The European Union drug regulator approved the Johnson & Johnson vaccine on Thursday, amid mounting frustration with a sluggish inoculation campaign, hobbled by supply shocks and logistics failures, and with global wars over scarce doses ratcheting up.

The Johnson & Johnson vaccine, which can be stored in regular fridges for up to three months and only requires one shot, is the fourth to be approved by the European Medicines Agency, Europe’s main drug regulator. It was approved for people over 18. Three more vaccines, Novavax, CureVac and Sputnik V are undergoing a rolling review by the regulator, the initial stage of the process that would eventually grant them authorization for use in Europe.

The European Commission, the bloc’s executive arm, is expected to officially authorize the use of the shot later on Thursday, opening the door for the arrival of a contracted 200 million doses, and to an option for another 200 million, which could help speed up the underwhelming vaccination rollout on the continent.

The bloc, which is home to about 450 million people in 27 countries, has so far inoculated only 6.5 percent of its inhabitants, lagging behind the likes of Britain, Israel and the United States.

But the first batches of Johnson & Johnson vaccine are not expected before next month, complicating hopes for a quick fix.

The bloc has been fending off double-edged criticism since the beginning of the vaccination campaign. The commission, which has taken the lead in ordering and approving the vaccines on behalf of its 27 members, has been blamed for the slow pace of authorization, distribution and administration of the shots by national governments.

At the same time, accusations that Europe was engaged in “vaccine nationalism” and protectionism picked up last week after Italy blocked a small shipment of Oxford-AstraZeneca vaccines to Australia, making use of an E.U. regulation empowering its members to block exports of any doses if the manufacturer has not yet met its supply obligations to the bloc.

But according to internal documents, seen by The New York Times, the European Union exported 34 million doses of coronavirus vaccines in recent weeks, making it an export powerhouse even as it battled supply shortages at home.