Children with Covid-19 do not tend to become as unwell as adults, say Dr Ashley Bloomfield (file photo).

Children and teenagers tend to have low coronavirus infection rates, and don't tend to pass it on to adults, the Director-General of Health says.

Dr Ashley Bloomfield's comment comes as the country prepares to move into alert level 3 on April 27, with schools able to open two days later.

However, some in the education sector say schools and childcare centres should remain closed due to the risk of children spreading Covid-19 and causing cluster outbreaks.

However, Bloomfield said evidence from New Zealand and overseas showed Covid-19 "doesn't infect or affect children and teens in the same way it does adults".

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"Children and teens tend to have low infection rates and they don't become as unwell if they do get infected, and they don't tend to pass the virus on to adults," he said at the Prime Minister's Monday briefing.

GETTY IMAGES Dr Ashley Bloomfield says evidence shows children are at lower risk of spreading Covid-19.

Early learning centres and schools would physically be open for up to Year 10 for families that need them.

Measures would be put in place, including limiting the size of 'class bubbles', when schools open.

"We had a look at alert level three approach in the ECE or school-based environment and the advice is expressly designed to limit the potential contact that children and staff members, and therefore family, might have to someone who may be infected," Bloomfield said.

However, Peter Reynolds, chief executive of the Early Childhood Council, has called for further evidence to be provided.

"We can't find the evidence that it's safe to open," he said.

"There are several reported cases of young children contracting the disease that are hard to ignore. There's a huge amount of anxiety across the ECE community, who feel they're being forced to open their doors when it's not safe to do so."

Until he received evidence from the Ministry of Health the council would continue to call for ECE centres to remain shut until at least alert level 2, he said.

An online campaign to keep schools and early childhood centres closed at alert level 3 has also been launched.

Hamilton-based early childhood educator Hannah Swinkels​ has started the petition asking the Government to keep schools closed.

She said it was impossible for educators to keep a physical distance from their students, and with no PPE provided to them, she was terrified at the possibility of returning to work.