Reports of "pox parties" being held by some parents keen to build their children's immunity to the virus have been slammed by the medical fraternity.
Dr McLean said such gatherings were tempting fate.
"You don't know if your child is going to be the one that becomes extremely unwell and has a secondary infection."
Rochelle Gribble, editor of parent advice website kiwifamilies.co.nz, said immunising against chickenpox was still a contentious issue for some parents.
While two vaccine types were available in New Zealand, Varivax - the alternative to Varilrix - was not recommended for babies under 12 months.
The vaccines, which costs parents between $50 and $100, are not part of the national immunisation schedule.
Ms Gribble confirmed some parents were sending healthy kids to pox parties, where they could be exposed to chickenpox by a sick child. Children infected with the virus were less likely to get it later in life when it could be more harmful.
The Immunisation Advisory Centre said cases of the virus normally peaked at the beginning of winter.
"It's a contagious disease and kids are spending more time indoors, mixing with each other and coughing and spluttering," centre medical adviser and paediatrician Dr Marguerite Dalton said.
A shortage of the Varilrix vaccine was a good sign, she said.
"We've finally got the message through to people that there is a vaccine and it's really effective."
Side effects from vaccination were relatively minor, compared with ailments of the disease, Dr Dalton said.
Secondary ear and chest infections and infected sores were also a risk.
Public funding towards chickenpox and rotavirus vaccinations are due to be reviewed by Pharmac this month.
APNZ
Chickenpox
Small itchy blisters on the skin.
Symptoms: tiredness, fever, aches and pains.
Usually clears up within 3-7 days.
Rare but serious complications include pneumonia and problems with kidneys, heart, joints and nervous system.
Serious for pregnant women.
Source: Ministry of Health
