Underscoring increasing concerns about omicron, scientists in South Africa said Friday that the newest coronavirus variant appeared to spread more than twice as quickly as delta, which had been considered the most contagious version of the virus.
Omicron’s rapid spread results from a combination of contagiousness and an ability to dodge the body’s immune defenses, the researchers said. But the contribution of each factor is not yet certain.
“We’re not sure what that mixture is,” said Carl Pearson, a mathematical modeler at the London School of Hygiene and Tropical Medicine who led the analysis. “It’s possible that it might even be less transmissible than delta.”
Pearson posted the results on Twitter. The research has not yet been peer-reviewed nor published in a scientific journal.
On Thursday, researchers reported that the new variant may partly dodge immunity gained from a previous infection. It’s still unclear whether, or to what degree, omicron may evade protection conferred by the vaccines.
But some experts said they would expect the outcome to be similar.
“It’s scary that there are so many reinfections happening, which means that vaccine-induced immunity may also be impacted in similar way,” said Akiko Iwasaki, an immunologist at Yale University.
The omicron variant has appeared in nearly two dozen countries. The United States has identified at least 10 cases in six states. President Joe Biden reiterated Friday morning that his administration’s newest pandemic measures, which were announced this week, should be sufficient to blunt the spread of omicron.
The variant was first identified in South Africa on Nov. 23 and has quickly come to account for about three-quarters of new cases in that country. South Africa reported 11,535 new coronavirus cases Thursday, a 35 per cent jump from the day before, and the proportion of positive test results increased to 22.4 per cent from 16.5 per cent.
“It is actually really striking how quickly it seems to have taken over,” said Juliet Pulliam, director of an epidemiological modeling center at Stellenbosch University in South Africa, who led the earlier research on immunity.
Pulliam and her colleagues estimated that the risk of reinfection with the omicron variant is roughly 2.4 times as much as the risk seen with the original version of the coronavirus.