First Omicron studies hint at enhanced role for boosters

Jolyon Attwooll

8/12/2021 4:44:19 PM

The first laboratory studies have emerged on Omicron and its impact on vaccination, suggesting ‘extensive but incomplete’ loss of protection – but the picture for severe disease remains unclear.

Lab workers analysing SARS-CoV-2 samples.
The researchers found there was a 41-fold reduction in neutralising antibodies produced against Omicron compared to the original virus. (Image: AAP)

The emergence of Omicron may reinforce the importance of the COVID-19 vaccine booster program, results from one of the first laboratory studies of the variant of concern suggest.
A preliminary report of a small laboratory study carried out by the Africa Health Research Institute released on Wednesday found an ‘extensive but incomplete’ loss of the immune protection offered by Pfizer.
The study, which has not yet been peer reviewed, seems to confirm early suggestions that the variant has more capacity to evade vaccine-induced immunity.
There were 12 participants in the study, all of whom had been vaccinated with Pfizer. Half of them had previously been infected with SARS-CoV-2.
The study compared how plasma from study participants performed in neutralising Omicron compared to the original strain in a live virus neutralisation assay.
The researchers found there was a 41-fold reduction in neutralising antibodies produced against Omicron compared to the original virus.
But while Omicron showed a much more extensive immune escape, the report notes it is not complete, particularly among those who have already contracted COVID-19.
‘Previous infection, followed by vaccination or booster is likely to increase the neutralisation level and likely confer protection from severe disease in Omicron infection,’ the report reads.
Professor Alex Sigal, a virologist at the Africa Health Research Institute, said the results indicate more breakthrough cases of COVID-19 among vaccinated people are likely, but that a third dose should also have an impact on protection.  
‘A good booster probably would decrease your chance of infection, especially severe infection leading to more severe disease,’ he said.
‘People who haven’t had a booster should get one, and people who have been previously infected should be vaccinated.’
He also says the results are better than he first feared, with the study suggesting the new variant uses the same technique to bind to the host cell via an angiotensin-converting enzyme 2 (ACE2) receptor.

‘This was better than I expected of Omicron. The fact that it still needs the ACE2 receptor and that escape is incomplete means it’s a tractable problem,’ Professor Sigal said.
The Chief Scientist of the World Health Organization (WHO) Dr Soumya Swaminathan said the results were expected and the true impact on vaccine efficacy is still yet to be established. 
‘This does not mean the vaccines will not work – T cell immunity [is] likely to persist,’ she tweeted. ‘Await more studies.’
The Chief Health Officer of Victoria, Professor Brett Sutton had a similar take and reiterated the importance of getting boosted when due.
A separate study, undertaken by researchers at the Karolinska University in Sweden, which used a pseudovirus rather than the live virus, has now also been published.
It broadly echoes the findings of the South African study, although it found samples showed ‘exceptionally variable’ levels of neutralising antibodies produced by Pfizer vaccination against Omicron compared to the original strain. This ranged from no loss to around a 25-fold reduction compared to the original.
Researcher Ben Murrell said the immune escape shown by Omicron made it ‘certainly worse than Delta’, but that the results are ‘not as extreme as we expected’.
The production of neutralising antibodies in vaccinated people has also dipped sharply against other variants of concern such as Beta. However, vaccination has usually remained effective in protecting against severe disease and death.
Commenting on the studies, Eric Topol, a professor of molecular medicine at The Scripps Research Institute in California, said the results underline a need for changes to vaccines.
‘The first/preliminary Omicron neutralisation data today … reinforce the need for an Omicron-specific vaccine, but even better, one that is variant-proof, pan-sarbecovirus, to finally get ahead of microbe evolution,’ he said.
Early suggestions of mildness
In the meantime, doctors and scientists in South Africa have continued to express a cautiously optimistic note about Omnicron’s virulence.
Data from the National Institute for Communicable Diseases (NICD) in South Africa show that in the country’s Gauteng province there is a significantly lower proportion of COVID-19 patients in hospital on ventilators compared to the most recent Delta wave, the Financial Times reports.
While the number of hospital admissions has surged in the area, the NICD has also reported a shorter average gap between admissions and discharges, another potential indicator of milder infections.
However, one virologist said it is still too early to draw conclusions and noted there is still the potential for the virus to overwhelm hospital capacity if it is more transmissible.
It is also not yet clear whether the less severe symptoms are the result of previous immunity or decreased virulence. As many as four in five South Africans have had the disease previously.
In Australia, the Omicron variant has now been detected in five states and territories, with cases confirmed in Victoria and Queensland on Wednesday.
The largest clusters have been in NSW, where there have been 34 cases confirmed as of Wednesday afternoon (8 December). However, NSW Health notes that nobody infected with the Omicron strain has needed hospital treatment so far.

There is no data yet publicly available on the impact of the variant on protection provided by the AstraZeneca vaccination, which has been received by the majority of the older, more clinically vulnerable population in Australia.
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