Preliminary results from laboratory studies to ascertain how the Omicron variant of SARS-CoV-2 evades immunity have shown that the COVID-19 causing virus has a high tendency to compromise the protection offered by vaccines.
Although the results of the studies led by teams in South Africa, Germany, and Sweden, and the Pfizer-BioNtech collaboration published on Wednesday by Nature suggest that the protection conferred by existing COVID-19 vaccines won’t be totally wiped out, they have said there is likelihood of upsurge in cases of reduced effectiveness of vaccines preventing against the infection. But they have also said booster shots could improve immunity to Omicron.
“We’re likely to see reduced effectiveness of vaccines against preventing infection,” Penny Moore, a virologist at the University of Witwatersrand in Johannesburg, South Africa, who co-authored one of the studies was quoted by Nature.
The Nature, however, noted that the studies, which measure the capacity of antibodies in people’s blood to block the infection of cells in a dish, have not yet been peer reviewed, hence do not tell researchers the extent to which vaccines’ ability to protect against COVID-19, especially the most severe forms, could be compromised by Omicron.
“We still need to wait for more effectiveness data and clear signals from the places where this is blowing up first,” Ben Murrell, an interdisciplinary virologist and immunologist at the Karolinska Institute in Stockholm, who co-led one of the studies told Nature.
Omicron was identified by researchers in Botswana and South Africa in late November. Since then, teams across the world have been working to understand the variant’s properties and the risks it poses. Preliminary data from South Africa and elsewhere suggest that the variant is highly transmissible, spreading several times faster than Delta, and that it might have the capacity to infect people who are immune to other variants.
One important finding so far is that Omicron carries a large number of mutations in its spike protein, the prime target of immune responses, and that some of these changes, when present in other variants, affect the ability of antibodies to recognize the virus and block infection.
One of the studies led by virologist Alex Sigal, at the African Health Research Institute in Durban, South Africa, found that serum from 12 people who received the Pfizer-BioNtech vaccine was 40 times less potent against Omicron, on average, compared to an earlier strain of SARS-CoV-2. That was similar to two other studies, one of which was reported by Pfizer and BioNtech in the 8 December press release, and the other released on Twitter by virologist Sandra Ciesek at Goethe University in Frankfurt, Germany.
A fourth study, led by Murrell and virologist Daniel Sheward, also at the Karolinska Institute, reported a smaller reduction in levels of Omicron neutralizing antibodies in two different groups of participants: 17 healthcare workers, who had all been previously infected, and 17 Swedish blood donors. The researchers cannot determine the vaccine status of the anonymous blood donors, but say they will soon update their paper with vaccination information from the healthcare workers.
Murrell said despite differences in the labs’ results, which are common in such virus neutralisation assays, their conclusions are similar, and show that Omicron’s effects on neutralizing antibodies are not complete knockouts.