The woman was said to have received both doses of the Covid vaccine on February 19 and March 19 respectively, although the type of vaccine she received remains unknown.

She had stayed at a subdivided unit at Fu Yung Building in Tsuen Wan for home quarantine after she returned to the city.

Health officials said the woman may either be a local case or an imported case, as she could have contracted the virus on the mainland or have been infected by residents who stayed in the same flat as her.

Four types of Covid vaccines are currently available in mainland China, including two Chinese-made vaccines produced by Sinopharm and Sinovac.

Sinopharm announced on December 30 last year that phase three trials of the vaccine showed that it was 79 percent effective at preventing infections 2 weeks after people received the second dose.

While the coronavirus vaccine developed by China's Sinovac has been found to be 50.4% effective in Brazilian clinical trials, according to the latest results released by researchers.