What we now know about the Omicron variant

Am I protected against the Omicron variant with my COVID-19 vaccines? Is this new variant more transmissible? Will Omicron make me more sick?

With the projected number of Omicron cases expected to grow in the coming weeks, these are perhaps some of the many questions weighing on the minds of Americans as holiday get-togethers draw near.

Yahoo News Medical Contributor Dr. Lucy McBride explains what we currently know about the Omicron variant and what she advises for holiday gatherings.

(Some responses have been edited for clarity.)

Yahoo News: How effective are the COVID-19 vaccines against Omicron?

Dr. Lucy McBride: So far, we know the most about vaccine effectiveness in the face of Omicron for the Pfizer vaccine. ... We have learned through a large real-world study from South Africa that two doses of the Pfizer vaccine provides 70 percent effectiveness against hospitalization compared to people who are unvaccinated. ... But remember, Pfizer and Moderna are very similar in their mechanism of action [they both use mRNA technology], so we can assume that the Moderna vaccine will be as effective against severe disease. We don’t yet have enough information about J&J [Johnson & Johnson], but it’s probably going to be less effective against Omicron because we see that the AstraZeneca shot, which is similar in mechanism to J&J [a viral vector vaccine], also has reduced effectiveness. That said, the effectiveness of the vaccine against Omicron can readily be increased with a booster shot. [On Thursday, U.S. health advisers to the Centers for Disease Control and Prevention made changes to their recommendations, to indicate that shots manufactured by Pfizer/BioNTech and Moderna are preferred over Johnson & Johnson’s vaccine for those 18 and older, due to the possibility that the Johnson & Johnson vaccine can sometimes lead to a rare blood-clotting syndrome.]

Is one kind of booster shot better than another?

I'm recommending that all of my patients 18 and above get a single booster shot of an mRNA, either a Pfizer or Moderna vaccine, to top off their antibody levels and to help remind their memory B- and T-cells to be ready for action should they be exposed to Omicron. ... The data are clear that a booster shot helps protect us against severe disease and death and also against infection, but it's not clear whether or not it makes any difference whether we get Moderna or Pfizer as our booster. And there may be some advantage to what we call heterologous mixing [receiving a different brand of booster from the original two-dose vaccine series], but I think at this point, just get the first one you can get.

How transmissible is Omicron compared to Delta?

It's pretty clear at this point, particularly with the real world data coming out of South Africa this week, that Omicron is more transmissible, more contagious than Delta. So we can expect to see a rise in cases in the United States like we have seen in Europe and in South Africa.

How sick could a person get if infected with Omicron?

Based on the real-world data coming out of South Africa this week, it looks like people who are infected with Omicron are at 29 percent reduced risk of hospitalization compared to people who are infected with Delta. So that’s a good thing. ... It’s very promising that given the number of cases we are seeing right now around the globe, that we’re not seeing a lot of deaths being reported. That said, it’s still early and it takes a while for people who have been affected to get sick and to get severely sick. So we need to keep a close eye on this information with time.

What should Americans be advised to do for holiday gatherings?

I think we need to remember as we approach the holiday season that once you have been vaccinated, and boosted if eligible, that you’ve taken the very best step towards protecting yourself, your family, and your community. That said, you can take other precautions like masking in indoor spaces, taking a rapid antigen test before gathering with other people. But I do think we have to start to become comfortable, not that we want to be, with ongoing risk, because the coronavirus is going to be an endemic virus. It is going to be woven into the fabric of our everyday lives. And again, once we’ve been vaccinated, we’ve done the very best thing we can to protect ourselves and those around us.