Variant ‘of concern but not of doom or panic’, experts say

Epidemiologists are split of the infectiousness of Covid-19’s Delta strain, although even those less concerned say it is a variant ‘of concern’.

Epidemiologists are split of the infectiousness of Covid-19’s Delta strain, although even those less concerned say it is a variant “of concern”.

As Victorian authorities consider their pathway out of lockdown, infectious disease researchers have urged caution about equating the British and Indian experience with what could unfold in Australia.

Canberra Hospital infectious diseases physician Sanjaya Senanayake said it was not yet clear that the Delta variant was more infectious than other strains in the Australian context, and while it was “a variant of concern ... it is not a variant of doom or a variant of panic”.

“Biologically it might be more transmissible but if you look at the Australian situation in terms of population density, climate and the public health response, it might not be that different from other strains,” he said. “We should be concerned but we don’t need to institute or maintain a lockdown just because it’s the Delta strain.”

The evidence so far is that the levels of infection in Victoria are similar to those of previous outbreaks with different versions of the virus, Australian National University microbiologist Peter Collignon said. “Of the 6000 close contacts, case numbers fit within the historical 1 or 2 per cent infection rate we’ve experienced before.”

The head of the Kirby Institute’s biosecurity program, Raina MacIntyre, said international evidence should be heeded when it came to the Delta strain. “It is the most infectious variant of all. It’s at least 50 per cent more transmissible than the UK variant, which is itself twice as transmissible as the strain that caused Victoria’s second wave last year,” she said.

“And vaccines might be effective against it after two doses, but are not as effective after one dose. This is a significant concern, particularly in aged care, so getting aged-care staff vaccin­ated is really important.”

Professor Collignon said there was no reason, based on current numbers, why Victoria could not ease restrictions late on Thursday. “If we don’t see unlinked cases in the community and the number of linked cases found by contact tracing is declining by Thursday, then my answer is yes (to ending the lockdown),” he said.

Catherine Bennett, chair in epidemiology at Deakin University, said the circuit-breaker lockdown in Victoria was designed to let the authorities get ahead of the virus and “they’re pretty much there”.

“Apart from new staff going into aged care, all the other cases on Monday were within the footprints of the two outbreaks,” she said.

“If we have two more days of this, I’d suspect they’d be ready to end the hard lockdown. They should make the call for Thursday night.

“I’d say we should go back to restrictions in place just before the lockdown, for instance masks and limits on indoor gatherings, but based on previous experience with the Victorian government there may be a few other limitations.”

Existing Covid-19 vaccines are able to protect against the Delta strain, UK studies show.

STEPHEN LUNN