The European Union drug regulator announced on Thursday that it was beginning a rolling review of the Russian-developed Sputnik V vaccine, after one of the bloc’s members moved unilaterally to use the shots and another is about to do the same.

The announcement by the regulator, the European Medicines Agency, comes amid a slow and frustrating vaccine rollout in the European Union that has been dogged by supply disappointments as well as major logistical problems.

The review is the formal process the agency uses, in which scientists examine data on the shots’ efficacy and side effects — it is the fastest way to examine the vaccine as a whole, with a view to eventually granting it authorization for use in the European Union.

The agency said in a news statement that the Gamaleya Research Institute, which developed the vaccine, had applied for the rolling review through a Germany-based entity named R-Pharm Germany.

Hungary broke with the bloc and ordered its own share of Sputnik V vaccines this year, granting the shots authorization locally through its national regulator. As the supply woes in the European Union began to bite, the Czech Republic this month announced it would follow suit. A deal to acquire the Russian vaccine has also set off a political crisis in Slovakia.

Several other European governments were considering a similar move, despite the fact that Ursula von der Leyen, president of the European Commission, the bloc’s executive arm, recently cast doubt on the Sputnik V vaccine.

“We still wonder why Russia is offering theoretically millions of millions of doses while not sufficiently progressing in vaccinating their own people,” Ms. von der Leyen said during a news conference last month.

“This is also a question I think that should be answered,” she added. “They have to submit the whole set of data, indeed go through the whole scrutiny process like any other vaccine.”

While the announcement of the review is an important step in the formal scientific scrutiny by the European regulator, there is no telling how long the process will take. The agency will require deep access to data underlying the vaccine’s performance, as well as site visits to its production facilities, before granting authorization.