The morning of November 11, 1918, dawned cool and drizzly in France. It wasn’t quiet, though. The Armistice that stopped what should have been the War to End All Wars had been signed before the sun came up, cementing an agreement that the guns on both sides would fall quiet in six hours: with symbolic richness, on the 11th hour of the 11th day of the 11th month. The Allied and German armies cabled their troops at the front to be ready to observe the ceasefire—but they also told them to keep fighting to the end.

Military historians have argued for three generations about why the forces battled on, knowing the war was ending. Did the advancing Allies want to humiliate the Germans? Did the retreating Germans keep firing so as to not haul artillery home? At 9:30 am, Private George Edwin Ellison of Britain died in a firefight, trying to retake ground the German side had already agreed to relinquish. At 10:45 am, Private Augustin-Joseph Trébuchon of France was killed by a sniper while carrying a message between trenches. At 10:58 am, Private George Price of Canada was shot chasing a German patrol through a ruined village.

And at 10:59 am, Henry Nicholas Gunther of Baltimore—once a supply sergeant, recently busted back to private—charged alone toward a German emplacement, leveling a rifle. The troops behind the machine gun reportedly waved him back, yelling that the war was over. When he kept coming, shooting as he ran, they fired on him. Seconds later, as the silence spread, they climbed out of the gun nest, carried his body back to his company, and shook hands. He was the last American, and possibly the last combatant, to die in World War I.

It is almost certain that those soldiers, the last men killed from each of their countries, knew that the end of the war was within reach. They died regardless, out of respect for what they thought was their duty, or out of inattention, or belief.

After a year of a different kind of war, it is difficult not to read their deaths as a cautionary tale. Vaccines have arrived. There is confidence the pandemic can be ended. But for now we have to fight as though the battle continues. We’re likely to be covering our faces and staying home for months yet, and there probably won’t be an Armistice parade where we all throw our masks in the air.

Researchers looking toward the next six months stress that, even though hundreds of thousands of vaccine doses are expected to have been given in 2020, the shots’ effects won’t be visible for a while. That might be because the vaccines are arriving at a time when both new cases and deaths are setting records every day, creating a momentum that will be hard to brake. But the effects might also be hard to see because the first recipients—health care workers and residents of nursing homes and long-term care facilities—live or work in closed systems. What unfolds inside them may not be visible to the outside world.

“I don't think the vaccine is going to make a big impact on cases in the near future—not until there's a significant portion of us vaccinated,” says Nahid Bhadelia, an infectious disease physician and associate professor at Boston University School of Medicine. “However, 40 percent of deaths are coming from nursing homes, among patients who are much, much older and particularly vulnerable. As we cover that population, which is about 3 million people, you may see mortality go down.”

The vaccines authorized so far are not 100 percent effective; the best estimate is that they produce immune responses in 95 out of 100 recipients. But exactly what that response constitutes is still unclear. Researchers are hoping for more data to determine whether they only prevent disease or also prevent infection and transmission to others.

In the most positive interpretation of the data, there could still be millions of people left vulnerable to Covid-19 in the US, because their bodies can’t mount an immune response to the shot or because they are too young to receive it. (The Food and Drug Administration’s emergency use authorization permits the Pfizer/BioNTech vaccine to be used in those 16 and older; the youngest age is 18 for the Moderna vaccine.) Do the math, add in the projected rollout of six months or more, and it becomes clear that the protective behaviors we’ve been practicing can’t be stopped anytime soon.

And that informal equation doesn’t even account for the people who would subtract themselves from it—for outright opposition to vaccination, fear of side effects, or past disrespect of minority groups’ health. The most recent poll done by the Henry J. Kaiser Family Foundation shows that 27 percent of American adults remain reluctant to take the vaccine, and that proportion goes up in minority groups and in rural areas. Distrust can be overcome, says Theresa Chapple-McGruder, a maternal and child epidemiologist working in the Washington, DC, area, but the educational efforts needed to reassure people have been neglected thus far.

“What I've been hearing from a lot of people is, Wait and see,” she says. “I think they're happy not to be first in line. I haven't heard anyone really upset that they haven't gotten there yet and someone else has—outside of politicians kind of jumping the line.”

