Reinfections appear more common with Omicron, South African scientists say.

A previous coronavirus infection seems to offer little to no protection against the recently discovered Omicron variant, scientists in South Africa said on Thursday.

The conclusion is based on an estimate of how many people were infected before the variant came along, although emerging data support the scientists’ view.

The scientists cautioned that much about the variant remains unknown, but as Omicron drives a surge of new cases in South Africa, they are gaining more insight into it.

In an online briefing held by the World Health Organization’s regional office for Africa, government scientists said that Omicron shares some characteristics with the Delta variant that could make it more easily transmissible. Scientists now fear that the new variant’s threat lies in how susceptible populations will be to it.

Scientists have estimated that as many as 24 million people of the 60 million people in South Africa were previously infected with the coronavirus, and 36 percent have been vaccinated. Despite that, the data show many people are still getting sick, suggesting to the scientists that some people are being reinfected.

“We believe that previous infection does not provide them protection from infection due to Omicron,” said Anne von Gottberg, a microbiologist at South Africa’s National Institute for Communicable Diseases.

Previous infection offered a degree of protection against the Beta and Delta variants but reinfection has increased since the detection of the Omicron variant, said Ms. Von Gottberg, speaking during a briefing held by the W.H.O.’s regional office in Africa.

While the reinfection rate is difficult to quantify at this early stage, “it looks more than what the model would predict,” she added.

Previous infections will “hopefully” provide some protection against severe disease, hospitalizations and death, Ms. Von Gottberg said of early analysis of the variant’s spread in South Africa.

South Africa recorded a total of 11,535 new cases of coronavirus in the last 24 hours, according to data published on Thursday. The government did not yet say how many of the cases were of the new variant. While hospitalizations have increased in South Africa, only 4.1 percent of intensive care unit beds are occupied by patients diagnosed with Covid-19, a W.H.O. official said.

South Africa has also seen an uptick in daily vaccinations after the announcement of the detection of the Omicron variant a week ago, though not yet at the targets set by the government.

“Vaccines have always held out to prevent severe disease and admissions into hospitals and death,” said Ms. Von Gottberg.

The W.H.O. said it will also support the critical response and support genomic sequencing efforts in southern Africa.