Omicron: What we Know so Far


The first real data is emerging about the new variant, which has quickly spread worldwide. In a nutshell, here’s what it looks like as of today, grouped into the big three questions: transmissibility, severity, and ability to override immunity (vaccinated or natural) to earlier variants.

  1. Transmissibility: Omicron appears to be significantly more transmissible than Delta–2 to 3 times more, which is a huge jump if confirmed. Delta itself was transmissible enough to take over the globe from earlier variants in just a few months. Omicron could do likewise: it has demonstrated this talent both in less-vaccinated South Africa and in the antibody-soaked United Kingdom, many other countries and US states. Few epidemiologists would bet against it sweeping around the world and consigning Delta to the dustbin of COVID history just months after its own rampage.
  2. Severity is harder to pin down so far. Early evidence from South Africa shows hospitalizations lagging infections by significantly more than was the case with Delta, but South Africa also has a lot more natural and vaccinated immunity in its population than it did when Delta arrived. This greater immunity doesn’t seem to be slowing infection (Omicron has taken off even faster than Delta did there), but could be limiting severity. In other words, even if Omicron is exactly as severe as Delta, it’s attacking a better-defended population, so the impact on healthcare systems (and eventual death rate) has been milder so far. One epidemiologist compared Omicron in South Africa to Delta in India when it first exploded among an almost entirely vulnerable population, and observed that Omicron is not flooding the hospitals with sick people nearly as fast as that Delta wave. It will be very good news if Omicron turns out to be, in absolute terms, less likely to cause severe illness and death than Delta, but that’s not knowable yet. It will take time to pick apart the innate severity and the muting effects of existing immunity. Stay tuned.
  3. Immunity: Omicron does seem capable of substantially more breakthrough infections than Delta against both natural immunity and vaccine-induced immunity. Specifically, antibodies (our first line of defense), are much less aggressive against it than against all previous variants. You’ll see numbers such as “40 times less effective,” which is enough to curl your hair, but remember that this refers just to antibody response. This ability to slip past more antibodies means that Omicron is likely to cause infections in vaccinated people at a higher–possibly much higher–rate than Delta has been doing. However, our second lines of defense, T Cells and B Cells, are capable of dealing with variants better than antibodies do, even though it takes a little longer. We many see a soaring case rate among vaccinated people as the antibodies get steamrolled, but less (perhaps much less) of an increase in hospitalizations and deaths among vaccinated people, as T- and B-Cell systems blunt severity. That said, there hasn’t been time yet to determine how well B and T actually perform against the new variant. Omicron’s potential severity against entirely unprotected people is still unknown. If Omicron turns out to be more transmissive but innately LESS severe than Delta, it could actually save lives, by infecting people with Omicron before Delta can get to them. This is very speculative at this point. It doesn’t mean the total death count would be lower in the long run, since Omicron may be infectious enough to reach more people than Delta would have reached before vaccines can reach them. There’s also absolutely zero data about Omicron’s ability to cause Long COVID. It may well be about the same as the other variants, in which case an Omicron wave is going to cause a lot more Long COVID.

The most significant positive news this week is that the booster dose does seem (in the lab) to really improve protection against Omicron. Expect “fully vaccinated” to soon mean “all three” shots rather than “both” shots. 3 will be the new 2. In another bit of positive news BioNTech, creator of the Pfizer vaccine, has reminded the world that it can swiftly create an Omicron-optimized booster if needed. That’s the beauty of mRNA vaccine technology: adaptive speed.

What does this mean, and what should we do?

Omicron is now considered likely to drive a major new COVID wave over the next few months across the Northern Hemisphere. Case rates will probably break all records, and hospitalizations and deaths will inevitably rise again, hopefully at a lower rate relative to cases in previous waves. Europe, with its higher vaccination rates, will probably suffer less than the US. We will pay a high price, again, for the sheer number of unvaccinated Americans, who will not only get sick and die at higher rates, but also increase the rate of infections among the vaccinated population by increasing their exposure. Omicron could bring a major new wave of misery everywhere where vaccination rates are still low, including most of Africa.

If you have not already been boosted, pursue it now. If your kids are still not fully vaccinated, make it a priority. Although there are short-term delays in some cases, the vaccine supply chain is robust now, and there won’t be long delays or enduring shortages. Nor will you be depriving someone in the unvaccinated world of a dose–the issues have shifted away from lack of supply to lack of acceptance and lack of infrastructure. So get your booster in good conscience. Also, I hate to say, stick with the non-pharmaceutical precautions that we’re all so weary of: wear a GOOD mask indoors (not just fabric), avoid extended exposure to confined crowds, and don’t invite your antivax Uncle Fred to Christmas. That guy is a walking time bomb.

Tom Corddry
Tom Corddry
Tom is a writer and aspiring flâneur who today provides creative services to mostly technology-centered clients. He led the Encarta team at Microsoft and, long ago, put KZAM radio on the air.


  1. So much unknown still but it is a big help to read about what is known. Thank you for the concise summation – and the sage advice about all the Uncles Freds .

  2. One thing I’m somewhat hopeful about:

    In past pandemics, viruses do seem to get more virulent yet less severe as they near the end of their most damaging waves. From a Darwinian perspective, this makes intuitive sense, because a virus which kills its host does not spread, yet one which spares its host and is (from its standpoint) more infectious dominates.

    Soon, I hope, we will shift our societal measure on non-pharma-interventions from cases to hospitalizations and mortality. There are more kinds of harm than COVID, and particularly for kids and learning, we need to return to normalcy sooner rather than later. The New York Times reported yesterday that suicide attempts by American adolescent girls is up 52% from 2019, and I’m getting weary of seeing photos of children being forced to eat outside, two meters apart, on concrete in 40 degree weather.

    The most recent news from Europe is that omicron still has yet to claim its first life. That’s fantastic, encouraging news. Of course, we are also right to be cautious. But a planet can — and should — hope. Like a Seahawks fan of yesteryear with the team down by 14 heading into the fourth quarter, don’t count us out just yet.


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