The risk of catching Covid-19 again increases with the Omicron variant, according to a study by South African scientists. On the other hand, it presents less serious symptoms for recontaminated people.
Between November 1 and November 27, the risk of reinfection observed was three times higher compared to the waves linked to the Beta and Delta variants, presents the study, based on the analysis of 35,670 reinfections identified in nearly 2.8 million people. ‘individuals who have tested positive in South Africa.
“The Omicron variant is associated with a substantial ability to evade immunity from prior infection,” the investigation concludes.
Made available Thursday on the medRxiv pre-publication siteHowever, this has not yet been peer-reviewed.
No conclusion on the immunity of the vaccinated
“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,” further added Twitter alerted Juliet Pulliam, of South African Stellenbosch University, and lead author of the study.
Since the Omicron variant exhibits many mutations, scientists have sought since its discovery 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 already 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. “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, said earlier.
Symptoms less serious a priori
According to the first observations, the people recontaminated by this variant however often presented less serious symptoms, specified the scientist. Vaccines should remain effective against severe forms of the disease. 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, including France, 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. Authorities reported 8,561 new cases on Wednesday, up from 4,373 the day before.