Last week I posed three questions about Omicron that I want to revisit.
Is Omicron more infectious?
Yes. Omicron is by far the most infectious Covid variant we’ve seen. It’s staggering to look at some of the charts of how fast it becomes dominant. Doubling time for Omicron is 2-3 days. Once Omicron accounts for more than a few percent of Covid cases, it’ll be 100% of all cases in about two weeks. That puts estimates for it to be the dominant strain in early January in the US.
Does Omicron evade immunity?
Yes. Omicron has substantial immune evasion for infection. To clarify, infection is different than a severe disease which I’ll deal with shortly.
Studies this week showed that if you have been twice vaccinated with AstraZeneca, you have basically no protection against Omicron. If you have two doses of Pfizer, you have ~30% protection [vs. 90% initially]. If you have been vaccinated twice and boosted with Pfizer, it jumps protection to 70%+. If you’ve had Covid previously, you have a 3-8x chance of being reinfected vs. Delta. Household transmission is about twice what it was with Delta.
The best studies on protection show that those who had Covid and are vaccinated are best off.
The take-home here is clear; go get your booster.
Does Omicron cause as severe disease as other variants?
Possibly not. Again it’s still extremely early in this wave, but every day that passes that we don’t see huge spikes in hospitalizations adds to the data it may be less severe. Now why it might be less severe is still an open question. It may not be something about the virus but due to widespread prior immunity in those affected.
You can think of our immune system [this is an oversimplification, but that’s what you pay for in a free newsletter] as three levels: antibodies, memory B cells, and T cells.
Antibodies are our first line of defense, but they are also the most specific and least flexible. The vaccines target the spike protein that helps Covid enter our cells, and Omicron has many mutations on its’ spike protein. When antibodies work well they prevent us from getting any sort of infection, thus its’ not terribly surprising that Omicron is infecting many people with immunity. Again the specifics of the vaccine give different levels of protection, and the number of antibodies also affects this. This is why when you get a vaccine booster, it jumps the number of antibodies in your blood and helps protect you more.
Memory B cells are the next level of defense. They are far more flexible at identifying pathogens. The more they’ve seen something over a more extended period of time, the better they get. This is why we get a set of shots over several years for most vaccines. This is also likely why those who had a prior infection and are also vaccinated have better immunity.
Lastly [for our discussion], we have T cells. Data released this week shows that T cell immunity appears to be preserved against Omicron. This is a big deal because T cells [along with memory B cells] help prevent significant severe disease. In some sense, Omicron can sneak past the doorman [antibodies], but then the bouncer [B and T cells] finds it and kicks it out.
So what does this all mean for the coming weeks?
Omicron is probably not widely spread in the US. However, we’re still in the middle of a significant winter surge of Delta. Michigan hospitalizations are at an all-time high, with Ohio and Indiana not far from their peaks. Over 8,000 people died of Covid in the US in the last week.
There is limited data that South Africa may be peaking in its’ Omicron wave. This would be great news; a fast-spreading variant isn’t great, but we may avoid long periods of hospital saturation if it subsides quickly.
Given the high level of hospitalizations and death we have today, plus a holiday boost, I am worried about what an Omicron spike in early January could look like for the country. It seems possible there will be saturation of hospital systems in some states. We’ll know a lot more in the coming week or so.
In life, I always think it’s essential to retain some perspective.
Yesterday was the first anniversary of the approval of the first vaccine in the US. Since then, almost 500 million doses have been administered here. Globally nearly 8.5 billion doses have been given.
I remember the relief I felt when the FDA approval came out, that it was the beginning of the end of Covid. Yes, it took a bit longer to roll out the vaccines than anyone would have liked, but the vaccines have helped save lives and get us back to [mostly] normal. In no uncertain terms, we have witnessed one of the great achievements of science and humanity. The Black Death was persistent in Europe for over 200+ years, and we’re going to beat Covid in 2.
While it’s important to remain vigilant against Omicron, we’re in a much better position compared to a year ago.
Obviously, the holidays are coming up. In general, I would strongly recommend gathering with those that have been fully boosted. Also, I would recommend using rapid tests if anyone in your group is high risk. They are cheap and easy to use [takes 15 minutes], and if you test once a day, the chance of spread in a cramped setting is much less. I have not made any changes to my travel plans.
Stay safe out there and, as always, reach out if you have any questions.