Only a handful of children had long-term symptoms, he said, noting a new study of more than 1700 British children in which only 4.4 per cent had symptoms that lasted more than four weeks.
He said routine vaccination of 12 to 15-year-olds would not make an important difference to herd immunity but those with medical risk factors should be inoculated.
When we have more than 80 per cent of adults vaccinated next year, thats we can start vaccinating children, he said.
Federal Health Department data shows more young people are coming forward to get vaccinated, with the number of people in NSW under 30 who have had a first dose almost doubling in the past two weeks.
By the end of Tuesday, 12 per cent of teenagers aged 16 to 19 in NSW had received a first dose of a COVID-19 vaccine, up from about 7 per cent a week earlier. The state government on Monday started a vaccine program for thousands of HSC students from Sydneys west and south-west.
First-dose rates in people aged 20 to 24 increased from about 16 per cent to 21 and almost one-quarter of 25 to 29-year-olds have received a first dose compared to about 18 per cent a week earlier.
Data released by the American Academy of Pediatrics this week found children accounted for about 15 per cent of all new COVID-19 cases across the United States in early August. There was no clear answer on whether the Delta strain was making children sicker, it said, but severe illness remained rare.
Professor Collignon from the Australian National University in Canberra said Delta seems to be affecting kids more than previous strains. It is behaving differently, but a big factor here is immunisation with few people under 20 vaccinated and nobody under 10 is immunised, he said.
There have been 36 deaths during the Delta outbreak, including 27-year-old man Aude Alaskar and 38-year-old woman Adriana Midori Takara. A man in his 30s from Belrose died at Northern Beaches Hospital this week.
Increasing numbers of young people are being admitted to hospital. Of the 62 cases in intensive care on Thursday, three are in their 20s, seven in their 30s and five in their 40s.
Intensive care specialist Dr Stephen Warrillow, from Melbournes Austin Health, said the high proportion of cases in under 30s with the virus is a consequence of young people not having many opportunities to be vaccinated.
The Australian Technical Advisory Group on Immunisation recommended in late July anyone over 18 in Greater Sydney strongly consider getting the first available vaccine, including AstraZeneca.
Children and young people are much less likely to become critically ill than older people, Dr Warrillow said, but that is not to say children dont ever become very sick and can deteriorate quickly. Essentially, this is a virus of the unvaccinated, he said.
On Wednesday, NSW Chief Health Officer Kerry Chant asked parents to keep younger children home where possible, due to higher numbers of cases in childcare centres than in previous outbreaks.
Over the entire course of the Avalon and Berala clusters (218 cases), 50 infections were recorded in teenagers and children aged 19 and under. 120 cases were recorded in this age group among the 556 cases in the Crossroads cluster in mid-2020.
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