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The Omicron wave in the United States is upon us. 

If you were fortunate enough to tune out from Covid-19 news over the holidays, you’re coming back to startling reports about record high case counts and, in some places, increases in hospitalizations. The wave will crest, of course; the question is when. 

For now, experts say, the country still has a ways to go to get through the Omicron surge. Below, STAT outlines what Omicron is already teaching us as this phase of the pandemic plays out. 

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A reminder: Scientists have known about this variant for just a little over a month. While a tremendous amount has been learned in a stunningly short amount of time, our understanding will continue to be refined as data pour in and key questions are answered.

The hypothesis that we’re not immunological blank slates is holding up

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When Omicron was first identified in November, there was rightfully a lot of concern about how well protection from past infection and vaccination would withstand the new variant and its multitude of mutations. But many experts took what could be considered an optimistic view: Yes, this virus had changed, but our immune systems still could see it for what it was.

That has largely held true — as protection against severe disease seems to have been broadly maintained.

Omicron can evade immunity to an extent, and our protection against infection has taken a major hit. It’s why you likely know so many people who have been infected in the past few weeks even though they had already had Covid-19 or were fully vaccinated — and even boosted. 

Early studies from South Africa and the United Kingdom have found that vaccine effectiveness from the primary series against symptomatic disease and, to an extent, hospitalization is lower in the face of Omicron than Delta. (It’s also worth noting that some of the vaccines used in other parts of the world seem to be more threatened by Omicron than those authorized in the U.S.) 

But there’s been good news as well. While studies have repeatedly shown that our neutralizing antibodies don’t recognize and block Omicron as well as earlier forms of the virus, our T cells haven’t lost much of a step against the variant, as two studies this week showed. T cell protection can’t prevent infections, but it can minimize the harm caused by the virus — and generally guard against severe outcomes. 

Lab studies have also indicated that a combination of infection plus vaccination, or a booster shot, can largely restore much of the protection that Omicron saps away in people whose immunity is based on having recovered from Covid-19 or having had only a primary vaccine series. Some evidence from the U.K. suggests that the power of boosters against Omicron wanes as well, but that’s against mild infection, not against severe disease.

It’s time to rethink the way we view our metrics 

Brace yourself: Case counts are going to reach astounding heights. Already, reported infections have doubled in just a few weeks. The average daily number of infections is greater than 300,000. (It’s likely that our case counts will become increasingly less reliable as well, given both the shortcomings of our testing infrastructure and the growing use of at-home tests.)  

But, in large part because the immunological landscape today is far different than what it was two years ago, cases are less likely to result in severe disease than was the case at the start of the pandemic. 

Back then, a rise in cases inevitably led to an increase in hospitalizations and deaths. When vaccines went into wide use, those metrics started to become decoupled; cases could rise sharply but hospitalizations and deaths occurred at a lower level than before. In the current phase of the pandemic, the distance between those metrics is growing even greater.

Based on the experience of hospitals in South Africa and the U.K., even the hospitalization numbers alone might get a bit difficult to interpret. As a whole, people who wound up in the hospital for Covid-19 during South Africa’s Omicron spike often weren’t as sick as in the past: they were less likely to need oxygen or intensive care. Clinicians have also found that lots of patients who were in the hospital for reasons other than Covid-19 happened to test positive for the virus — an indication of how widespread Omicron can be. (These patients can still be a challenge for facilities, because even though they’re not hospitalized for Covid-19, they still have to be cared for in Covid-19 wards with the necessary precautions so they don’t infect others.) 

And though the connection between cases and severe outcomes is growing increasingly loose, it’s not completely severed. Infections are going to reach such heights that even if only a small fraction of people need hospital care, in terms of sheer volume, there could be enough patients to swamp already strained hospitals. When that happens, care suffers — and not just for Covid-19 patients. 

This time the crush of cases threatens more than just hospital care

The good news about Omicron is that the overwhelming proportion of cases it causes are mild. The bad news is that it causes so darn many cases, over a short span of time.

Systems — all sorts of systems — struggle to cope when large numbers of employees fall ill at the same time. 

Hospitals that were inundated in the fall with the large surge of Delta infections are once again canceling elective surgeries because of an influx of Omicron cases or an anticipation of the same. In Britain, health authorities are considering turning car parks into field hospitals. This is last-resort level care.

We’ve also seen the impact of Omicron in the disruption in air travel in recent days; airlines simply did not have enough healthy crew members to staff all their flights, resulting in thousands of cancellations. New York City has seen cutbacks in subway service, and first responders ranks have been so thinned by illness that the city has canceled days off for healthy police officers. 

These are still early days in the age of Omicron; this kind of disruption will get worse before it gets better. It could have broad implications — on food distribution, on the ability to keep schools and universities open and functioning, on snow removal after storms, on utility system repairs, on public transit.

Paradoxically, the mildest wave of the pandemic to date may be the most taxing to navigate.

The open questions

For one, there’s the question of whether Omicron — which already accounts for the majority of U.S. cases — takes over completely, or whether Delta can keep a toehold. Two different variants can cocirculate, though a study out of South Africa this week found that an Omicron infection protects against future Delta infections, suggesting that the newer variant might be able to push Delta out for good. 

Experts will also be tracking whether the breakthrough infections and reinfections caused by Omicron can cause long Covid. 

And scientists are still trying to parse what factors — or what combination of factors — explain two of the Omicron era’s defining features: the variant’s enhanced transmissibility and the fact that it’s causing milder illness.

On the transmissibility front, some of Omicron’s spreading prowess clearly comes from its ability to circumvent the immunity of people who have been previously infected or vaccinated. But scientists are still trying to sort out if the virus innately can spread more efficiently than even the highly transmissible Delta variant, which would potentially give it a double edge over its rival. 

And on the severity issue, while it’s clear Omicron has caused milder illness in part because so many of those being infected have some level of immunity, there are clues that other factors could be at play. Some lab studies suggest that the variant, which excels at infecting cells in the upper respiratory tract, struggles to target the cells deeper in the lungs. That research supports the idea that the variant is also intrinsically less likely to cause severe disease than other variants. (A reminder that even a “mild” Covid-19 case can leave people feeling quite sick; it’s just that they can ride it out at home.) 

Finally, a key question relates to how long we’ll be in Omicron’s grasp. South Africa’s bellwether wave soared to extraordinary heights — then quickly began to ebb. Data from several European countries also suggest that Omicron waves may be short, sharp shocks compared to the waves that have preceded it. But too little is yet known to predict with any confidence whether the experience of a country with a relatively young population, such as South Africa, will hold true in a country with an older population, such as the United States.

Stay tuned.

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