Among the new cases was a 24-year-old woman who, according to the Centre for Health Protection, had been vaccinated twice. A 37-year-old man who also contracted the disease could not tell health officials if he had received the injections in the past.

The centre said the woman had travelled to Shenzhen during the incubation period, while the man had no relevant travel history. Both are listed as being in a stable condition.

On Sunday, authorities said they would tighten the rules to prioritise who among the 70,000 people working at the airport would be vaccinated, after blood tests found almost 90 per cent of the staff had previously been immunised.

Only airport workers who were born in or after 1967, had not previously received two doses of vaccination or had the disease would be vaccinated. Also, they must be living with someone who is pregnant, or have children under the age of one.

Those who have laboratory evidence of testing negative for the measles antibody are also eligible.

The daily quota of the vaccination has been reduced to 500 doses from about 1,300 doses, while 100 slots have been set aside to conduct blood tests.

But on Monday, 144 out of 360 doses prepared for vaccination slots in the morning and afternoon had been used, while only 15 blood samples were taken, according to the centre.

Li Wing-foo, vice-chairman of the Staffs and Workers Union of Hong Kong Civil Airlines, said the unused vaccines were a waste that could have been used for those in need, and he expected fewer people would be vaccinated on Monday evening.

Pregnant Cathay staff threaten to take sick leave after 33rd measles case

He cited the case of an airline employee who had been in direct contact with an infected pilot in March, when the pilot was already sick.

According to Li, the male employee had previously only had one dose of a vaccine, but he was rejected for a vaccination or any blood test on Monday after coming back from a holiday. Li said he got about 10 complaints from staff who claimed to have had only one dose.

“I think the arrangement should be more flexible,” he said. “Cases like his should be considered if there are still available doses.”

Daniel Ho, a 45-year-old airport hotel worker, and the father of a two-year-old child, was also among those rejected. He could not remember if he had been vaccinated before.

“This is ridiculous,” Ho said. “How many workers have a pregnant wife or a child under one? I bet more than 90 per cent are not eligible.

“I would not be worried if I were single. My wife and I are really concerned about affecting our child,” Ho said, noting that his wife could not get vaccinated either because of a shortage of the drug in private clinics.

Candy Yeung, a flight attendant, went to the station for a vaccination because the level of antibodies in her system was relatively low, according to her last health check.

“I thought they would let me get vaccinated if they saw that my antibody level was low,” she said. “But they would not do that, or do any check unless I had the laboratory testing report showing that I was negative for the antibody.”

Six out of 100 Hong Kong airport workers in danger of catching measles

Yeung said that even if she did the laboratory test now, it would take around a week to get the results. “I would not make it for this time,” she said.

Another four airport workers who failed to get jabs expressed concern, and said they did not remember if they had been vaccinated in the past. All their jobs required them to be exposed to a lot of people every day.

“I don’t mind them taking blood tests. But they would not do that because I didn’t fit all the requirements,” Ming Lee, an airport cleaner, said.

However, 44-year-old Alex Mora, a pilot at Hong Kong Express, was happy to finally get a jab after three days of trying. His wife is pregnant, and their son is 1½.

Mora was frustrated by the amount of time it took to get vaccinated, and questioned why most of the available injections had been given to younger members of staff.

“I understand that people are scared,” he said. “But many [who were vaccinated] are young people who already had two shots. They are well protected.”

A spokesman for the Hospital Authority said 364 staff members had been vaccinated on Monday, the first day the authority had offered jabs to frontline staff.

In the first phase, vaccinations are provided to those working in high-risk departments, such as paediatric, obstetrics and gynaecology, intensive care units and isolation wards.