Omicron Covid-19 Christmas case surge fears

NSW is on the cusp of another wave of infections sparked by Omicron, with analysts predicting numbers will double to 1000 a day before Christmas.

ANU infectious diseases physician Peter Collignon.

NSW is on the cusp of another wave of infections sparked by end-of-year parties and the emergence of the highly infectious Omicron variant, with data analysts predicting case numbers will double to 1000 a day before Christmas.

But, while epidemiologists predict Victoria and other states are likely to experience similar Omicron-related spikes, they say this will not translate to proportionate increases in hospitalisations and deaths, citing high vaccination rates, summer weather and the likelihood that the new variant is less virulent.

Victoria’s case numbers have fallen from a peak of 2297 on October 14 to remain steady at an average of about 1100 since early November, creeping up slightly in recent days to 1290 on Monday. NSW peaked at 1599 on September 11 and plateaued at a seven-day average of just above 220, before steadily trending upwards in December, from 260 on Wednesday, to 403 on Thursday, 420 Friday, 560 Saturday, 458 Sunday and 536 new infections on Monday.

ANU infectious diseases physician Peter Collignon said people need only compare Covid death rates in Victoria in 2020 with those in 2021 to be confident of the lives saved by vaccine coverage.

In 2020, 820 people died from approximately 20,000 cases, translating to a 4.1 per cent death rate. So far this year, there have been 598 deaths from almost 116,000 infections, resulting in a 0.5 per cent death rate of overwhelmingly unvaccinated people.

“If you look at the cases from NSW in the past week, the vast majority are in people who are under 40 and are therefore at much lower risk, and at much lower risk again if they’re immunised,” Professor Collignon said.

 

“Case numbers should not be our focus. We should look at hospitalisations and deaths. If you look at some of the predictions … made earlier this year, the Burnet (Institute) ones in particular, they were massively wrong.

“With Omicron, could it get worse? Yes it could. It probably spreads more. But we’re not seeing any evidence in South Africa of massive numbers of immunised people in hospital. We have to be careful not to overreact until and unless we see real world data.”

Epidemiological methodologist Adrian Esterman said NSW’s seven-day average reproductive rate had spiked to its highest level in four months, at 1.43 on Monday.

The reproductive rate – which estimates how many people an infected person passes the virus on to – had remained around 1 since case numbers began to stabilise after vaccination soared to 90 per cent.

Hospitalisations have also started to climb, with NSW recording 171 people in hospital on Monday, an increase from 151 on December 8.

Professor Esterman said the escalating case numbers pointed to the emergence of another epidemic curve likely to continue tracking upwards as people gathered for Christmas parties with friends and family.

“Higher vaccination rates stopped it from forming a peak a few months ago and the R-rate has been hovering around 1 for ages, but now there have been Christmas parties along with a further relaxation of restrictions,” he said.

University of Melbourne mathematical forecaster Chris Billington has been tracking outbreaks in Australia, and predicted NSW case numbers to surge above 1000 in nine days. “If Omicron is … causing this growth in case numbers, then these projections are an underestimation, and we could expect cases to increase, like we have seen overseas,” Dr Billington said.

Deakin University epidemiologist Catherine Bennett said a slight increase in Victoria’s hospitalisation rate – from a seven-day average of 293, with 41 in ICU on December 2, to 312 with 74 in ICU on Monday – was more likely to indicate under-reporting of cases than increasing virulence, despite relatively high testing numbers.

“We’re still seeing that more than 80 per cent of those in ICU are unvaccinated, despite less than 10 per cent of the population being unvaccinated,” Professor Bennett said. “We’d be expecting to see more fully vaccinated cases in ICU if we were seeing an increase in breakthrough infections.”

NSW Health confirmed 64 Omicron cases on Monday, following transmission at the Albion Hotel at Parramatta, Oxford Tavern in Petersham, Cult Nightclub in Potts Point and a party cruise on Sydney Harbour. It spread into regional NSW on Sunday, with an outbreak at The Argyle House nightclub in Newcastle linked to at least 84 cases.