The inoculation campaign in Turkey entered another level, as second doses of China's Sinovac COVID-19 vaccines started being administered to healthcare workers on Thursday.

The nationwide vaccination rollout started on January 14.

Nurettin Yiyit, chief physician of the Feriha Oz Emergency Hospital and Ilhan Varank Training and Research Hospital in Istanbul, said Turkey opted for a 28-day pause between the two shots as studies revealed that two doses provide better protection against the coronavirus.

A total of 4,500 people already received their first shots, and no COVID-19 case has been observed among them, the chief physician said.

(With input from Xinhua)