Omicron Variant: What We Know About Disease Severity, Vaccine Effectiveness

Gregg Miller, MD, offers insight on the new COVID-19 variant, Omicron, including what we know so far about its severity and ability to evade antibodies provided by existing vaccines.

How transmissible is the Omicron variant compared to other strains like Delta?

When you look at the numbers coming out of South Africa, the transmission curves show that the Omicron peak is rocketing upwards. Their Delta peak came with a much slower uptake.

Even though there is still a lot we have to learn about Omicron, it does seem like this is more transmissible than Delta was, just as Delta was more transmissible than the original, wild type Wuhan variant was.

Does Omicron cause more severe illness? Which populations are most vulnerable to infection or severe symptoms?

There have been some media reports speculating that it might be milder. The honest answer is we do not know, and it is way too soon to tell.

Usually, we have data on the infection curve first. People will start getting infected, and then about a week or two later, we will start seeing hospitalizations, and then a week or two after that, we will start seeing deaths.

We are only a couple weeks into this Omicron curve in South Africa. It is way too soon to know for sure what the severity is, but it is a little concerning that the most recent data that the South African Medical Research Council released shows that there is starting to be an uptick in the number of deaths.

The initial reports showed that hospitalizations appeared to be very mild. People did not know they even had it, and there was not a high demand on oxygen. That has changed. It seems like more and more people are getting admitted to intensive care units and requiring oxygen in South Africa. There is a chance that this will be just as severe as Delta is.

Based on what we know so far, can Omicron evade current vaccines?

Partially. Yes, unfortunately, there is some evasion. This is a glass-half-full-glass-half-empty kind of question.

The good news is there is still some protection offered by our antibodies from vaccination or prior infection. The bad news is that protection is not as robust against Omicron as it was against Delta and the wild type.

Data from South Africa showed a 41-fold decrease in protection from our antibodies against Omicron compared to prior strains. Data from Germany is also suggesting significant reductions in the strength of our antibodies against Omicron.

Pfizer announced that they believe their third booster shot offers as much protection against Omicron as two Pfizer shots offered against Delta. They have not published that data yet, but they have at least made that statement. It will be interesting to see what data they actually have to back that up because some other research is less hopeful about the protections from antibodies.

What we are seeing is that the antibodies do work. They are effective. We just need a whole lot more of them.

The other consideration is that the antibody tests that we have are artificial and done in test tubes, so it does not necessarily reflect our real-life experience with this virus. Our immune system has two different arms. There is the antibody arm, and then there is the white blood cell arm. Even if our antibodies are not as strong against Omicron as they might have been against Delta, our white blood cells potentially still have a lot of power to attack the virus.

White blood cells also have a great ability to generate even more antibodies. Whatever our antibody level is right now, if we get infected, it is going to rise. These lab tests might not reflect what we are going to see in real life.

Odds are there will be a lot of people that have mild breakthrough cases with Omicron. The big question is, will we also see increasing hospitalizations and deaths, and to what degree? We just do not know the answers yet.

There are currently companies seeking approval for oral treatments for COVID-19. Do you think those treatments will effectively reduce disease severity in people infected with this new variant?

Hopefully so. The Omicron variant’s mutations are primarily in the spike protein, which is what antibodies target. These pills, on the other hand, target an RNA polymerase, a very different part of the virus that has a minimal number of mutations right now.

Both molnupiravir and Paxlovid, the two drugs that are up for consideration by the US Food and Drug Administration (FDA), seem to target a nonmutated part of the Omicron variant. It seems like they are going to be just as effective against Omicron as they were against Delta.

How effective is that? We do not know. Initially, molnupiravir seemed to be 50% effective against hospitalization and death. Once the FDA started analyzing the study and we had new data, it seemed to be only 30% effective at preventing hospitalization and death.

Paxlovid was 89% effective at reducing hospitalization and death, at least from the initial studies. The FDA still must pick apart that study and get to the bottom of what those numbers really show. There is a chance that Paxlovid as also not going to be as effective as it first seems.

But the bottom line is: this is very hopeful. If vaccines are not as effective against Omicron, we will very soon have other treatments to help mitigate the impact of this new variant.

Like you have said, it takes a few weeks to understand the severity of each variant. At what point do you think we will understand the full extent on Omicron?

I do not think we will fully understand it until it finally hits us. We are looking to South Africa for guidance right now because that is where it first started, and the South Africans have been absolutely amazing with researching the variant and sharing their data.

But that population is on average 10 years younger than the US population. That population has much higher rates of HIV than the US population. They also have lower rates of vaccination and higher rates of Delta infection. So it is not easy to compare what is happening in South Africa with what will happen in the United States.

We saw with the original variant that certain states are impacted more. New York, at one point, looked very different from the rest of the United States. Most recently, things were terrible in Florida. Now, it is Michigan. We are not going to know what will happen in our own communities until Omicron hits us.

We all need to be prepared, and the important take-home point is that it is really important for all of us to continue to stay socially distanced, to wear a mask, to wash our hands, and especially to get booster shots.

Is there anything else that we did not cover that you would like to add?

I feel like it is depressing when you look at the situation—we wonder why this pandemic will not end. We thought, “once we just get over this Delta hump, it is smooth sailing.” Now, Omicron is here, and what is next after Omicron?

There is very understandable frustration that I and a lot of other health care workers have, as well as the American public. We are done with this pandemic, but it is clearly not done with us.

The message that I want to make sure reaches people is that we are in a much better place in December 2021 than we were in December 2020. We have vaccines. Maybe the antibodies are not as effective as we would like them to be, but the vaccines are still effective. We have some great medications in the pipeline. We have much more widespread access to testing.

The health care system is much more prepared to deal with Omicron. We still anticipate being overwhelmed, but we know how to manage these patients. We have treatment protocols now that we did not have in place last year.

Even though this news about Omicron is not great, I think we are in a better position to handle it right now than we were a year ago.

About Dr Miller

Dr Miller is an emergency room physician and the chief medical officer for Vituity, a medical group that primarily staffs acute care hospitals.