The new omicron variant is spreading fast. But research is beginning to catch up.

Because an early case was detected in San Francisco, local scientists have quickly started growing the virus in high-security labs at UC San Francisco, UC Berkeley and Stanford.

Using cell cultures, they’ll soon learn how readily it transmits, whether it can dodge our defenses and outcompete delta. In mice, they’ll study whether it produces illness that is severe or mild.

“In one or two weeks, we will have a much clearer picture of what this variant is going to do to us,” said Dr. Melanie Ott of UC San Francisco’s Gladstone Institute of Virology and Immunology.

Meanwhile, South Africa studies have begun to offer a real-world glimpse of how much risk omicron poses.

The extent to which omicron’s sudden spread is caused by immune evasion or more contagiousness — or both — is yet unclear. But as the variant expands into 17 U.S. states and at least 45 nations worldwide, here’s what we’re learning:

Q: Is omicron more or less dangerous than delta?

A: A new small study suggests that omicron may cause less severe illness than previous variants like delta.

The best indicator of disease severity is the in-hospital death rate. A report this weekend identified 10 omicron-linked hospital deaths at two South African hospitals, representing about 6% of 166 COVID-related admissions. This compared to a 17% death rate at the hospitals among COVID-19 patients during previous waves of infections. However, this time it wasn’t just elders who died; four of the deaths were in adults ages 26 to 36.

The same hospital said that the majority of COVID patients did not need extra oxygen, and far fewer were so sick that they were admitted to the ICU. Most discovered they were infected only after being admitted to the hospital for other health reasons. The average hospital stay was only 2.8 days, down from 8.5 days during infection with other variants.

Most of these patients were unvaccinated, although there were some vaccinated admissions, as well.

Can this be generalized given the younger population in South Africa, with very extensive prior COVID? That’s an uncertainty that will remain until we see much larger numbers of infections in older people.

— South African Medical Research Council

Q: What’s the latest guess about how infectious it is?

A: In South Africa, about 3 to 3.5 new omicron infections are estimated to stem from a single case. In contrast, the reproductive rate of delta in South Africa and the U.S. was about 1.5.

If omicron’s reproductive rate continues at around 3, this indicates a much larger threat, in terms of case counts, than delta. The size of the wave depends on the susceptible population.

— Trevor Bedford, Fred Hutchinson Cancer Research Center in Seattle

Q: Will omicron overtake delta?

A: In South Africa, omicron has surpassed delta as the dominant strain. But delta was on the wane there, so omicron had an open field to run in. Omicron did not have to push delta out.

What we don’t know is how well omicron will compete in an environment that’s 99.9% delta, such as California.

— Dr. Warner Greene, Director of Gladstone Institute of Virology and Immunology, UCSF

Q: If it outcompetes delta, and it’s milder, isn’t that good news?

A: It would be great if omicron is always a mild virus. But we don’t know that yet. It will take a month or so to learn the virulence of this variant, and whether it will replace delta.

— Dr. Warner Greene

Q: Will my previous infection protect me?

A: Perhaps not. South African doctors are seeing an uptick in “reinfections” among people who tested positive for the virus at least 90 days earlier, suggesting that immunity acquired through natural infection is not fully protective.

Omicron is three times more likely to cause reinfection compared to delta, according to a Dec. 2 paper.

— Juliet Pulliam, director of the South African Centre for Epidemiological Modelling and Analysis, Stellenbosch University

Q: Are vaccines protective against infection?

A: We don’t yet know. In infected patients in one very small South African study, more than half were considered fully vaccinated, with two shots.

But it’s unclear how much time had passed since their inoculation. If it was more than six months, their antibody levels had waned.

These patients hadn’t gotten boosters. Boosting creates a huge increase in antibodies — much more than what is achieved after the second vaccine dose. That’s what is leading vaccinologists to hope that even if antibody levels start to decline, protection will last longer. It’s starting at a much higher level.

— Dr. Warner Greene

Q: How long will it take to design omicron-specific vaccines?

A: Vaccine makers Pfizer and Moderna say they can get one ready within 100 days. Making a new mRNA vaccine will involve generating a new genetic sequence, based on omicron, and encapsulating it in a fatty substance such as a lipid.

This autumn, the vaccine companies have been doing dry runs, practicing all aspects of executing a strain change — the preclinical research, the manufacturing, the clinical testing and the regulatory submissions — so they are ready to respond quickly.

— Journal Nature

Q: Then will we have to wait for new clinical trials and FDA approval?

A: The FDA told the Wall Street Journal that it is already in conversations about streamlining authorization for revamped vaccines. Agency officials have met with vaccine makers and are working to set guidelines for the type of data that will be needed to swiftly evaluate the safety and efficacy of changes to current vaccines.

— Wall Street Journal

Q:  Should omicron change how we celebrate the holidays?

A: It’s probably best to avoid international travel. It’s far better to fly domestically than take a “long haul” flight to Europe, Asia or Africa. And be careful about where you fly domestically. Don’t fly into a hot zone.