Negotiations between Hong Kong and Singapore over their much-delayed travel bubble are being hobbled by disagreements over antibody tests and vaccination rules against Covid-19 , the Post has learned. Sources familiar with the discussions on Tuesday said it was proposed that a unilateral decision by Hong Kong to require all of its residents to have had two doses of a Covid-19 vaccine at least a fortnight before departure be extended to Singaporeans. Under the bubble, travellers from both cities would need to be fully inoculated, but the two governments have not agreed on vaccination rules. Another obstacle was a plan by Hong Kong to impose antibody tests on inbound travellers, one source revealed. The Hong Kong government attempted to partially align the bubble with a recent initiative to tie antibody levels to shorter mandatory quarantine periods for all incoming visitors. Spikes in coronavirus cases twice delayed the much-awaited travel corridor, in November last year and then in May, but the recent hold-up is over the stumbling blocks. “There are some sticking points,” the source said. “For example, the Singapore public regards the antibody test as intravenous and are less receptive to it.” Both sides agreed to give it their best shot to ensure the travel bubble took off. But an insider said there were no plans for an announcement yet. Tests link Hong Kong airport worker’s Covid-19 infection to four Russian cases A source working on the travel arrangement at Hong Kong’s Cathay Pacific Airways also said the team had not been told about any announcement. Also complicating matters is Singapore’s intention to shift away from seeking to achieve zero cases and towards treating Covid-19 as endemic, as it becomes increasingly apparent that there is no credible route to eliminating the virus completely. Under this new approach, the city state will rely on vaccinations, frequent testing, and the use of new and effective therapeutic drugs as a basis for reopening its economy and allowing for quarantine-free travel. The health ministry will also pivot away from reporting daily Covid-19 infection numbers, and focus instead on trends and the number of severely ill people, similar to how the flu is monitored. “However, this is a public health concern for Hong Kong,” another source said. The city’s leader, Chief Executive Carrie Lam Cheng Yuet-ngor, last month floated a plan to shorten the time fully vaccinated people with antibodies who also test negative for the virus must spend in quarantine. Scientists, however, still cannot conclusively agree on whether the presence of antibodies gives a person immunity to Covid-19. Singapore also has different views on the efficacy of the Chinese-made Sinovac vaccine, one of two available in Hong Kong along with German firm BioNTech’s jab. In Singapore, the government offered free jabs made by Pfizer-BioNTech and American firm Moderna, while residents can pay for Sinovac shots in the private sector. Hong Kong leader hopeful over talks on reopening mainland China border The city state has pointed to a lack of data on the performance of the Sinovac jab, which is why it has yet to grant approval for the vaccine, with authorities excluding residents who took the Chinese shots in its inoculation tally. However, it was not expected to apply any restrictions on travellers who had taken that jab, according to another source. Currently in Singapore, those who receive Sinovac jabs do not enjoy perks, such as being excluded from pre-event testing, that are extended to people who took either the Pfizer-BioNTech or Moderna shots. Noting Singapore had categorically not recognised the Sinovac vaccine, infectious diseases expert Leong Hoe Nam said it would seem “counter-intuitive” to allow Hongkongers who had taken the Chinese shots into the city. “The lack of uniform treatment will just make a mockery of the travel corridor,” he said. The differentiated treatment could also affect the success of the travel corridor, he added. Singapore’s vaccination rate is higher than Hong Kong’s. Some 41.5 per cent of the 5.7 million population had been vaccinated as of Monday. In comparison, 24.7 per cent of Hong Kong’s 7.5 million residents had received their second jab as of Tuesday. One of the sources said putting in place extra measures such as requiring Singaporeans to be fully vaccinated and finding out antibody levels would serve as extra safeguards on top of previous ones. Previous arrangements included requiring travellers in either direction to undergo screening before and after arrival, to travel on designated flights, imposing a quota on travellers, and a mechanism to suspend the travel bubble in relation to untraceable infections. A spokeswoman for Hong Kong’s Commerce and Economic Development Bureau said the two governments were maintaining communications and reviewing the epidemic situation in both cities. “An announcement will be made in due course if there are further arrangements,” she said.