"When will life get back to 'normal'?"

That's the question I've asked myself, and been asked by others, a thousand times since the Covid-19 epidemic began.

For most of 2020, my answer was frustratingly vague: Life will return to "normal" when we achieve herd immunity—when 70% to 80% of the population is immune to the coronavirus, whether due to vaccination or a recent infection.

But I couldn't venture a prediction for when that would happen. My day-to-day work researching the virus, available treatments, and supply chain constraints had given me too deep an appreciation for the unknown variables.

Now, finally, things are getting clearer.

I still can't suggest a date when normality will return, but three distinct scenarios are emerging. Call them the "good," the "bad," and the "ugly." In this post, I'll try to pin down the likelihood of each one, and I'll offer specific markers to help you distinguish between them.

Full disclosure: In the week since I began drafting this post, I've had to rewrite it significantly to include encouraging new data from vaccines trials, as well as new risks posed by coronavirus variants. Still, even if these predictions are inherently fuzzy, I think there's value in identifying the futures that could await us—and how health care stakeholders can meet each one.

The 'good' scenario: America achieves herd immunity by summer, primarily via vaccinations

To acknowledge a painful truth, there is no "good" outcome in a pandemic that has already killed more than 438,000 Americans. Yet some of our possible futures are clearly better than others, whether measured by infections and deaths, the suffering of survivors, or the social unraveling of continued social distancing.

The U.S. Covid-19 vaccination scenario planning guide

In that spirit, I hope you'll allow me to describe why a relatively "good" future could be awaiting us—at least in the United States, where I'm most familiar with current trends.

First, vaccinations are accelerating. As of Jan. 1, only 280,000 Americans were receiving a Covid-19 vaccine dose each day. Now, less than a month later, that rate has exceeded 1 million. And it's still accelerating, as Moderna and Pfizer have committed to supply a further 200 million U.S. doses beyond their original plans, and as states grow increasingly sophisticated in their logistics and outreach.

Second, new vaccines are likely coming. We've seen promising—if incomplete—data from Johnson & Johnson, Novavax, and AstraZeneca on their vaccine candidates, which are easier to distribute than existing, mRNA-based vaccines. Together, these companies have committed to provide more than 500 million vaccine doses in the U.S., suggesting we'll have enough doses to vaccinate every U.S. adult in 2021.

Third, the grim truth is that more people are acquiring natural immunity from coronavirus infections. So far 26 million Americans have tested positive for the virus, and some experts believe multiple times as many were infected without a confirmatory test. Nobody knows exactly how long their immunity will last, but they're a growing population with at least some protection.

Fourth, even if new coronavirus variants prove able to infect vaccinated patients, our existing vaccines still seem to prevent Covid-19 from turning deadly. As the New York Times has reported, of the 75,000 patients who received the five major vaccine candidates in clinical trials—including in studies in the United Kingdom, Brazil, and South Africa—not a single one has died from Covid-19.

Finally, spring is coming, and the experience of 2020 suggests coronavirus infections will decline as weather warms. This seasonal effect, when combined with rising vaccination rates, could cause infections to plummet. That, in turn, will reduce hospital and ICU occupancy rates, which will help providers provide top-quality care to each patient, further reducing death rates.

This basic, optimistic scenario is reflected in projections by the well-regarded Institute for Health Metrics and Evaluation. It projects that deaths will decline from their peaks by nearly 35% by the end of February and by nearly 70% by mid-April.

• What defines a "good" scenario? To my mind, a "good" scenario means death rates decline by 90% or more by summer and that herd immunity—perhaps with help from continued masking or social distancing—prevents a major surge in deaths next winter. Outbreaks could still emerge among undervaccinated populations or geographies, but these flare-ups would be far smaller than this winter's epidemic.

• What are the odds? This, I think, is more likely than many people believe. I'd put the odds at 50%.

• How can health care stakeholders prepare? If the U.S. health care system is flooded with newly authorized coronavirus vaccines, our core challenge will be ramping up vaccinations quickly. Our Covid-19 Vaccine Scenario Planning Guide can help you do that. You'll also need to address vaccine misinformation, as well as to meaningfully engage with communities who have deep-seated, and historically well-deserved, mistrust of the health care system. Here's Advisory Board's take on five common vaccine concerns—and how to overcome them.

The 'bad' scenario: America achieves herd immunity in late 2021, in large part due to new infections

America is likely to achieve herd immunity in 2021. The difference between a "good" and a "bad" future is largely about how we get there.

Specifically, in a "bad" scenario, tens of millions of additional Americans will gain immunity the hard way: by contracting Covid-19, with all the morbidity and mortality risks that entails.

Why could this happen? Either because vaccinations progress more slowly than we anticipate, or because the coronavirus spreads more quickly than we expect—or both.

On the vaccine front, it's only too easy to imagine why progress could stall. Perhaps new data halts the authorization of pending vaccine candidates, or Moderna and Pfizer encounter major manufacturing problems, or no vaccine is ever authorized for children or pregnant women. Perhaps vaccine-induced immunity proves to be short-lived, or our vaccines prove less effective than expected on new variants. Or perhaps the U.S. never ramps up vaccinations much beyond today's pace—implying we won't finish vaccinating everyone until 2022.

