Head of the ministry's Preventive Medicine Department, Tran Dac Phu, said inspections found that vaccination standards were strictly followed at the places where the injections were given.
In the latest case, 17 primary students in the central Highlands province of Gia Lai were taken to hospital after showing adverse reactions to vaccinations against measles and rubella last week. They complained of vertigo, feeling sick and breathing difficulties.
Earlier, 12 students in the central province of Quang Ngai and four others in HCM City had similar reaction after getting the vaccination.
Phu said examination found that the students suffered adverse reactions in groups. In HCM City, after one student had a reaction, those around him reported similar symptoms. At the same time, more than 1,200 other vaccinated students reported no reactions.
Doctor Doan Manh Thang from Gia Lai Province health department said many of the affected students did not have breakfast. He claimed this made them sick after vaccination.
After being given a cup of water mixed with sugar, they quickly recovered, he said.
Phu said that to prevent similar incidents happening again, it was essential not to gather too many children in one place for their injections.
More than 9.5 million children have been vaccinated in the last two months. The National Expanded Programme for Immunisation aims to provide a combined measles and rubella vaccine to about 23 million children.
