The United States announced last week that it would soon open its doors to foreign travelers vaccinated against the coronavirus, loosening restrictions for broad swaths of global visitors for the first time since the pandemic began.

But the new rules, set to take effect in November, appear to also shut out many people who consider themselves to be fully immunized — including millions who have received two doses of Russia’s Sputnik V vaccine.

Hundreds of thousands of Russians could be directly affected. Despite frosty diplomatic relations and limited demand for international travel, roughly 300,000 Russians visited the United States in 2019, the last year for which figures are available, according to the U.S. Travel Association.

More broadly, the U.S. plan is another blow for the manufacturers of Sputnik V, which Moscow has proudly proclaimed as the first coronavirus vaccine to be registered for use. Though the vaccine was intended to be a powerful tool of pandemic diplomacy, its limited acceptance abroad and slow rates of delivery have left it behind not only Western vaccines but also those made by Chinese manufacturers.

“This is a big problem for Russian travelers and for people in other countries who’ve received Sputnik V,” Judyth Twigg, a professor at Virginia Commonwealth University who tracks public health in Russia, said of the new U.S. rules in an email.

The Russian Direct Investment Fund, the sovereign wealth fund that backed Sputnik V, said in a statement that not only has the vaccine “been approved in 70 countries where over 4 billion people, or over half of the world’s population, live, but its efficacy and safety have been confirmed both during clinical trials and over the course of real-world use in a number of countries.”

“We stand against attempts to politicize the global fight against COVID-19 and discriminate against effective vaccines for short-term political or economic gains,” the statement continued.

The new U.S. plan requires that most noncitizens seeking entry to the United States are vaccinated with shots approved for emergency use either by the U.S. Food and Drug Administration or the World Health Organization. That includes vaccines made by Pfizer and Moderna, as well as shots developed by Chinese firms such as Sinopharm and Sinovac.