(Johannesburg) The risk of catching COVID-19 again is increased with the Omicron variant, according to a study by South African scientists, providing a first indication that this variant is more capable of bypassing the immunity acquired by an infection than the previous variants.
This work is based on the analysis of 35,670 re-infections identified in nearly 2.8 million individuals who tested positive in South Africa.
Between the 1er and on November 27, the risk of reinfection observed was three times higher compared to the waves linked to the Beta and Delta variants.
“The Omicron variant is associated with a substantial ability to evade immunity from prior infection,” concludes the study, made available Thursday on the medRxiv pre-publication site, but which has not yet been verified. by peers.
“We do not have information on the vaccination status of individuals in our data, and therefore we cannot draw any conclusions about Omicron’s ability to evade vaccine-induced immunity,” however warned on Twitter Juliet Pulliam of Stellenbosch University in South Africa and lead author of the study.
Last week, South Africa announced that it had detected this new variant, creating a phenomenon of global panic.
Since it has many mutations, scientists have since sought to understand whether it is more contagious or able to resist the immunity acquired thanks to vaccines or to a previous infection.
Laboratory results are still awaited, and this study therefore provides valuable first information.
It has been hailed as “high quality” by many outside scientists.
“This analysis is indeed worrying, the immunity of previous infections being relatively easily bypassed,” said Michael Head, of the University of Southampton. “Is all this just a false alarm?” This seems to be less and less the case. ”
Less severe symptoms
“We believe that a previous infection does not protect against Omicron,” Anne von Gottberg, an infectious disease specialist at the South African National Institute of Communicable Diseases (NICD), had earlier said.
According to the first observations, people re-contaminated with this variant often presented less serious symptoms, said the scientist.
Vaccines should remain effective against severe forms of the disease, she said. But the majority of experts remain largely cautious on the subject for the moment.
The variant, present to date in at least 22 countries according to the WHO, has been detected in four African countries: Ghana, Nigeria, Botswana and South Africa.
The number of official COVID-19 cases has increased by 54% on the continent in the last seven days compared to previous days, due to the exponential rise in contaminations in South Africa.
Two weeks ago, that country was reporting some 300 cases per day. It reported 8,561 new cases on Wednesday, up from 4,373 the day before.