Health officials on Sunday reported three new imported Covid-19 cases.
One of them was a 38-year-old man who arrived from the Philippines.
He earlier received two doses of the BioNTech vaccine in Hong Kong and tested positive for antibodies in July.
The two other patients both flew in from Qatar and both were fully vaccinated against Covid-19.
None of them had developed any symptoms.
Meanwhile, the Centre for Health Protection has ordered people who stayed at Block K of Kornhill in Quarry Bay to undergo tests, after a 16-year-old boy tested positive after he travelled from the SAR to the United Kingdom.
The boy received two doses of BioNTech jabs in Hong Kong in July, landed in the UK on September 6 and tested positive there on September 16.