How Will We Know If Existing Covid-19 Vaccines Work Against Omicron?

With the Omicron variant of the novel coronavirus now detected in 24 countries including the United States, questions are mounting about its potential impact, including how — and whether — existing Covid-19 vaccines will hold up against this latest iteration of the virus. Though much is still unknown about the variant, the World Health Organization (WHO) has reported that Omicron has “a large number of mutations, some of which are concerning,” and that preliminary evidence suggests “an increased risk of reinfection” compared to other variants of concern, like Delta.

But according to Wilbur Chen, MD, an infectious disease physician-scientist at the University of Maryland School of Medicine’s Center for Vaccine Development and Global Health, we’re still at least several weeks away from having answers to our questions about the levels of protection current Covid-19 vaccines offer. 

In addition to figuring out whether a newly identified variant like Omicron will evade the protection offered by existing vaccines, Chen says that researchers also need to determine whether it’s more transmissible and/or causes more severe illness than other variants, as well as whether current diagnostics (like PCR testing) and treatments (like monoclonal antibody therapies) will be effective. 

Essentially, it comes down to how the mutations in the Omicron variant change the behavior of the virus. At this point, scientists know that Omicron shares many key mutations with the Alpha, Beta, Gamma, and Delta variants, but Chen says that alone doesn’t provide a complete picture. “Omicron seems like it could potentially be a beast of a variant,” he tells Rolling Stone. “It could also have all of these features [of the mutations], but then turn out to be a pussycat.” 

According to Chen, it will come down to whether this specific combination of mutations makes Omicron aggressive enough to get past the defense provided by current Covid-19 vaccines. He uses the analogy of humans’ ability to detect familiar faces to explain how mutations can make it harder for a vaccine to work against new variants of a virus. 

“If someone puts on a mustache, glasses, changes their hair — does this or that to change their appearance — the more complex their disguise is, the more difficult it becomes to recognize their face,” Chen explains. “It’s the same thing with the virus: the more complex or [number of] changes there are collectively, the more the body’s immune system — or therapies or diagnostics — just can’t recognize it as well.”

So how will we know whether existing Covid-19 vaccines work against Omicron? Trials are already underway at Pfizer, Moderna, and Johnson & Johnson testing their vaccines against the new variant, Reuters reports, and Moderna CEO Stéphane Bancel has said that the data should be available within two weeks. But Chen says that the data they yield won’t provide definitive answers. 

That’s because these are all in vitro studies — meaning they were conducted in a lab using petri dishes or their equivalent, rather than human participants. “Basically, the in vitro trial data will tell us if the virus is neutralized in the lab,” Chen says. “But that doesn’t really tell us how the human body will actually work to defeat the virus, because there’s also T cells and all the other aspects of the immune system.”

The only way to get that information is to track new Covid-19 infections, hospitalizations, and deaths among the vaccinated — including those who have received a booster dose — in order to determine the level of protection current vaccines offer. “That will take some time, obviously, because it’s something we have to watch over the next few weeks,” Chen says. “And by then, Omicron might be present in many more countries and become the prevalent variant, but that’s the rate at which science can go.”

As much as people would love answers immediately, that’s the process for determining how effective the existing vaccines will be against Omicron. There is no shortcut, and unlike the original Covid vaccine clinical trials conducted in the second half of 2020, it’s not a matter of hitting a certain percentage that indicates whether the vaccine offers sufficient protection against the virus. In the event that researchers determine that a new formulation of a booster vaccine is needed against Omicron, Chen estimates that it would take manufacturers around three months to have one ready to deploy — if all the regulatory and production stars were to align.

In the meantime, Chen says that current vaccines probably offer at least partial protection against Omicron, based on what happened with previous variants. “There have been some declines in the efficacy,” he notes, “but the good thing is that it has not yet resulted in significant declines in protection against hospitalizations and deaths — just mild cases.”

And Omicron aside, Chen urges people to get vaccinated against Covid-19 if they haven’t done so already, and that anyone eligible for a booster get one. Vaccinated or not, he says that it’s important to continue to do what we can to reduce the risk of Covid transmission, including wearing face masks and getting tested often — especially if your holiday plans involve in-person gatherings with friends and family. 

“We need to be mindful that a lot of the actions we take affect other people,” Chen says. “This means recognizing that when you make a decision, you’re not making it just for yourself, but for all the other people that are in contact with you.”

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