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The new mutation has sparked concern around the globe, but reports from SA, where it was discovered, suggest so far that cases appear to be milder than during earlier surges. Picture: BLOOMBERG
The new mutation has sparked concern around the globe, but reports from SA, where it was discovered, suggest so far that cases appear to be milder than during earlier surges. Picture: BLOOMBERG

The Omicron variant dents the protection afforded by two doses of Pfizer’s and AstraZeneca’s Covid-19 vaccines, researchers have found, increasing the risk of infection. 

Blood samples collected from people vaccinated with the two different shots and tested against the new strain showed a substantial drop in neutralising antibodies, a proxy for protection, particularly compared with the Delta variant, researchers from the University of Oxford said on Monday in a paper.

The results echo other recent findings that emphasise the need for booster shots, especially amid evidence of Omicron’s ability to drive a tidal wave of infections.

The scientists couldn’t yet answer another key question, about the vaccines’ ability to ward off severe disease. The new mutation has sparked concern around the globe, but reports from SA, where it was discovered, suggest so far that cases appear to be milder than during earlier surges. 

Omicron’s impact should become better documented in a few more weeks, making clear whether new vaccines are needed, according to Teresa Lambe, one of the creators of the shot that AstraZeneca developed with Oxford.

“We’re hopeful that the current vaccine will protect against severe disease and hospitalisation and that’s certainly what we’ve seen before with other variants of concern,” Lambe told reporters. “We and other vaccine manufacturers are in a position that if a new variant vaccine is needed, we can go fast.”

King's College Prof Tim Spector on the latest Omicron data in the UK.

In the meantime, the rise in infections alone could strain hospitals in places like the UK. Gavin Screaton, head of Oxford’s medical sciences division and lead author of the paper, called for caution because “greater case numbers will still place a considerable burden on healthcare systems”.

The researchers saw a roughly 30-fold drop in neutralising antibodies against Omicron after two doses of the Pfizer vaccine compared with the Delta strain. The impact on the Astra shot was similar. The authors also found evidence of some participants failing to neutralise the virus at all.

Neutralising antibodies are part of the immune system’s defences, and the scientists are now looking at how T cells respond to the variant, with data expected in the coming weeks. 

The blood samples were taken from the Oxford-led Com-COV2 study looking at how mixing and matching vaccines with different intervals affects the immune response to Covid-19. The findings on Omicron were mainly based on volunteers who had two shots of the same vaccine, the researchers said at a media briefing on Monday.

The data was published on the preprint server medRxiv and has been submitted for peer review.

Bloomberg News. For more articles like this please visit Bloomberg.com.

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