A child arrives at a school during the COVID-19 pandemic in Bucharest, Romania, Feb. 8, 2021. (Photo: Xinhua)

The COVID-19 variant first identified in Britain was confirmed in 15 out of the 28 regions in Bulgaria, the country's Health Ministry said in a statement on Monday.

The strain was proven in laboratories in Bulgaria and Germany, the ministry said.

But the coronavirus variants that were first detected in South Africa, Brazil and Nigeria have not been confirmed in Bulgaria, the ministry said.

A total of 260,308 COVID-19 cases have been confirmed in Bulgaria so far, and the country's death toll stood at 10,614, according to the ministry.

The variant first identified in Britain was confirmed in Bulgaria for the first time on Jan. 22 this year.

As the world is struggling to contain the pandemic, vaccination is underway in an increasing number of countries with the already-authorized coronavirus vaccines.

Meanwhile, 261 candidate vaccines are still being developed worldwide -- 79 of them in clinical trials -- in countries including Germany, China, Russia, Britain, and the United States, according to information released by the World Health Organization on March 5.