The Omicron coronavirus variant adds burden to the Hong Kong government’s zero-tolerance approach to the disease. Having far greater transmissibility than previous strains, spreading much faster globally and being more readily able to evade vaccination, any strategy has to be several steps ahead of developments. There can be no room for unscientific or knee-jerk responses; despite the uncertainties, the city has to be prepared and able to prevent outbreaks. New measures move in that direction, although given the risk and threat, more effort is obviously necessary. Authorities need to be especially vigilant and prepared with the approaching festive season and holidays. Hong Kong cannot refuse entry to residents from overseas. For that reason, Britain, popular for university education, where daily coronavirus cases are at record levels largely due to Omicron, has been added to the highest-risk category after two arriving passengers tested positive for the variant. From Friday, anyone flying to the city from any nation will need to produce a negative Covid-19 test 48 hours before boarding , a 24-hour reduction. An existing flight suspension mechanism was also tightened to ensure carriers comply with rules. Hong Kong Covid-19 adviser calls for end to aircrew quarantine ‘loophole’ But authorities are also mindful of the strain being put on the Penny’s Bay camp, the city’s highest-standard quarantine facility. Passengers from high-risk countries are taken there after arrival and required to stay and undergo daily testing before transferring to a pre-booked hotel to complete the mandatory 21 days of community isolation. Under the new rules, the time they remain there has been cut to four days from seven, the explained rationale being that all Omicron cases so far detected have been found within three days. Penny’s Bay has only 1,500 units, although two further phases providing another 2,000 rooms are being built, and there are about 500 more units in Chai Wan, Sai Kung and Pat Heung. Hong Kong’s tough anti-Covid policy and a population closely adhering to mask-wearing, cleanliness and social distancing, has ensured no local outbreaks since May. But vaccination rates are low among the elderly and a programme offering booster jabs is not expected to be expanded to the wider community until next month. Omicron, meanwhile, is spreading at an astonishing speed and rapidly taking over from Delta as the dominant variant in many countries. Until vaccines that offer protection are available, the best strategy to slow its spread is vaccination and booster shots. But maintaining a zero-tolerance strategy requires a further strengthening of guards. Potential loopholes, such as exemptions for cargo pilots, may need to be reviewed. Much is still not known about Omicron and authorities need to follow the science and be prepared.