Science indicates less severe omicron disease

Omicron symptoms, Headache, Fatigue, Runny nose, Sore throat, Sneezing

Fever, cough, anosmia less common

Headache, 65%

Fatigue, 65%

Runny nose, 65%

Sore throat, 57%

Sneezing, 55%

The Australia experiment

Record infections

Plans to reopen economy

Prime Minister Scott Morrison

We have to stop thinking about case numbers and think about serious illness,

living with the virus,

managing our own health and ensuring that we're monitoring those symptoms

and we keep our economy going

Queensland, chief health officer, Dr John Gerrard

Omicron, peak at very large numbers in late January or early February

We are expecting in the next few weeks very substantial numbers of people are going to be infected

I think we just have to assume that all of us are going to be exposed in the next few weeks

we can expect very large numbers of cases

and in the majority of cases,

the vast majority of cases,

the symptoms will be mild

So clearly the vaccine is working

Queensland premier, Annastacia Palaszczuk

What we’re doing is telling people to go and get vaccinated.

We have … given every Queenslander in this state the opportunity to get vaccinated

I’m now urging people in those Indigenous communities to ignore those social media posts and immediately go and get your vaccination

SARS-CoV-2 Omicron variant replication in human respiratory tract ex vivo

Omicron infects and multiplies 70 times faster than the Delta in human bronchus

Omicron variant replicated 10 times less in human lung tissue than the original SARS-CoV-2 virus

SARS-CoV-2 Omicron-B.1.1.529 Variant leads to less severe disease than Pango B and Delta variants strains in a mouse model of severe COVID-19

Mice infected with Delta compared to mice infected with Omicron

Less severe clinical signs (weight loss)

Lower virus loads

Less extensive inflammation in the lungs

T cell epitopes probably conserved

Clinical consequences of infection with the

Omicron variant may be less severe,

but the higher transmissibility could still place huge burden upon healthcare systems

The omicron (B.1.1.529) SARS-CoV-2 variant of concern does not readily infect Syrian hamsters

All other SARS-CoV-2 VoCs replicate efficiently in Syrian hamsters

In hamsters that had been infected with omicron, a 3 log10 lower viral RNA load was detected in the lungs

No infectious virus was detectable in the lungs

Histopathological examination, lungs from omicron-infected hamsters, no signs pneumonia.

The SARS-CoV-2 B.1.1.529 Omicron virus causes attenuated infection and disease in mice and hamsters

B.1.1.529 Omicron isolates

Immunocompetent and human ACE2 (hACE2)

Expressing mice and hamsters

Attenuated lung disease

Not as ill

Lower viral loads

SARS-CoV-2 receptor ACE2 and TMPRSS2 are primarily expressed in bronchial transient secretory cells

The hyper-transmissible SARS-CoV-2 Omicron variant exhibits significant antigenic change, vaccine escape and a switch in cell entry mechanism

Omicron, markedly decreased neutralisation in serology

In order

Three doses of vaccine

Immunity from natural infection (without vaccination)

Two doses of vaccine

Omicron, compared to Delta and Wuhan D614G

Titres of the Omicron variant in lung tissue,

were at least an order of magnitude lower at each time point compared to the other two variants

This is consistent with attenuated replication of Omicron in lower respiratory tissues as recently reported