The developers of Russia’s Sputnik V coronavirus vaccine have repeatedly failed to provide data that regulators deem to be standard requirements of the drug approval process, according to five people with knowledge of European efforts to assess the drug, providing new insight into the country’s struggle to win foreign acceptance of its product.

Reuters reported last month that the European Medicines Agency (EMA)’s review of the drug’s safety and efficacy was delayed because a June 10 deadline to submit data on the vaccine's clinical trials was missed, according to one of those people, who is close to the agency, and another person familiar with the matter. The EMA is the European Union’s medicines watchdog.

The hitches go beyond that one deadline, the person close to the agency said. As of early June, the EMA had received hardly any manufacturing data, and the clinical data the agency had received was incomplete, the person said.