The Southern District Health Board is dealing with chickenpox outbreaks at several schools across the region.
Just how many children are infected by the outbreak is not known, as the illness, though unpleasant and potentially serious, is not notifiable.
District medical officer of health Dr Naomi Gough said public health nurses reported several schools were affected in Otago and Southland, though the numbers were consistent with previous years.
A vaccine will be given to children from July 1, but it comes too late for several Dunedin parents.
Nicky Bisley said her three daughters all had the chickenpox.
Seven-year-old Molly had it about three weeks ago, and now Phoebe, 5, and Flossie, 2, were affected, she said.
Flossie was visiting the GP every day as her chickenpox was nasty, Bisley said.
"The doctor said she had a severe case.
"My children have had all the scheduled vaccinations, and because it wasn't included in those, they had not been vaccinated against chickenpox.
"Three weeks ago, my husband and I had to take a week off work between us and now we had to do this again."
Belinda Middlemass' 5-year-old daughter also had chickenpox.
Middlemass said she was surprised chickenpox was not on the notifiable list as the data should be useful in tracking how effective the vaccine was.
Dunedin North Medical Centre practice nurse Theresa Hurring said she supported the move to free varicella vaccinations for her community.
"We see some children become really unwell with chickenpox.
"Unfortunately, there's quite an outbreak here at the moment, and because of the low levels of protection in the community, it circulates quite easily.
"We've had quite a few parents choosing to pay for the vaccination for their children, but many can't afford the cost so the move to a free vaccination for young children will be wonderful for those families."
From July 1, the varicella vaccination will be free for infants born after April 1, 2016, at their 15-month immunisation visit. Older children who had not had chickenpox or received the vaccine will be able to get the free vaccination when they turn 11.
• Contagious virus spread through the air by sneezing or coughing, or touching blisters then others.
• Symptoms are small itchy blisters (like a rash) on skin, tiredness, fever, general aches and pains.
• Children are usually ill for five to 10 days.
• Use calamine lotion to treat, and take a lukewarm bath every 3-4 hours during first few days. Stay at home.
• About 50,000 people contract chickenpox in New Zealand every year.