Spread of COVID highest in a month as Omicron cases grow

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Transmission of coronavirus in Victoria has risen to its highest level in a month as Omicron cases continue to increase, prompting infectious disease experts to call for a further shortening of the waiting time for booster shots.

Epidemiologists warn it is inevitable a significant Omicron outbreak will seed in Victoria, setting the state on a similar trajectory to NSW. There are now 13 confirmed Omicron cases in Victoria and genomic sequencing is underway for another 17 suspected cases of the variant.

The Omicron variant has spread throughout the world but there is no convincing evidence so far that it causes more serious disease than Delta.Credit:AP

As Victoria reported more than 1600 new coronavirus infections on Thursday, including three more Omicron cases, the effective reproduction number – the most reliable indicator of how the epidemic is growing – rose for the first time since November.

This key metric is used to measure how many people each infected person passes the virus on to. University of South Australia epidemiologist Adrian Esterman, who has been closely tracking Victoria’s outbreak, said the number had now increased to 1.09, indicating a sudden surge in transmission.

“It means that the rate of growth of cases is starting to go up in Victoria and this has been reflected in a big jump in cases overnight that looks set to continue to increase in the coming days,” said the former advisor to the World Health Organisation.

The three new confirmed Omicron cases were all recent international arrivals who have been in quarantine since arrival.

Concerns have been mounting that Victoria’s vaccination hubs are closing at a time when thousands of people urgently need booster shots. But late on Thursday the government confirmed it would keep the Royal Exhibition Building hub and Wyndham drive-through clinic open over Christmas.

The Royal Exhibition Building, the largest vaccination hub in the state, was due to close on Friday.

The decision to keep the hubs open came after hundreds of people were exposed to the Omicron variant at the Peel Hotel in Collingwood and at the Sircuit bar in Fitzroy on Friday night, plunging more than 700 people into isolation.

The Health Department is investigating whether seven COVID-19 cases are linked to the venues and if any are the Omicron variant.

Professor Esterman is among a growing number of experts calling on the federal government to again shorten the interval between the second dose and the booster shot from five to three months, arguing it is our “most important defence” against Omicron.

In the UK, where new cases have soared to almost 80,000 a day, authorities have cut the time between the vaccine and booster to three months. In Denmark, the interval has been reduced to four and half months.

Australian infectious disease expert Professor Paul Griffin, who has been the principal investigator for seven COVID-19 vaccine clinical trials, supported further cutting the time between doses as Omicron cases increased nationally.

“It makes sense to use boosters to our advantage and I expect the interval between doses will be brought forward again,” he said.

While Professor Esterman suggested the interval should be cut to three months like in the UK, Professor Griffin said there should be flexibility between the three and four months mark.

“If we bring forward the boosters again it’s obviously going to create a huge demand and so that that logistical support for these decisions needs to be required early,” he said.

However, leading vaccine expert at the University of Melbourne Fiona Russell did not believe it was necessary to accelerate the booster program again just yet.

Professor Russell argued Australia was in different position to the UK and Europe, which faced the “double whammy” of increased infections in winter and an earlier vaccination program which meant immunity had already waned among its adult population.

The most critical defence was ensuring boosters were being administered to those most at risk of severe disease in Australia, including the population aged over 60, most of whom were already eligible for a booster, Professor Russell said.

“They are the absolute key priority,” she said.

Melbourne University professor James McCaw, who has provided expert advice and modelling to the federal government throughout the pandemic, said even if the nightclub exposures last week did not become a super-spreading event, there was still every chance Omicron was already spreading undetected.

Professor McCaw said it was “essentially, inevitable” Victoria would follow a similar path to NSW. But ensuring everyone with even the mildest symptoms was tested while ramping up boosters for those eligible in Australia was crucial to containing the spread.

“I would expect that if it’s not this event in Fitzroy, it will be something at a nightclub next week or at a school. It will happen somewhere in Victoria in the next few days,” Professor McCaw said.

Once the outbreak is seeded, the mathematical biologist and epidemiologist forecasts the state will follow the same pattern as every other place in the world where the variant is transmitting, with cases doubling “every three to four days.“

On Thursday, new infections in New South Wales were higher than Victoria for the first time since late September, with the state recording 1742 cases. It followed the release of grim modelling by the public health unit at the University of NSW, which projected there could be 25,000 cases of the virus in NSW a day in January.

Asked whether Australia should cut its interval between the second dose and the booster shot to three months, like the UK, Professor McCaw said there were “very robust and carefully considered” high-level discussions about this happening nationally now.

He said it was widely accepted that one of the reasons the variant was spreading so quickly globally was because it could evade existing vaccines and two doses did not offer enough protection.

Preliminary data suggests Omicron is highly transmissible, but there is some indication it appears less likely to cause serious illness than the Delta variant.

The seven-day average for hospitalisations has risen for the past nine days, from 296 on December 7 to 384.

There are now 87 Victorians in intensive care and 49 are on a ventilator. Another 35 Victorians remain in ICU, but have been cleared of the virus.

Professor McCaw said before Omicron, he was not concerned hospitals would be overwhelmed by Delta, due to the booster program and immunisation of 5 to 11 year-olds. But, he said, the new variant had changed that.

“We don’t know what the consequences of Omicron will be,” he said.

“The booster program is one of the most important defences against Omicron, so we need as many people as possible to get boosted as soon as possible. This will help slow the spread of this virus and will almost certainly help reduce clinical outcomes of severe disease as well.“

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