The latest case involves a 49-year-old woman who flew in from the United States on Tuesday.
The Centre for Health Protection said the patient carried the L452R mutant strain, but did not show any symptoms.
The woman has been fully vaccinated. She received her first BioNTech jab on March 10, and a second dose on April 6.
The centre also reported fewer than five preliminary positive Covid cases.
In total, the city has recorded 11,971 Covid infections since the start of the pandemic.
Health authorities said Hong Kong had reported 25 cases over the past 14 days – 24 of them were imported while one was linked to an imported case.