Omicron variant expected to become dominant strain in Australia as NSW records 1,360 new Covid cases

A third booster Covid-19 vaccine dose will be essential to get high protection against symptoms from the Omicron variant and it appears likely the variant will become the dominant strain in Australia, virologists from the Kirby Institute say.

The new data from the Kirby Institute comes as Covid-19 case numbers in New South Wales jumped again on Wednesday to 1,360, 25 of them are the Omicron variant. There are now 89 Omicron cases in NSW.

The researchers also said Covid boosters may be required every six months to protect against the variant.

Virologists from the Kirby Institute presented new data on Wednesday after growing the Omicron variant in a laboratory and testing how it responded to various samples, including from the fully vaccinated, from those who had recovered from the virus but were unvaccinated, and those who had recovered from the virus and also received two vaccine doses.

The data has now been sent to all chief health officers across Australia.

Despite their vaccination status, they were as infectious as unvaccinated people, Turville said.

However, he said it was likely those two travellers had a poor vaccine response and this did not mean two doses of the vaccines offered zero protection against any infection from Omicron. Data from South Africa released overnight suggested protection from infection was 33% for those who are double-dosed, similar to the Kirby data which predicts 37%.

It is too early into the booster rollout to have collected enough samples from people with three doses of the vaccine to see how Omicron behaves against it. The Kirby Institute researchers hope to have ethics approval and enough study participants to begin taking samples from those who have had three doses next week.

But the researchers said they had mimicked the impact of a booster shot against Omicron by seeing how samples from people who had the virus and therefore had natural antibodies, and then who had also received a double-dose of the vaccine, responded to the variant.

Cromer added that while it seemed this booster may offer protection for at least one or two years, it was appearing likely that ongoing boosters would be needed against Omicron, as frequently as every six months.

Turville said it appeared likely that the variant would overtake Delta, based on the way spread is accelerating overseas.

The president of the Australian Medical Association, Dr Omar Khorshid, warned that the booster program was being rolled out too slowly and that vaccination hubs needed to continue to run.

The Kirby Institute researchers said they did not want to preempt any advice about boosters. The Australian Technical Advisory Group for Immunisation (Atagi), which advises the government on vaccination, would consider the Kirby data along with data coming from other research groups, including those overseas.