The Hong Kong government yesterday said it would tighten quarantine rules from Friday for travelers 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, up from their current medium-risk classification.

Only Hong Kong residents who are fully vaccinated can enter the city from high-risk places. Besides having to present a negative test result for Covid-19 before boarding their flight, they will 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 in this category.

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

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

As for those who are fully vaccinated and have a positive serology antibody test result from 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 yesterday. Government advisers - microbiologist Ho Pak Leung and respiratory medicine specialist David Hui - had both urged officials to relook the shorter quarantine for vaccinated individuals entering Hong Kong.