U.S. officials said the Russians, through intelligence agencies, have launched a campaign to undermine confidence in COVID vaccines, such as Pfizer Inc.'s and other Western vaccines.

The campaign includes the use of online publications that have questioned the vaccines' development and safety in recent months, according to U.S. officials.

One official of the State Department's Global Engagement Center official identified four publications that have served as fronts for Russian intelligence agencies, Wallstreet Journal reported.

The websites pressed the vaccines' risk of side effects, questioned their efficacy, and further claimed that the U.S. had rushed the Pfizer vaccine through the approval process, among other false claims.

U.S. officials said the outlets' readership is small. However, they noted that they insert false narratives that Russian and international media can amplify.

The Global Engagement Center official said they could say that these sites behind the disinformation campaign are directly linked to Russian intelligence services, adding that they are all foreign-owned located outside the U.S.

"They vary a lot in their reach, their tone, their audience, but they're all part of the Russian propaganda and disinformation ecosystem," the official said in the report.

Russian state media and Russian government Twitter accounts have also taken part in raising concerns about the price and safety of the Pfizer vaccine. Experts outside the U.S. government noted that this is an effort to promote Russia's Sputnik V COVID vaccine's sale.

The U.S. officials said the Russian intelligence agencies have been working to undermine public confidence in Western COVID vaccines for months, Daily Mail reported.

READ MORE: Venezuela to Use Russian, Chinese Coronavirus Vaccines

Russian Outlets

Two of the outlets, namely New Eastern Outlook and Oriental Review, are allegedly controlled by Russia's foreign intelligence service, the SVR.

The U.S. official said these outlets depicted themselves as academic publications and targeted their commentary on the U.S. at audiences in the Middle East, Africa, and Asia.

Another outlet named News Front is reportedly guided by Russia's Federal Security Service, the Soviet-era KGB's successor agency. The said outlet releases content in 10 languages and had about nine million page visits between February and April of last year, according to the official.

Last fall, the U.S. State Department indicated that the News Front had ties to Russian secret services and was funded by the Kremlin.

COVID Vaccine Passports

Meanwhile, the European Union's authority is considering a digital pass that would allow European citizens who have received a COVID vaccine to travel for work or tourism.

Ursula von der Leyen, president of the European Commission, said in a tweet that the goal of the "Digital Green Pass" is to provide proof that a person has been vaccinated, as well as information on COVID-19 recovery, according to a Time report.

Several private sectors and non-government digital health passports are already being rolled out, including the International Air Transport Association Travel pass made for IATA travelers. Another one is CommonPass, which The Commons Project Foundation developed.

READ ALSO: US Says No to Russia's Offer to Help With COVID-19 Vaccine

WATCH: Russia Claims Sputnik V COVID Vaccine is 95% Effective - From CBC News: The National