People register for COVID-19 vaccination at Soweto's Baragwanath hospital, South Africa, Monday Dec. 13, 2021. South Africa's 7-day rolling average of daily new COVID-19 cases has risen over the past two weeks from 7.60 new cases per 100,000 people on Nov. 28 to 32.71 new cases per 100,000 people on Dec. 12, according to Johns Hopkins University. In general, the new omicron cases have resulted in milder cases, with fewer hospitalizations and less severe cases requiring oxygen or intensive care. (AP Photo/Jerome Delay)

JOHANNESBURG (AP) — The omicron variant is offering more hints about what it may have in store as it spreads around the globe: A highly transmissible virus that may cause less severe disease, and one that can be slowed — but not stopped — by today’s vaccines.

An analysis Tuesday of data from South Africa, where the new variant is driving a surge in infections, suggests the Pfizer vaccine offers less defense against infection from omicron and reduced, but still good, protection from hospitalization.

The findings are preliminary and have not been peer-reviewed — the gold standard in scientific research — but they line up with other early data about omicron’s behavior, including that it seems to be more easily spread from person to person.

The spread can be seen in Britain, the United States and Denmark, where confirmed omicron cases are increasing at a worrisome pace, said Dr. Jacob Lemieux, who monitors variants for a research collaboration led by Harvard Medical School.

“Omicron is moving extraordinarily fast, faster even than the most pessimistic among us thought it was going to move,” Lemieux said.

During past waves of the pandemic, the U.S. could look to Europe and Britain for an early signal of what was coming, Lemieux said. “With omicron, it seems to be happening everywhere all at once with extremely rapid kinetics.”

It’s unclear whether omicron’s rapid spread will overwhelm hospitals. In South Africa, although case numbers are rising, hospital admissions for adults diagnosed with COVID-19 are 29% lower compared to the wave the country experienced in mid-2020, after adjusting for vaccination status, according to the new analysis.

Still, some experts cautioned that it’s too soon to draw conclusions since the variant is quite new and hospitalizations can lag weeks behind infections.

When omicron reaches broader populations more useful information will emerge, said Dr. David Dowdy, an infectious disease epidemiologist at Johns Hopkins Bloomberg School of Public Health.

“To date, omicron has disproportionately infected young adults — people who probably have more social contacts and are more likely to attend large gatherings,” Dowdy said. Young adults may be more likely to be sick without knowing it, have more intense exposures and experience milder disease, he said.

“Our society needs to learn how to wait, rather than either panicking or dismissing early findings,” Dowdy said.

U.S. health officials estimate that a small, but growing proportion of new COVID-19 infections are due to omicron, and that the rise is particularly dramatic in some places.

Two weeks ago, omicron accounted for less than 0.5% of the coronaviruses that were genetically sequenced in the U.S. That rose to about 3% last week, the Centers for Disease Control and Prevention reported Tuesday.

But it varies from place to place, and is as high as 13% in the New York/New Jersey area, according to the agency.