HONG KONG - The Hong Kong government on Monday (Aug 16) said it would tighten quarantine rules from Friday (Aug 20) for travellers from 16 countries.

Fifteen of them - Bangladesh, Cambodia, France, Greece, Iran, Malaysia, the Netherlands, Spain, Sri Lanka, Switzerland, Tanzania, Thailand, Turkey, the United Arab Emirates and the United States - will be specified as high-risk places from the current medium-risk classification.

Only Hong Kong residents who are fully vaccinated can enter the city if they are from high-risk places. Besides having to present a negative test result for Covid-19 before boarding the flight, they will also have to be in quarantine for 21 days and self-monitor for another seven days.

Australia, which is now in the low-risk category, will be re-classified as medium risk. Singapore is also included in this category.

The quarantine requirements for medium and low-risk categories remain unchanged.

For residents and visitors who are inoculated and are returning from medium-risk places, they have to undergo a 14-day quarantine, besides showing a negative test result before the flight. Residents who are not vaccinated will have to go through 21 days of quarantine.

As for those who have been fully vaccinated and have a positive serology antibody test result conducted by a laboratory recognised by the Hong Kong government, mandatory quarantine is seven days, with another seven days of self-monitoring.

Following the latest review, New Zealand will be the only place listed as low-risk and mandatory quarantine for travellers who are fully vaccinated will be seven days.

The recalibration comes after the Hong Kong panel on the pandemic reviewed the quarantine rules on Monday.

Government advisers - microbiologist Ho Pak Leung and respiratory medicine specialist David Hui - had both urged officials to relook the shorter quarantine periods for vaccinated individuals entering Hong Kong.

Associate Professor Ho of the University of Hong Kong on Monday told local media that the decision created a "loophole" in the city's defence against Covid-19. His gripe was that the US was listed as a medium-risk place even though the pandemic there had rebounded for about a month.

In one recent case, a fully vaccinated domestic helper who returned to Hong Kong from the US served seven days of quarantine, even though she tested positive for antibodies.

The 38-year-old woman then tested positive for the highly infectious Delta variant on Aug 14, a week after completing the mandatory hotel quarantine.

The woman had received two doses of the BioNTech vaccine in Hong Kong in April and left for the US on June 18 and returned on Aug 1.

She visited some places in Stanley Plaza, Wan Chai and Happy Valley and testing orders have been issued.

On Monday, the health authorities said there were three new confirmed cases, all of which were imported. This brings the total tally of Covid-19 cases to more than 12,000, with 212 deaths so far.