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Delta outbreak is twice as infectious, but experts unsure if it’s more deadly
By Lucy Carroll
The state’s health system is treating 172 COVID-19 cases, Chief Health Officer Dr Kerry Chant said on Friday, but only a fraction of those are in hospital or being treated in intensive care units.
Experts say the Delta variant, the strain behind Sydney’s latest outbreak, is about twice as infectious as the original coronavirus Australians dealt with last year. But it is still not known whether it is more virulent, or if it will cause more severe disease or death.
Experts say the delta variant is about twice as infectious as the original variants Australians dealt with in 2020.Credit: Getty
Fourteen patients - about 8 per cent - are in hospital in NSW and three are in intensive care. None are ventilated.
“Most of these cases are being treated and managed in non-acute out-of-hospital care, including returned travellers in special accommodation,” said Dr Chant.
The most recent evidence from the UK shows the Delta fatality rate is about 0.3 per cent, compared to about 2 per cent for the earlier Alpha variant, said Professor Gregory Dore, an infectious diseases physician and epidemiologist at the Kirby Institute.
“People under 40 are the largest group being infected with Delta in the UK right now, partly because the majority of people over 50 are vaccinated and treatments have improved over time,” said Professor Dore. “But there is no evidence that Delta is more or less lethal than previous variants. It is just clearly more infectious.”
Associate Professor James Wood, an applied mathematician in UNSW’s School of Public Health and Community Medicine, said while it was early days for the latest NSW outbreak, good vaccine coverage in the state for people over 70 - about 66 per cent - could be one factor why cases in ICU and hospitalisations are still low.
“We are still relatively early in the outbreak and things can change because hospitalisations and deaths lag cases. Numbers could still go up in the next few weeks but it appears to be an improvement on last year,” he said, pointing to the Crossroads outbreak when there were 101 cases being treated in late July and five cases were in the ICU.
The most recent data shows 52 per cent of Australians aged over 50 and 69 per cent aged over 70 have now had one dose of a vaccine. Only 15 per cent of people over 70 are fully vaccinated.
Professor Dore said there was a case for bringing forward second shots of AstraZeneca vaccines for people over 60 where there is a community outbreak.
“It could be a way to see faster protection for people that are in more vulnerable age groups,” said Professor Dore.
“The guidance for second doses of AstraZeneca is between four to 12 weeks after the first, and evidence has shown overall protection against any illness seemed to be better if you delayed the second,” he said. “This strategy to delay second doses makes sense when there is limited community infection. But protection against severe disease is incredibly high even if you have the second dose after four or six weeks.”
There have been 226 locally acquired cases reported since 16 June in NSW, when the first case in a driver who transported international flight crew was recorded. Of these, 188 are now directly linked to the Bondi cluster.
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