The calculations of who will be protected and when—and how long it will be until we all are—were further upended just before Christmas by the news that variants of the coronavirus have emerged in South Africa and the United Kingdom, leading to flight cancellations and port closures to keep the more-transmissible version contained. There have been no indications that the variants can’t be contained by the already-developed vaccines, says Angela Rasmussen, a coronavirus virologist and affiliate at the Georgetown Center for Global Health Science and Security. “But the same way to prevent transmission of the variant, if it is more transmissible, is the same way we prevent transmission of every other variant of Covid,” she says. “It’s taking the same precautions: masking, avoiding crowds, no holiday gatherings, and so on.”

If all of this seems to be adding up to a 2021 that looks like 2020: Yes, that’s what the experts predict. Despite the commitment of everyone who participated in social distancing, much of the world is now worse off than in the spring, when lockdowns and mask-wearing first seemed crucial things to do. And vaccines are arriving so heterogeneously that, for some number of months, people who have gotten the shots will be living or working alongside people who are still at risk. A nurse might be protected when her kids have not been; a senior citizen might get the vaccine but be living in a household with fortysomethings who are considered low priority. Until enough people have been vaccinated to establish herd immunity, the safest thing to do is to behave as though everyone is vulnerable.

This is already not happening, says Saskia Popescu, an infectious disease epidemiologist and infection preventionist in Arizona, one of the worst-hit states in the US. “The second the vaccines came out, I've seen a change in behavior, people thinking, Well, it’s over, let’s go back to normal,” she says. “That worries me, because this is going to take a long time.”

But there should come a point at which we cease to be so vulnerable; at which enough people have accepted the vaccine, or have been infected and recovered, that herd immunity is within reach. What will be challenging is that the entire US won’t get to herd immunity at the same moment. The virus peaked in different states at different times, thanks to differences in housing density, age, race, and willingness to practice protective behaviors. Its retreat could resemble its advance.

Public health experts expect that at some point, one of the federal health agencies will propose an algorithm incorporating vaccine uptake in an area, occurrence of cases, and the percent of tests that come back positive. That algorithm will establish a threshold; states that fall below it should be able to relax their protective behaviors. “Every state will have to make a decision,” says Bhadelia. “Different states may meet that standard at different times.”

That means there may not be a single moment that feels right for a national rejoicing—which might not be appropriate anyway, given the hundreds of thousands who have died. And even if we get to that point (one long national exhale, if not one loud cheer), it may only mark a pause. Despite the thousands of pieces of research written in 2020, so much about the coronavirus is unknown: How much it will mutate. If infection creates durable immunity. How long vaccine protection will last. Whether it will be a seasonal risk in the same way colds and flu are. And, crucially, whether enough people refuse the possibility of protection, through vaccination or through masks, to leave us all at risk.

Covid could become something we have to be persistently on guard against, the target of regular vaccinations for children or adults. “Eradication is not in the cards,” says Tom Frieden, an infectious disease physician and former CDC director, now president and CEO of the research organization Resolve to Save Lives. “As with measles or other vaccine-preventable diseases, we're going to see outbreaks that need a public health response. We're still going to need to do testing, isolation, contact tracing, and quarantine, and vaccinate around cases and clusters as those occur.”

So the Magic 8-Ball version of 2021 is: Ask again later. But moving into the new year, there’s one more detail in the story of Henry Gunther that makes his death worth remembering. James M. Cain, then a journalist and later the author of noir crime novels, was serving in the headquarters of the same division, 25 miles from where Gunther was killed. Once military censors cleared the account, Cain wrote for The Baltimore Sun that Gunther had lost his rank because he wrote a letter home that was critical of the war.

Gunther was shamed by the demotion, Cain said, and worried that, because his parents were German immigrants, he was suspected of being a sympathizer. He “became obsessed with a determination to make good before his officers and fellow soldiers,” Cain wrote. “He displayed the most unusual willingness to expose himself to all sorts of risks and to go on the most dangerous kind of duty.”

After his death, Gunther’s rank was restored, and he was awarded the Distinguished Service Cross for bravery. But it is hard not to think that he died because he felt he had something to prove. This pandemic has been propelled by people trying to prove things: that the virus is not real, that rights trump shared responsibility, that evidence is less important than belief. It would be better for us, in the last moments of this battle, to stop trying to prove things, and stay safe in the foxhole, and not fling ourselves in front of the guns.