Four online publications linked to Russian intelligence agencies have been spreading false or misleading information about coronavirus vaccines, The Wall Street Journal reported, citing an official at the US Department of State’s Global Engagement Center.

The sites, identified as New Eastern Outlook, Oriental Review, News Front, and Rebel Inside, have emphasized the side effects of Pfizer’s coronavirus vaccine as well as other western pharma companies’ vaccines, stoking concerns about whether the vaccines are effective or had been rushed through the US approval process, the WSJ said.

The sites don’t have large audiences, but officials said their false stories are often picked up and circulated by international media. They typically focus on true news reports about rare side effects of the vaccines, but fail to provide accurate context that shows the vaccines are safe for most people. “Russian intelligence services bear direct responsibility for using these four platforms to spread propaganda and lies,” a State Department spokesman told the WSJ.

In addition to the campaign to discredit Western vaccines, Russia’s state media and Twitter accounts connected to the Russian government are also trying to boost the profile of Russia’s Sputnik V vaccine.

A spokesperson for the Kremlin denied the allegations to the WSJ.

Russia announced in November that its Sputnik V vaccine had efficacy of 90 percent, but critics said the clinical trials of the vaccine on patients were too small. However, British medical journal The Lancet reported last month that larger-scale testing had found Sputnik V was safe, and had a 91 percent efficacy rate. According to the Associated Press, as of late February only 4 million people in Russia— about 3 percent of the population— had been vaccinated.