Within 30 minutes of Hong Kong reversing its seven-day quarantine policy, Ovolo Hotels’ switchboard was swamped with calls.

The operator of two facilities in the city’s mandatory quarantine program also received more than 850 emails, as frantic travelers sought to adjust their bookings.

Hong Kong’s about-face — 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.