose.”

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But for now, Offit has stressed that people who have already recovered from Covid-19 are recommended to continue receiving both doses of the vaccine when it is their turn.

“You could reasonably ask, ‘Well, given that there is a vaccine shortage, why not make this recommendation that anyone who has ever been infected can reasonably be given a dose, period?’ I think the reason that didn’t happen was largely programmatic, ”Offit said.

“If you were to try to superimpose the current strategy of getting people vaccinated – that there was a screening test in advance to see who had already been exposed and who had not – it would make it much more difficult to deployment of this vaccine. So people just thought, look, give everybody the vaccine, ”Offit said. “There is no downside. Worst case to worst case, you will only get booster responses when you are vaccinated if you have been naturally infected before.”

Offit added: “If you have never been infected with this virus before, this second dose of mRNA vaccine greatly boosts your immunity to T cells, dramatically increases your antibody response and will undoubtedly give more complete and lasting protection. “

It is possible that a single dose of the coronavirus vaccine will be sufficient to protect people who have recovered from an episode of Covid-19, said Dr Francis Collins, director of the United States National Institutes of Health on Thursday. .

“It seems that in these individuals, a single dose is basically a booster for them because they already had the infection. They already have antibodies which may be sufficient and they may not need to. the second dose, ”Collins told CNN Chief Medical Correspondent Dr. Sanjay Gupta.

Collins said the NIH “is trying to collect as much data as possible on this subject at this time.”

But, he said a single dose strategy for everyone could have unintended consequences.

“Are these people between the first and the second really ducks for getting infected?” Collins asked. “Is this really a way to encourage more mutations to occur because they are only partially protected? The virus has a chance to live in its system a little longer and take some changes.”

Collins said that until data shows otherwise, the two doses allowed three to four weeks apart is the regimen to follow.

CNN’s Nadia Kounang contributed to this report.

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