The Department of Health had earlier said the vaccination would begin on October 22 based on the Ministry of Health's guidelines to immunize children aged 12-17.
It even wrote to the city People's Committee saying it was preparing for the task.
Hai dismissed this, saying: "After the health ministry issues more specific instructions about what vaccines are to be used and how the vaccination would be organized, the health department would finalize its proposal. Based on that, the People’s Committee will announce plans to vaccinate children."
The health department expects to vaccinate the city's 780,000 children aged 12-17 within five days, and to decide the dates for the second shot depending on each vaccine manufacturer.
Both shots need to be of the same vaccine. Children will receive vaccination with the consent of their parents or legal guardians.
The department and ministry have said they are set to train their personnel in vaccinating children.
Ho Chi Minh City has so far administered at least one shot to around 7.1 million people, with 5.4 million being fully vaccinated.
The city plans to reopen schools in January next year.