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  • Writer's pictureWilliam Miller, MD

Omicron Update

We are now just over a month since the new variant, Omicron, was identified in southern Africa. Since then, it has rapidly become the dominant variant in much of the world. It is still too early to answer all the important questions regarding Omicron and how it will affect the pandemic. Yet, at the same time, government and public health leaders need to make decisions now. Waiting until all of the questions have been answered may be too late. Thus, I thought it might be helpful to review what seems to be emerging from the research thus far.

Omicron is much more easily spread than Delta, which was more easily spread than the other previous variants. The efficiency of the virus to gain access to our cells and start replicating has improved. The impact of this is that it is spreading more rapidly through populations around the globe. For those who like numbers, remember that we describe the rate of transmission as the average number of new infections that occur for each individual that gets infected. With the original Alpha variant, the rate was 2.4 meaning that a person with Alpha will infect 2.4 more people during the ten days or so that they are contagious. Each of these people will in turn then infect 2.4 more for a total of 4.8 new infections and so on. Delta was 75% more efficient with a rate of about 4.0. Omicron appears to be somewhere around 3 times (300%) more efficient than Delta which would put its rate at an impressive 12.

Fortunately, physical barriers such as masks and distancing remain as effective as before. The next question is, how effective is our immunity from either vaccination or prior infection at staving off Omicron? Previous vaccination with both shots of the Pfizer appears to be about 33% effective at preventing infection, but remains 70% effective against serious illness, hospitalization and death. Pfizer was 88% effective against Delta in preventing serious illness, so slightly less effective than before. Adding a booster shot brings that figure up to about 80%. Data on Moderna is still coming, but it is likely to be at least equivalent to Pfizer and perhaps slightly better. Keep in mind that this information is still somewhat preliminary. Interestingly, a previous COVID infection without vaccination appears to offer less protection than vaccination, perhaps as low as 20% in preventing infection. On the other hand, combining previous COVID infection and vaccination is being referred to by some researchers as giving “super immunity”. I would hold off for now on making that statement until more evidence is available.

The initial reports from South Africa suggested that perhaps the illness caused by Omicron might be less severe. However, two preliminary studies, one in the UK and another in Germany, suggested that there is no difference in severity between Delta and Omicron. Even if Omicron turns out to be somewhat less virulent, the fact that it is spreading so quickly still makes it a potential threat to healthcare systems around the world which could become overwhelmed if caseloads rise dramatically. We need to wait for larger studies to be completed to know the answer to this question. In the meantime, governments need to prepare for the worst and take necessary steps to curb spread as much as possible. There is one large study being run right now in the EU that is expected to come out in mid-January that may help give more information.

One way that Omicron may be more virulent compared to before is in younger adults between ages 18 and 30. With previous variants, that group may have felt some sense of invulnerability because the rate of serious infection, hospitalization and death was low by comparison to older groups. Some early data with Omicron suggests that in this younger age group the rates of serious infection may be higher than previously experienced. The EU study I mentioned above may help tease this out more.

A common question that I get asked is, “Are the current tests effective at detecting Omicron?” With respect to PCR tests, which are done in medical labs, the answer is that without question they are just as good at detecting Omicron as any other variant. So called “fast tests” or “home tests” that use antigen technology are probably equally effective at detecting this new variant as before, but the data is a little less certain. If you are thinking about getting any COVID test, keep in mind that neither PCR nor antigen tests are reliable until at least four days after a known exposure. So, getting tested the very next day after thinking you got exposed is pretty much useless. The recommendation is to test between day 5 and 7 after exposure and to quarantine in the meantime.

In summary, we still need more experience with Omicron to get definitive answers to these important questions. Yet, in the meantime, it seems wise to take all of the usual precautions that we already know work such as avoiding crowds, especially indoors, and wearing a good quality mask. If you have questions about the difference between types of masks you can check out my previous Miller Reports in which I addressed the topic by visiting And please, get fully vaccinated and boosted if you haven’t done that already.

Lastly, my advice is to not let Omicron hang like a dark cloud over the holidays. Of course, we need to remain mindful and stay safe, but becoming obsessed with worry isn’t helpful or necessary either. Continue to minimize your potential exposures while you celebrate the season.

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