What is the risk of hospitalization with the Omicron variant?

risk omicron variant

There are many people proclaiming that the Omicron variant is “just a cold” or “the end of the pandemic”. Some others on the opposite end of the spectrum are proclaiming that Omicron is the most dangerous variant yet.

This article will not only try to decipher just how severe (or mild) this variant truly is compared to prior variants, but will also review if the vaccines still offer any benefit.

Is the Omicron variant more mild than the Delta variant?

Ever since the Omicron variant was first observed in Africa, many preliminary reports from South Africa suggested that it was milder than the Delta variant that came before it. While it’s true the Omicron variant is milder than the Delta variant, it’s important to recognize that there is a difference between “milder than Delta” and just calling it “mild”.

Now that we have had more data emerge from various parts of the world, we can see that the initial reports were correct:

The reason it’s important to differentiate between “milder” and “mild” is because they mean two completely different things. “Milder” implies that it is being compared to something; “mild” just means it’s mild/non-severe. While Omicron is milder than the more severe Delta variant, it can still cause severe illness.

It’s important to realize that a smaller percentage of hospitalizations among a much larger number of cases is still a potentially large number of hospitalizations. So, the risk on an individual level is lower, but on a societal level Omicron can still be problematic.

To interpret that Omicron is “milder than Delta” as meaning “Omicron is mild” is like if you determined that getting punched in the face is “mild” beauce it’s not as bad as getting punched in the face by Mike Tyson.
One is clearly worse than the other; but both are still bad. There’s a big difference between severity which is relative to something else and just severity on its own.

Is the Omicron variant the end of the COVID-19 pandemic?

Many are proclaiming that the Omicron variant is a sign that the SARS-CoV-2 virus is attenuating (i.e. causing milder illness) and that it’s a sign the pandemic is over. However, this is a premature conclusion to take.

The virus has been evolving since March of 2020; we’ve seen many variants with different characteristics. Some have caused more severe illness, some have spread more easily, and some have been better at evading the immune response. Pundits have said several times that the pandemic was “over”; yet, they’ve been wrong each time.

Yes, eventually they’ll be right…but a broken clock is right twice a day.

The problem is that we don’t know where future mutations and variants will be coming from (since things don’t always happen in a linear way). For example, the Omicron variant doesn’t seem to have emerged from the more recent Delta variant and seems to be more closely related to the Alpha and Gamma variants:

It’s not a simple add-on to the last variant. So, we can’t assume that future variants will derive from Omicron either.
Source: Garcia-Beltran et al.

Can I be wrong? I’m not a virologist or a clairvoyant, so of course I can be wrong (I actually hope that I am)… But one thing I’ve learned since March 2020 is not to underestimate SARS-CoV-2. So, in my humble opinion, we should be preparing for bad news while expecting good news.

Do vaccines still work against the Omicron variant?

It’s important to analyze this question from 3 separate angles: the effect on infections (of any severity), the effect on transmission, and the effect on severe illness (i.e. hospitalizations).

Do vaccines prevent infections (of any severity) caused by the Omicron variant?

When I say “of any severity”, I am including the entire range of infections caused by SARS-CoV-2; from asymptomatic all the way to critical illness/death. So, it’s important to realize that they are all lumped together for this part of the analysis.

One thing that has become clear is that 2-dose vaccination does not prevent infections caused by the Omicron variant as much as it did with prior variants. An unpublished study suggested that the Omicron variant is potentially up to 10 times more contagious than the Delta variant (which itself was much more contagious than the original strain of SARS-CoV-2). That same study also suggests that it’s around twice as likely to cause infections in vaccinated individuals (vaccine-breakthrough infections) compared to the Delta variant. However, since then more data has been released/published.

A study which was published in Cell observed that, while 2-dose vaccines produced a potent immune response against Delta and prior variants, it didn’t mount as much of a response against the Omicron variant. However, they observed that people who had received a booster 3rd dose mounted a potent immune response against the Omicron variant; suggesting that a 3rd dose is important against Omicron.

A study published in JAMA observed that people who received 3 doses were 66% less likely to be infected with Omicron when compared to those who only received 2 doses.

Surprisingly, in that JAMA study, those with 2 doses (if it had been an extended period of time since their 2nd dose) were about as likely to get infected as someone with no vaccinations. Note: this doesn’t address severe illness, more on that later.

Do vaccines reduce transmission of the Omicron variant?

There is little published data looking at the impact of vaccines (and booster doses) on the transmission of the Omicron variant. This is an essential topic to investigate, since this is one of the main arguments for vaccine passports.

