There appears to be a “very large drop” in immunity against the new variant among those given Pfizer’s vaccine, said Alex Sigal, a professor at the Africa Health Research Institute, after his laboratory studied blood samples of 12 people vaccinated with the jab.
But – in results with promising implications for booster jabs – antibodies in samples from those who had been both double-vaccinated and naturally infected with coronavirus appeared significantly more effective against the new variant, according to the study, which has not yet been peer-reviewed.
Even if current vaccines prove less effective at preventing breakthrough infections in people who are double-vaccinated, scientists widely expect them to continue to offer significant protection against severe illness and death.
Studying the samples, the team in South Africa found a 41-fold decrease in levels of neutralising antibodies against the omicron variant compared with the first iteration of the virus. Previously, the beta variant had seen a threefold drop.
While these results showed “much more extensive escape”, the researchers wrote that “previous infection, followed by vaccination or booster is likely to increase the neutralisation level and likely confer protection from severe disease in omicron infection”.
They also found that the omicron variant appears to use the same protein as previous iterations of the virus, the ACE2 receptor, in order to bind with human cells – which is the target of current vaccines.
Prof Sigal wrote on Twitter that the results were “better than I expected of omicron”, adding: “The fact that it still needs the ACE2 receptor and that escape is incomplete means it’s a tractable problem with the tools [we’ve] got.”
He added that the data from the study was likely to be adjusted as the team continued their experiments.
Responding to Prof Sigal’s summary of the findings, Sir Jeremy Farrar, the director of the Wellcome Trust, thanked the team for their “hugely important” and “sobering” work.
And Professor Danny Altmann, an immunologist at Imperial College London, urged those eligible to get their booster dose, saying: “Most boosted people would fend this off nicely, even with the 40x drop.”
Amid wide praise for the team’s quick work in putting the study together, Catherine Moore, a consultant clinical scientist in virology at Public Health Wales, said: “Fantastic to see this out so soon. I think it shows what we expected, and it’s certainly not completely doom and gloom.”
The headline of this story was amended shortly after publication. It initially read: “Pfizer vaccine ‘may be up to 40 times less effective’ against omicron variant, early study suggests”, but that was not accurate. While the study found a 41-fold decrease in levels of neutralising antibodies against the omicron variant compared with the first iteration of the virus, that does not equate to a corresponding drop in the vaccine’s efficiency.