A recent scandal has caused widespread concern over the vaccines used on the Chinese mainland, and many parents have said they will go to the Hong Kong Special Administrative Region, where the regulations are stricter, to get their children vaccinated.

With concerns in Hong Kong that its vaccine supplies might not be enough to meet the demand for residents if there is an influx of "vaccine tourists", the health authorities in Hong Kong have announced they will limit the number of non-resident children who can get vaccinated in public hospitals and health centers to 120 a month from April 1. Non-resident children will only be able to book an appointment when there is spare capacity and will have to pay a higher fee.

"The government's policy is to accord priority to local children", said Teresa Li, Hong Kong's assistant director of Health for Family and Elderly Health Services, in a statement.

She said utilization of services by non-resident children would be closely monitored and the quota adjusted or withheld as necessary.