Covid vaccines expected to protect against hospitalisation caused by Omicron, says top expert

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  • Scientists are currently studying the new variant of concern, Omicron.
  • The variant has been detected in 11 other countries.
  • Based on existing data, scientists expect the current vaccines to remain protective against hospitalisation caused by Omicron.

The emergence of new Covid-19 variants over the last several months have raised questions about when the pandemic will end. 

After the discovery of a new variant of concern (VoC) in South Africa last week, there are questions around whether the current vaccines will remain protective against the disease.

The variant, named Omicron, has already been detected in 11 other countries, as of 28 November.

"Our public health interventions all work, [but] the area that has created the concern and this global overreaction is that we're not sure about whether the current vaccines will protect against this new variant," said epidemiologist Professor Salim Abdool Karim during a media briefing on Monday.

Based on what scientists know about the other four VoCs – Alpha, Beta, Gamma and Delta – and how these variants have reacted to vaccine immunity, Abdool Karim said experts expect the vaccines will continue to offer strong protection against severe disease caused by Omicron.

Antibodies, T cells

"Protection of the vaccines is likely to remain strong. I don't know this definitively – the studies are being done – but based on what we know, we can expect that … the vaccines should hold well in preventing hospitalisation and severe disease," said Abdool Karim.

This is because the prevention of severe disease depends more on one arm of the immune system, known as T-cell immunity, and less on antibodies, another arm of the immune system.

"So even if there's some escape from antibodies, it's very hard to escape T-cell immunity," he said.

Global data on the vaccines also suggest that, even over time, the protection offered by the vaccines against severe disease, caused by the different variants, including Delta, remains effective, said Abdool Karim. This is the case for both the Pfizer-BioNTech and J&J vaccine. 

"They tend to do quite well in protecting against severe disease [and] that's our big concern with this disease - we don't want to end up with a situation where our hospitals are overwhelmed," he said.

Research ongoing

Abdool Karim clarified that the emergence of Omicron was not completely surprising.

"We were not caught with our pants down. We expected and prepared for a new variant and a fourth wave as far back as September," he said.

Scientists in the country are working around the clock to understand how the mutations of the new variant will affect how the virus behaves. 

Abdool Karim said that, at present, experts don't know all the characteristics of the variant, but that those answers will become available within the next few weeks. 

What they can do, however, is to extrapolate based on the mutations they have observed. 

"We can get some idea of what the likely scenarios are and we can plan and prepare, and respond, based on those likely scenarios," he said.

What scientists know about Omicron

The new variant has a range of mutations that scientists know well as they have already been noted in the other VoCs. 

"We know that a set of the mutations and deletions that occur are responsible for changing the way one particular PCR test responds and so it becomes a marker that helps us identify it," said Abdool Karim.

Omicron also has a cluster of mutations that are present in Delta and are known to enhance transmissibility, and so scientists expect this variant will be able to move through a community fast, he said. 

A higher transmissibility means that the country will see a sharp increase in cases, which is already happening. If this continues, Abdool Karim said that SA may exceed 10 000 cases per day by the end of this week. 

Hospitals in the country are expected to take strain within the next 2-3 weeks, even if Omicron is not clinically worse than Delta (anecdotal reports don’t raise red flags just yet). This will be due to the rapidity of transmission of the virus, said Abdool Karim.

There are unknowns

The variant also has mutations found in the Beta and Gamma variants that are responsible for some level of immune escape.

"So we expect that there will be some partial escape from antibodies," said Abdool Karim.

On the other hand, there are some mutations in Omicron the scientists have only slight information about, and there are mutations picked up that the scientists have no information about and how it affects the behaviour of the virus.

"And so a lot about this variant we simply don't know because this is a constellation - it's not only about the individual mutations," he said.

Still, Abdool Karim said there are certain situations that experts can reasonably expect from this particular variant and how it will impact the key elements of our response, including treatments and the vaccines.

Current treatments for Covid-19, including hospitalisation for oxygen, proning, dexamethasone, tocilizumab and other treatments, will remain effective, he said.

Public health interventions also still play a key role, even in the context of Omicron, he said. These include wearing a face mask, practicing physical distancing, ensuring good ventilation, especially in indoor spaces, and avoiding crowded spaces.

Reinfection among unvaccinated

Preliminary evidence suggests that some of the mutations seen in Omicron may escape antibodies derived through prior infection and vaccination. 

"And so we can expect ... more reinfection among those who've had previous infection and have not been vaccinated, because this variant will bypass some of that immunity," said Abdool Karim.

While the different Covid-19 vaccines may have different levels of protection, particularly against mild infection, they all remain highly effective against hospitalisation, he said.

"The vaccinated are less likely to have severe Covid," said Abdool Karim.

'A scientific success'

The fact that Omicron was picked up so early was a scientific success, said Abdool Karim, and added that scientists and officials now need to convert that scientific success into a "response success". 

"The last thing we need is panic and overreaction and certainly what we've seen is knee-jerk reactions, and it is really uncalled for," he said.

*For more Covid-19 research, science and news, click here. You can also sign up for our Daily Dose newsletter here.

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