How 3 providers expanded hospital-at-home amid Covid-19

These risks are all possible. But if there's a reason for optimism, it's that the number and variety of vaccine candidates under development creates resilience against any single failure. In other words, for America's vaccination strategy to fall apart, multiple things likely would have to go wrong.

A separate—and to my mind bigger—concern is that the coronavirus could spread more rapidly than previously projected. This is, in fact, already happening, as more infectious variants that originated in the United Kingdom, Brazil, and South Africa are gaining a foothold in the United States. In northern California, about 25% of cases appear to be linked to a new California variant—and other dangerous variants could be evolving right now in America but remaining undetected.

If these new variants spread faster than vaccinations can occur, then 2021 could be a very difficult year. Further, as the coronavirus becomes more infectious, it will become harder and harder for the United States to achieve herd immunity, since the virus will remain capable of spreading, even with fewer vulnerable targets.

This is the possibility keeping me up at night, and it makes the "bad" scenario frighteningly plausible.

• What defines a "bad" scenario? I'd consider a "bad" outcome to mean: (1) Coronavirus variants drive a new surge in U.S. cases this spring, and we experience infection and death rates that markedly exceed their January peaks; and/or (2) a significant portion of the public remains unvaccinated by fall, and Covid-19 surges as the weather cools.

• What are the odds? I'd estimate a 35% chance. (I'd put higher odds on what we might call a "mixed-bad" scenario, where certain populations receive the vaccine more slowly, leading some communities—especially historically disadvantaged ones—to experience a "bad" future even as others see "good" outcomes.)

• How can health care stakeholders prepare? This scenario implies very high ICU occupancy rates across the next few months, plus the possibility of significant surges next winter. To keep hospital beds available for those who most need them, it will be critical to embrace telehealth, adapt to digital health's "next normal," and ramp up hospital-at-home care.

The 'ugly' scenario: Vaccines falter, and America doesn't achieve herd immunity in 2021

The defining characteristic of an "ugly" scenario is that America fails to achieve herd immunity in 2021. The most likely way this could occur would be if existing vaccines don't effectively protect against new coronavirus variants, or if the immunity conveyed by infections or vaccinations turns out to fade quickly. (We're already seeing signs of this risk in South Africa, where a new variant is reinfecting people who've already had the coronavirus.)

In this scenario, 2021—and even 2022—could look a lot like 2020.

We could see new rounds of stay-at-home orders and lockdowns, more stringent than any put into place since April 2020. The U.S. economy, which so far has been buoyed by hopes of a rapid bounce-back from the epidemic, could crater. Divided political leaders in Washington may struggle to pass relief packages, amplifying the suffering. The failure of early vaccines could lead to a resurgence of vaccine skepticism.

Further, there's suggestive evidence that some of the new coronavirus variants might cause more severe symptoms, which could further overwhelm hospitals and ICUs and cause hundreds of thousands of new deaths. And many people, after years of arranging their lives around an epidemic, could simply give up on social distancing, driving even more infections.

In this scenario, the coronavirus could even become an endemic human disease—the sort of durable, deadly pathogen that wealthy nations haven't dealt with since the middle of the 20th century.

Eventually, our institutions would adapt, and we'd get better at both preventing spread and treating people who become infected. But make no mistake: This is a grim future to imagine.

• What defines an "ugly" scenario? We'll know we're in an "ugly" future if we find it's impossible to achieve herd immunity with current vaccines—whether because our vaccines don't protect against new variants, or because vaccine-induced immunity fades more quickly than we can vaccinate the public.

• What are the odds? It's difficult to say, since the risk depends on impossible-to-know variables such as how quickly variants evolve vaccine resistance. My best guess, however, is 15%.

• How can health care stakeholders prepare? Because an "ugly" scenario could take so many forms, the best way to prepare is to increase your organization's overall resilience. Get ready to boost your surge capacity. Ensure you're ready to meet PPE needs. And make sure you can recognize, and address emotional distress in your staff.

We will live in the future we build

One final thought. For most of this post, I've framed Covid-19's course as something that will happen to us. The world will hand us a good, bad, or ugly future, and it'll be up to us to respond accordingly.

But as people who work in the health care industry—and as members of a shared human community—we also are shaping that future. If we do everything we can to ramp up vaccinations, to engage and overcome vaccine hesitancy, to recognize and contain the spread of Covid-19, and to make social distancing and mask-wearing easier and more acceptable in our communities, we can nudge the course of the epidemic in a more hopeful direction.

A "good" outcome isn't guaranteed, but it's a real possibility—and it's at least partly in our control. We all just need to do our part to bring it about.

Advisory Board's Thomas Seay contributed to this article. Pamela Divack, Anne Herleth, Deirdre Saulet, Darby Sullivan, and Paul Trigonoplos contributed additional research.