The JAMA study cited earlier looked at viral loads in patients infected with Omicron. What this means is that they estimated the amount of virus causing the infection. It could easily be assumed that the higher the viral load, the more contagious you are. In this study they saw that, while 2 dose vaccine regimens didn’t impact the viral load of Omicron compared to unvaccinated people, 3-dose regimens were associated with a lower viral load (approximated using Ct values).

Two separate non-peer reviewed articles from a research group in Denmark analyzed data from Danish households with the initial Omicron variant, and also with two Omicron sub-variants. What they observed was that having a booster dose reduced the risk of passing it on to household contacts by approximately 46% with the initial variant, and approximately 22% with the subvariants.

Surprisingly, the first Danish study also showed that the rates of transmission in unvaccinated households didn’t vary between the Delta or Omicron variant. This adds to the theory that the explosive spread of Omicron compared to Delta is mainly fueled by its ability to better evade immune response in both vaccine or naturally-induced immunity.

So, when it comes to the Omicron variant, the only way that transmission will be significantly impacted is if 3 doses of vaccine are given. This means that 2-dose vaccine passports would not be expected to have much of an impact on transmission.

My opinion: You have 2 choices; either don’t have vaccine passports at all, or you make them 3-dose vaccine passports. Having 2-dose vaccine passports is essentially pointless if your goal is to reduce the spread of Omicron.

Do vaccines reduce the risk of hospitalization with the Omicron variant?

The biggest benefit of the vaccines remains their ability to reduce the risk of severe infections (i.e. hospitalizations). For example, even when the Delta variant was causing breakthrough infections in vaccinated individuals at much higher rates than prior variants, the vaccines were still very effective at preventing severe illness.

A report from the CDC analyzed real-world data to see what the impact of vaccination was on the risk of hospitalization with the Omicron variant:

Vaccination StatusVaccine Effectiveness to Reduce Risk of Hospitalizations
Unvaccinated(used as a baseline for reference)
(received more than 6 months ago)
(received less than 6 months ago)
3 doses90%

As you can see, even with the waning immunity of the 2-dose vaccine series being given more than 6 months prior, there was still significant benefit on hospitalization risk. This significantly increased if the 2-dose series was more recent, and even more if a 3rd booster dose was given.

What is the risk of hospitalization with the Omicron variant?

The Canadian province of British-Columbia has analyzed the data from a period where Omicron emerged. These estimates are not perfect, as they are based on uncontrolled real-world data. However, they still offer a very useful insight into the severity of Omicron. The estimated average risk of hospitalization was approximately 1.2% (as compared to 6.2% with the Delta wave). Because this was an average, the rate will vary according to the person’s baseline risk level; in other words, someone who is higher risk will have a higher rate than 1.2%.

For those who are more visual, check out this excellent graphic prepared by the same group in BC. They show hospitalization risk stratified according to age, pre-existing medical conditions, and number of vaccine doses. It allows to visually show the likelihood of hospitalization according to each factor:

Shows impact of vaccination on risk of omicron hospitalization
Source: Government of British-Columbia – COVID-19: Hospitalization Risk
*Note: estimates only, based on real-world data

Using the table above, we would estimate that a 60 year-old man with 3 risk factors (e.g. high blood pressure, obesity, and diabetes) and only 2 vaccine doses would have a risk of hospitalization of approximately 9.4%. If this same person chose to get a 3rd vaccine dose, his estimated risk of hospitalization would go down from 9.4% to around 5%.

You can also visually appreciate how the benefits of 3rd doses are relative to the baseline risk:

  • In a healthy child there is less of an effect on hospitalization risk with a 3rd dose (since the baseline risk is so low).
  • However, if your baseline risk of hospitalization due to COVID-19 is higher, the benefits of a 3rd dose to reduce your risk of severe illness are very clear.

The Bottom Line

While it’s true the Omicron variant is milder than the Delta variant, it’s important to recognize that there is a difference between “milder than Delta” and just calling it “mild”. This is particularly important for the most vulnerable (especially older adults with risk factors, or immunocompromised individuals).

As we have seen in this article, COVID-19 vaccines can still be very effective; 2 doses don’t seem to protect much against infections of any severity, but they will still significantly reduce the risk of severe illness (i.e. hospitalizations). A 3rd dose not only reduces the risk of infection caused by the Omicron variant, but it also further reduces the risk of hospitalization (especially in higher risk individuals).

Dan Landry

Daniel (Dan) Landry, founder of Rxplanation.com, is an infectious diseases pharmacist at the Dr-Georges-L.-Dumont University Hospital Centre in Moncton, NB, Canada.

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