Some schools, meanwhile, have been consulting parents and pupils about their willingness to get vaccinated, as the government said it would send outreach teams to campuses where more than 300 people could take the jab on the same day.

Senior officials previously said schools with a vaccination rate of more than 70 per cent could be allowed to resume full-day classes, including on-campus lunch.

Through Tuesday, the city’s infection tally stood at 11,881 with 210 related fatalities.

Another dead end in mystery Covid-19 variant case? Hong Kong expert thinks so

Infectious disease specialist Dr Leung Chi-chiu said he believed the 1 per cent vaccination rate for the 12-15 age group in the first two days was “not too low”.

He said end-of-term exams for many schools had affected take-up, adding group and on-campus inoculation had not opened for pupils yet.

“If you look around the world, many places have not even or have just lowered the vaccination threshold to children. We are doing not too badly,” Leung said, citing England, where jabs for the over-18s were just announced, and Singapore, which just opened bookings for those aged between 12 and 39 last week.

Leung said he believed many in that young age group would get vaccinated eventually, either because they had to study overseas or simply wanted to holiday abroad. Safety data for young recipients in the United States expected to be published imminently would hopefully boost local confidence for inoculation, he added.

Health authorities, meanwhile, continued to investigate the origin of a 17-year-old schoolgirl’s infection with the Alpha variant, first confirmed on June 5, including looking into virus traces found on a frozen package of crocodile meat in her home.

The Centre for Food Safety (CFS) on Wednesday said it had taken 103 samples from crocodile products, comprising 41 swabs from food and 62 from packaging, at warehouses and retail outlets of the relevant vendor but all tested negative for the coronavirus. 

Based on the results, the CFS said, the sample from the packaging found at the girl’s home was “more likely to have been contaminated at the residence of the confirmed patient” and allowed the vendor to resume sales of the product, after ordering a halt the previous evening.

Experts also said they believed the girl was more likely to have contaminated the frozen food package rather than the other way round.

Professor Leo Poon Lit-man, from the University of Hong Kong (HKU) school of public health, said that while the coronavirus could survive freezing temperatures for weeks, it would be difficult to prove the package was the source of the girl’s infection.

But further tests should be conducted to determine if the virus traces found on the frozen crocodile meat pack were infectious, he said, while suggesting antibody tests be conducted on those who came into contact with the same batch of the product to confirm no one else was infected.

“Even if the virus’ genome sequencing of the patient and the food package matches, we cannot rule out that the patient contaminated the package,” Poon told a radio programme.

Dr Ho Pak-leung, a microbiologist from HKU, urged the public to stay calm and not be fooled by unfounded rumours circulating on social media, where some had called for people to avoid buying frozen crocodile meat from the same vendor.

Chinese University’s Professor David Hui Shu-cheong, a respiratory medicine expert and government pandemic adviser, said it was very likely the girl’s source of infection could not be traced given it had been more than a week since the case was first discovered.