The Omicron variant, spreading now in southern Africa and detected in over 30 other countries and regions, has prompted fears it could significantly undermine the effectiveness of vaccines against COVID-19.

Yet as scientists race to understand the full consequences of Omicron, some are also asking whether this new version of coronavirus might cause milder illness than its predecessors.

What does data show?

The collected data showed among 70 cases reported in Europe that included information on disease severity, half of the patients had no symptoms and half had mild symptoms, according to a report on Thursday by the European Center for Disease Prevention and Control.

There were no cases of severe disease, hospitalization, or death. However, the European agency said it would require data on hundreds of cases to accurately assess disease complications, estimating that could take several weeks. In addition, most cases detected in Europe so far have been in younger people who were fully vaccinated, making them less likely to suffer severe illness.

In South Africa, where the daily number of reported COVID-19 cases doubled on Wednesday to 8,561, symptoms for reinfected patients and those infected after vaccination appear to be mild.

"Some evidence from South Africa suggests that it may actually cause more mild illness but … I caution you that a lot of the patients South Africa initially were among young university students," Dr. Carlos Del Rio, an infectious diseases expert at Emory University in Atlanta, said on Thursday during an online briefing from the Infectious Diseases Society of America.

Is Omicron a 'less fit' version of coronavirus?

While data on real world infections continues to emerge, scientists are conducting laboratory studies to decipher Omicron. The variant has about 50 mutations not seen in combination before, including more than 30 mutations on the spike protein the coronavirus uses to attach to human cells. Vaccines in current use target that spike protein.

"Typically when viruses accumulate a lot of mutations they lose some fitness," said Dr. John Wherry, director of the Penn Institute for Immunology in Philadelphia. Certain Omicron mutations may impair the ability of the virus to cleave, changing the behavior of the spike protein, he said.

Can Omicron overcome immunity from vaccines or infection?

The fast rise of Omicron cases in South Africa could be due to its capability to infect people who have been vaccinated or recovered from COVID-19 caused by other variants, according to the scientific journal Nature.

Researchers around the world are still working on measuring how much the Omicron variant can evade immune response.

Previous studies showed Omicron's spike mutations suggested that the variant will blunt the potency of neutralizing antibodies, which means the variant can be resistant to the immunity triggered by the vaccines or the previous infection.

However, it doesn't mean the immune responses will serve no protection against the variant. According to Nature, the modest levels of neutralizing antibodies may protect people from severe illness caused by COVID-19.

Will Omicron become the dominant variant?

If Omicron does become dominant, but causes milder illness, it could mark a turning point toward the virus eventually becoming a seasonal threat, like influenza, said Sumit Chanda, an infectious disease researcher at the Scripps Research Department of Immunology and Microbiology in San Diego.

The European Union's public health agency said on Thursday the Omicron variant could be responsible for more than half of all COVID-19 infections in Europe within a few months.

Although it's still unclear how effective the vaccines and the booster shots will be against the variant, Paul Bieniasz, a virologist at Rockefeller University in New York City, and his team have already found some evidence showing people who are repeatedly exposed to the COVID-19 spike protein, whether through infection or a booster shot, are "quite likely to have neutralizing activity against Omicron," Bieniasz said in a September 2021 Nature paper.

While the research into Omicron is underway, disease experts say people must remain vigilant against the coronavirus by getting either initial vaccinations or booster shots, as well as wearing masks in indoor or crowded settings, ventilating rooms and washing hands.