HONG KONG • Hong Kong's about-face on its seven-day quarantine policy - coming less than two months after it eased one of the world's toughest Covid-19 border regimes - is upending travel plans and causing chaos for hotels just weeks before the start of the school year and the end of the summer vacation period.

Triggered, officials say, by growing concern about the Delta variant, Tuesday's reversal saw the scrapping of a new rule that allowed vaccinated residents returning from medium-risk locations to quarantine in a hotel for just one week - half the typically required time.

The day before, countries including the United States, Spain and France were classed as high risk, requiring people arriving from those countries to serve a longer quarantine stay of 21 days.

Hotels serving as quarantine facilities were flooded with calls. Some callers needed to extend their bookings, while others wanted to cancel their entire reservation, said Mr Sonesh Mool, operations manager of Ovolo hotel. The suddenness of the changes make it more challenging, he added.

"It will be like playing Tetris as we're running at 90 per cent occupancy from August to October. It's proven very difficult to serve guests with swift and timely adjustments, especially when hundreds of requests, e-mails and calls come flooding."

The shift is reigniting criticism of Hong Kong's approach to reopening, which has been split between trying to restore some semblance of its global connectivity and keeping Covid-19 cases at near-zero, the only way to reopen the border with China.

With infections limited over the past few months and the vaccination roll-out progressing, this week's changes came as a surprise and have been slammed as regressive by business groups.

They also come as Singapore - Hong Kong's regional rival - eyes plans to resume some travel links as soon as next month.

Unlike other places with a similar closed-border, zero-tolerance approach such as China, Australia and New Zealand, Hong Kong's government does not allocate quarantine hotel rooms to incoming travellers.

Instead, it is a free-for-all, with individuals responsible for securing their own rooms and hotels free to set their own pricing. That means that sudden shifts in policy result in a scramble, with some people unable to board their flights because they cannot secure an adequate booking.

The move "creates disruptions for almost everyone returning from Europe, no matter what your category is", said Mr Frederik Gollob, chairman of the European Chamber of Commerce in Hong Kong. The situation is "a mess" and "everyone running hotel operations in Hong Kong is freaking out right now. Everyone has to change their own arrangements", he added.​

The average booking rate at designated quarantine hotels for next month - before the changes were announced - is around 70 per cent, said the city's Food and Health Bureau on Tuesday.

The impact of the tightened curbs remains to be seen, the government department said.

"We will continue to closely monitor the demand for hotel rooms and consider the need for releasing some 1,500 reserve rooms in individual quarantine hotels, if and where necessary," it said.

With Hong Kong increasingly intertwined with China, Chief Executive Carrie Lam has been laser focused on trying to reopen the border. Before the pandemic, Chinese tourists were one of the city's biggest sources of revenue, and the removal of quarantines on both sides would allow a resumption of business flows.

But Beijing has given little indication of a pathway to easing border curbs and China is in the midst of a virus resurgence, ignited by the Delta variant slipping through its own tight controls.

Mr Mathew Phan booked a flight from Hong Kong to the US just four days before Monday's shift deeming 15 countries high risk. The financial analyst now faces three weeks locked in a hotel room when he returns from the US, where he is due to attend a course in October.

He echoed the anger felt by many over the unexpected changes, which lit up Facebook and other social media groups created to negotiate the complicated quarantine system.

"Super annoying," said Mr Phan, 40. "If this policy is just because they were just trying to manage a statistic, that would just be stupid."

BLOOMBERG