LONDON — Several European influencers say they have been offered money to use their social media presence to discourage their millions of followers from receiving the Pfizer-BioNTech coronavirus vaccine by a suspicious agency that French officials reportedly think could be linked to Russia.

According to the influencers, they were approached online and asked to tell their large followings that the Pfizer vaccine is dangerous and has sparked more deaths than the one developed by AstraZeneca and Oxford University. The Oxford-AstraZeneca vaccine has been plausibly linked to extremely rare but in some cases fatal blood clots. European and U.S. regulators have not linked the Pfizer vaccine to any such side effects.

Taking to Twitter earlier this week, French YouTuber Léo Grasset — also known as DirtyBiology — said he had received a “strange” proposal and attached screenshots of the request, which asked him to falsely tell followers that “the mainstream media ignores” the fact that the vaccine has been linked to a high death toll. The messages informed Grasset that the agency had a “colossal budget” and that if he wanted to work with the company, he would have to hide sponsorship details from viewers.

“I received a partnership proposal, which consists of damaging the Pfizer vaccine on video,” he said, as he warned social media users that influential personalities were being targeted by conspirators who wanted to create vaccine skepticism.

The Pfizer-BioNTech vaccine ― produced by a German and an American company ― has by far been the most frequently administered coronavirus vaccine in France.

The Wall Street Journal reported Tuesday that the disinformation effort had triggered an investigation by French counterintelligence authorities, to examine whether the Russian government orchestrated it.

The French Defense and Health ministries did not immediately respond to a request for comment on Wednesday.

French Health Minister Olivier Véran said in an interview on Tuesday: “I do not know where it comes from, I do not know if it comes from France or from abroad.”

The self proclaimed public relations agency behind the offer goes by the name of Fazze and originally claimed to be based in London — although no record shows it as registered there. On its website, the agency describes itself as an “influencer marketing platform” but does not offer contact details. Its Instagram account is private, a change that was recently made, according to the Guardian.

Grasset later told his Twitter followers that those who had claimed to be employed at the company all had links to Russia, writing that the professional profiles of those in question had since vanished from LinkedIn.

Véran, France’s health minister, slammed the effort on Tuesday, calling it “dangerous” and “irresponsible.” Some influencers had been offered up to $2,450 to publish the posts, according to French media outlets.

The incident has raised concerns about more targeted disinformation campaigns, as vaccinations are finally gaining momentum in Europe and the focus of authorities may soon shift from meeting demand for vaccine shots to persuading holdouts.

France was among the world’s most vaccine-skeptical nations when coronavirus vaccines were rolled out late last year. At the time, about 60 percent of the French were not inclined to get the shots, an Ipsos survey showed.

Hoping to counter skepticism, France’s government has implemented its vaccination campaign more carefully than other countries have, insisting on time-consuming pre-vaccination consultations and a cautious interpretation of vaccine manufacturers’ guidelines.

The return to a degree of normalcy in countries that quickly vaccinated their populations, including Israel, has shifted the public debate in France in recent months. France has now partly vaccinated more than 34 percent of its population, which puts it ahead of some other European countries that had lower rates of vaccine skepticism earlier this year.

But France may remain more vulnerable to targeted disinformation campaigns than some of its neighboring countries. Officials are concerned that the country’s vaccination campaign may slow down earlier than elsewhere, as the number of new cases continues to go down and the urgency of the pandemic is somewhat fading from the public debate.

Speaking to The Washington Post earlier this year, members of France’s pro-vaccine group Les ­Vaxxeuses said the government has been too slow at actively countering online disinformation campaigns. Anti-vaccine videos have been viewed millions of times on French social media over the past year.

Meanwhile, the absence of an early and effective online government information campaign to dispel doubts meant that “the space was empty, there was no scientific discussion,” a member of the group said earlier this year, speaking on the condition of anonymity.

Other influencers — including German journalist Mirko Drotschmann, who has almost 1.5 million subscribers on YouTube, and artist Sami Ouladitto — said they were targeted with requests to discredit the Pfizer vaccine.

Earlier this month, Drotschmann tweeted he had been asked to join an online “information campaign,” with organizers inviting him to share supposedly leaked documents about deaths after Pfizer-BioNTech vaccinations. He told his followers the chief executive of the company appeared to be based in Moscow, but he did not name the company or people who had contacted him.

Although it is being used in multiple countries, Russia’s Sputnik V vaccine has yet to receive approval from the European Union’s medicines agency, which officials say is the result of a lack of adequate information. Last month, Brazil’s Health Regulatory Agency rejected the vaccine, listing significant safety concerns that include a lack of quality control and an absence of details regarding the vaccine’s side effects.

Kremlin spokesman Dmitry Peskov said that Russia was willing to give Brazil additional data if required.

Noack reported from Paris.

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