"Arrivals coming from the mainland should receive three vaccination jabs and undergo five days of rapid antigen tests," suggested the University of Hong Kong's virologist Jin Dongyan on Monday.

Jin said opening the border will not bring another pandemic outbreak, given the city has prepared to cope with the disease. However, he advised the government to monitor the situation for at least a week in the initial phase before further relaxing the headcounts of inbound travellers.

"I believe that a one-week adapting period will be sufficient to reflect the impact that may be caused to the public health system," Jin said.

Joseph Tsang Kay-yan, co-chairman of the Medical Association's advisory committee on communicable diseases, agreed with Jin's opinion. He added that the testing requirement for overseas and mainland visitors should be unified to cope with potential surging Covid cases.

"Commuters travelling between the two places should present negative results of their nucleic acid tests, within 24 hours, before their journey. It will reduce the risk to a significant extent if arrivals are required to undergo five-consecutive-day rapid tests," Tsang pointed out.

"Priority to travel should be given to the commuters with urgent needs," said Allen Shi Lop-tak, president of the Chinese Manufacturers' Association of Hong Kong.

He hoped that the daily quota for business sectors in the first phase of quarantine-free travel could be set as 5,000 to 6,000 and gradually increase.