Many children under three months of age, including a nine-day-old patient, contracted the disease from their mothers, he said.
To Minh Trang of Long An province said that she had contracted chickenpox four days before delivering her baby.
Nine days later her newborn baby developed symptoms of chickenpox with blisters on the face, hand and feet.
Newborn babies are highly vulnerable, and the mortality rate in newborns is very high at 25%-30%, Khanh said.
He advised that women of child-bearing age and children should get the chickenpox vaccine.
Nguyen Tran Nam, head of the infection ward, said the number of outpatients with chickenpox too has soared in the past few days.
The illness is usually mild but it can be dangerous for some people such as pregnant women, newborn babies and people with weakened immune systems