Hong Kong’s desire to reboot its coronavirus-ravaged tourism sector by forming air travel bubbles with seven overseas destinations could prove difficult to get off the ground, with control of the pandemic, the pace of vaccination and the choice of vaccines varying across countries.

With the fourth wave of Covid-19 showing signs of abating in Hong Kong and a vaccination drive under way, Secretary for Commerce and Economic Development Edward Yau Tang-wah revealed on Monday the government had sent a new proposal to Singapore to restore a planned travel bubble while writing to six other countries about resuming talks on such plans.

A source familiar with the matter said on Tuesday the proposal touched on Hongkongers being vaccinated as a condition for joining the travel bubble scheme, a unilateral suggestion pending the Singapore government’s input.

Hong Kong leader Carrie Lam Cheng Yuet-ngor said on Tuesday morning she had told her officials to look into the arrangements needed for bilateral travel.

“Of course, vaccination will facilitate the resumption of travel to a certain extent, but I’m sure you realise that when we talk about travelling, it’s a bilateral thing,” she said, adding that it was also up to the other side to ease entry for Hongkongers.

Whether vaccination would be mandatory to travel out of Hong Kong would be for the receiving side to decide, she said. If partners such as Singapore wanted Hongkongers to be inoculated before they could enter the city state, Lam said, she would have to tell residents.

With a travel-bubble mechanism between Singapore and Hong Kong in place since November last year and inoculation campaigns under way in both places, travel experts said the city state was a front-runner over other potential countries such as Japan, South Korea, Australia, New Zealand, Thailand and Vietnam.