The High Authority of Health, or HAS, said that since recovered individuals had developed an immunity response akin to a vaccine, a single shot is probably sufficient.

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“A single vaccine dose will also play the role of reminding” a previously infected person’s immune system how to fight COVID-19, the independent body said in an opinion report.

If applied, the decision is expected to speed up the pace of France’s vaccination drive. All three of the vaccines authorized for use in the European Union -- made by Pfizer, Moderna and AstraZeneca -- were developed to be administered in two doses delivered a few weeks apart.

In trial studies, a two-shot dosing schedule was shown to be the only way to increase immunity against the virus to near-full level.

France has been under fire for the slow rollout of its vaccination program. Prime Minister Jean Castex has characterized the rollout as having “a brisk pace,” and promised last week that 4 million shots -- both first and second doses — would be given this month.

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French authorities reported Thursday that over 2.1 million people had received one vaccine dose, of whom over 535,000 also got their second shot.

Researchers at New York’s Mount Sinai medical school recently began studying vaccine effects in people who’d previously had COVID-19.

The results are preliminary, posted on a website for researchers, but among 109 vaccine recipients those who’d previously been infected had 10 to 20 times higher antibody levels after the first dose of vaccine -- and retained higher levels after a second dose — than the never-infected.

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While the study is small, the Mount Sinai team concluded the findings suggest “only one dose of vaccine would not negatively impact” the previously vaccinated and offer a rationale considering policy changes.

“It’s not surprising that the natural infection worked as a primer and the first vaccine dose is a booster,” said Mount Sinai’s Dr. Viviana Simon, who coauthored the report.

Simon said it’s important that people who already had COVID-19 not skip vaccination entirely. Getting at least one dose will boost existing antibodies and broaden the spectrum of antibodies they produce, and may be especially important as virus variants circulate, she said.