Hi, Everyone,

My emails last week about the risk of Covid-19 in young children, and a risk-benefit analysis of Covid-19 vaccines in children and young adults (especially young males), clearly struck a nerve. 

We got hundreds of responses and a lot of thoughtful questions and comments. Although we’re more than 18 months into this pandemic, to some extent, it feels like there are more questions than ever that demand our urgent attention. 

With this in mind, I’ll be dropping back into more analysis and discussion of Covid in these emails over the next couple of weeks—including a follow-up on the risk-benefit analysis of Covid vaccines in younger children (5–11 years old). 

Today, I want to talk about Omicron.

If you only follow the mainstream media reporting on the Omicron variant, you might be terrified. I was going through the airport the other day and saw a TV report about it. While I couldn’t hear what the news anchor was saying, I saw a graphic, which said that Omicron:

  • Is highly contagious and transmissible 
  • Evades existing immunity 
  • Is likely to cause breakthrough infections 

If you take all of that at face value, with no other information, Omicron sounds pretty scary, right?

But let’s take a deeper look at what we know about Omicron so far (along with what we don’t yet know), so we can hopefully come to a more nuanced understanding of what risk it presents. 

Omicron does appear to be more contagious and transmissible

This is apparent from data out of South Africa, where Omicron initially took hold. Omicron appears to have a reproduction number (Rt) of about 3, whereas Delta was about 1.5. The Cleveland Clinic has also reported that Omicron is more transmissible than prior variants, after nearly one-third of 3,000 Covid-19 daily tests conducted by the clinic yielded positive for Omicron.

Omicron does appear to evade vaccine-induced immunity

Denmark has been reporting extremely detailed daily data on Covid cases and hospitalizations, including variants and vaccination status. According to their report from last Friday, December 17, there had been 10,470 cases of Omicron; 79% of those cases occurred in people who were fully vaccinated (2 shots), and 10% of the cases occurred in people who had received a booster in addition to the 2 initial shots. Two percent of cases occurred in people who had received 1 shot. This means that a full 91% of cases were in people who were vaccinated (1, 2, or 3 shots).

We’re seeing similar data out of Ontario, Canada, which has also been issuing detailed reports on cases:

As you can see, there is a steep rise in the number of cases in fully vaccinated people, and this rise is almost certainly attributable to Omicron.

Note that this does not mean that the vaccines aren’t protecting against severe illness—it just means they are not protecting against getting infected in the first place. We’ll need more data to determine the relative effectiveness of the vaccines and boosters in terms of preventing hospitalization and death in various demographics. 

We don’t know as much about Omicron’s ability to evade natural immunity

I’m still waiting to see more data on Omicron infection rates in those who’ve already had Covid-19 (natural immunity). However, previous research out of Israel suggested that those who had recovered from Covid-19 infection were 13 times less likely to be infected with Delta than those who’d been vaccinated but had not yet had Covid-19. This was good news for folks who’d already had Covid-19 and were concerned about getting reinfected with Delta.

While it’s too soon to know for sure, I suspect we’ll see a similar phenomenon with Omicron in this regard.

Omicron seems to be much milder and less likely to cause hospitalization and death

It’s still relatively early, and this could change, but the data that we have from South Africa and Denmark indicate that Omicron is much milder than previous variants. 

For example, in Denmark, there have been 17,659 Omicron cases as of their December 20 report. Yet there have been only 35 hospitalizations and fewer than 5 cases in the ICU (they don’t provide a specific number):

This translates to a confirmed case hospitalization rate from Omicron of 0.2%—which is 80% lower than the case hospitalization rate of roughly 1% from Delta in the UK (I don’t have data on this rate for Delta in Denmark). Note that the actual hospitalization rate is likely much lower because many people with Omicron are not tested and confirmed cases.

What’s more, the number of hospitalizations appears to already be peaking in mid-December, compared to mid-to-late January last year:

To the best of my knowledge, there hasn’t been a single death due to Omicron in Denmark yet, despite almost 18,000 cases. 

South Africa reported a similar trajectory. According to an article on Bloomberg, only 1.7% of those with identified Covid-19 cases were admitted to the hospital during the second week of Omicron, versus 19% in the same week of the Delta wave. That is an 11-fold lower rate of hospitalization for Omicron than Delta in South Africa.

It’s important to note that Omicron has only started to become the dominant variant in some countries in the last few weeks, so we can’t assume that these trends are conclusive or that they will remain consistent.

However, there is reason to believe that they might. According to a fascinating paper out of Hong Kong, researchers found that Omicron preferentially infects the upper respiratory tract and replicates much more quickly. This could explain why Omicron is both more infectious and less severe than previous variants, which tended to infect the lower respiratory tract and replicate more slowly. 

If you haven’t had Covid-19 yet, it’s quite possible that you’ll get Omicron

This is one of those “good news, bad news” things. Because Omicron is so contagious, and because it appears to evade vaccine-induced immunity, if you haven’t had Covid-19 yet, it’s quite plausible that you may contract Omicron. That’s the bad news.

The good news is that, as the data above suggest, Omicron is considerably milder and less dangerous than previous variants and less likely to lead to hospitalization and death. 

When all of this is together, it’s potentially very good news for the course of the pandemic. If SARS-CoV-2 has evolved to become milder and less severe, it could signal that Covid-19 is on the way to becoming an endemic, seasonal virus that is more like the flu or even a common cold than the earlier variants—which had a much higher risk of hospitalization and death. 

You can take steps to improve the function of your immune system

We’ve seen that many people are susceptible to Omicron, whether they are vaccinated or not. Those who have received a booster may have additional protection against Omicron, as some early data (that have not been published or peer-reviewed) from Moderna suggest. And the question of whether boosters make sense may depend on your age and health status—but that’s a subject for another email. 

Given this, it’s crucial that we all take steps to support and optimize our immune system. These include:

  • Eating a nutrient-dense, whole-foods diet
  • Getting enough sleep, exercising regularly, and managing stress
  • Maintaining a 25D (vitamin D) level of 50–60 ng/mL
  • Ensuring adequate intake of vitamins A, C, E, and K2, and minerals like zinc
  • Supporting gut health (since most of the immune system is in the gut) with bone broth, fermented foods, probiotics, and prebiotics

I’ll continue to keep you updated as we learn more about Omicron. 

In health,

Chris Kresser.com

P.S. In mid-January, I’ll be teaching a free class on 3 ways to naturally boost your immune function. Stay tuned for more details!



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