Dec 20: What more we know about Omicron today

At present, the South African experts stress, this is not enough to make a sound conclusion of Omicron being milder.

Is the Omicron variant indeed milder?

It is too early to reliably assess the severity of disease caused by Omicron, the experts said, and “some severity estimates should start to become available in about a week as hospital data accumulate”.(Reuters)

Experts based in South Africa, where the variant was first detected in the Gauteng province, have said that they think so. Their assessment is largely based on comparisons of how fewer hospital beds have filled up at the beginning of the Omicron wave, compared with the trajectory of the Delta variant.

At present, the South African experts stress, this is not enough to make a sound conclusion of Omicron being milder. Other experts, mostly based in the UK, which has the second-largest Omicron outbreak, agree the data is inadequate for such a conclusion.

In fact, UK experts say preliminary signs indicate there may be no difference in severity at all. This assessment was part of discussions during the latest meeting of UK’s top medical experts body, the Scientific Advisory Group for Emergencies.

“Although a preliminary analysis from South Africa suggests that this wave may be less severe than previous waves, a comparison of SGTF (mainly Omicron) and SGTP (non-Omicron) cases within this wave suggests less difference between variants,” said the situation update discussed at the meeting, according to minutes published on Saturday.

It is too early to reliably assess the severity of disease caused by Omicron, the experts said, and “some severity estimates should start to become available in about a week as hospital data accumulate”. Crucially, the update added, “even if there were to be a modest reduction in severity compared to Delta, very high numbers of infections would still lead to significant pressure on hospitals”.

Also over the weekend, one of South Africa’s top experts, Tulio de Oliveira, director of Centre for Epidemic Response & innovation, urged caution on interpreting the situation in Gauteng province, which contains Johannesburg, the country’s largest city.

“The reason is that Gauteng gets quite empty and 100,000s of migrant workers and holiday makers leave,” he said in response to experts seeing signs that Gauteng’s outbreak may have peaked.

Research identifies new Omicron strength

Researchers from Ohio State University released findings that corroborate some of the lab research work that has come out of late: The Omicron variant is highly resistant but does not bind to target cells as efficiently as the Delta variant, and it does not cause cell-to-cell fusion, which creates giant cells known as syncitia. The virus’ ability to trigger syncitia formation, or fusogenicity, has been linked to more severe symptoms, such as in Delta.

But their research suggests Omicron may be more capable in “cell-to-cell transmission”. This could have several implications, they said.

“Cell-to-cell transmission is commonly used by many viruses, including Sars-CoV-2, and is a highly efficient mechanism of virus spread within a host… Enhanced cell-to-cell transmission may help compensate for other observed defects in the Omicron S protein, such as reduced ACE2 binding and fusogenicity...,” they said.

When the virus transmits primarily between cells, the researchers said, the method is resistant to neutralizing antibodies that bind to viral particles prior to their entry into cells, therefore “implicating another potential mechanism of Omicron immune evasion”.