What does history tell us about how a pandemic ends? Cases of COVID-19 continue to decline, vaccination rates are rising and people everywhere, including on-campus, are beginning to resume everyday activities. In this Q&A, Kimberley Shoaf, a professor in the Division of Public Health and director of the health and safety branch of the U’s COVID-19 task force, shares insights into what to know as we enter this new phase of the pandemic.

Based on the past, where are we in the span of a pandemic?

If we look at the 1918 pandemic, it didn’t really end until April 1920. It had a very high case and mortality rate, infecting about one-third of the world’s population in four waves. About 500 million were infected and up to 100 million died. But there was no vaccine in 1918. So many people were infected or died that the virus’ spread was curtailed and it became an endemic health issue—just another one of the seasonal influenza viruses that resurface every year. Every year, about 30% of the population either gets influenza or a flu shot, which slows down its transmission.

Another example is the H1N1 pandemic, which started in April 2009 and continued as a pandemic through February 2011. Today, the H1N1 virus continues to circulate as part of our normal seasonal flu virus. Again, annual influenza vaccines help to keep this under control.

At this point with the novel coronavirus, we have had about 160 million cases of COVID-19 globally—about 2% of the world’s population—and we’re saying 3 million have died. We are not going to reach herd immunity naturally, through infections or deaths, so that is not how we are going to end this pandemic.

But we have vaccines, which is why we think we can get this pandemic under control.

What is the scenario experts expect to see going forward?

Most experts think coronavirus will stop being a pandemic because it will stop having this explosively infectious spread due to population exposure and vaccinations. But it will continue to be a virus of concern for us because it is not going to go away entirely. It will stop being a pandemic when we no longer see surges in cases—and not just in the U.S. It only stops being a pandemic when it stops being a global problem.

If we achieve herd immunity here in the U.S. but don’t achieve that level of immunity around the globe we’re going to continue to have problems.

What can we do to reach that goal?

Get vaccinated. If enough people are vaccinated, the virus can’t be transmitted and even people who are not vaccinated are protected. Let’s say that of 10 people, eight are vaccinated and two are not. That means only two people are vulnerable to becoming infected. That slows the transmission rate way down so that eventually, fewer and fewer people are getting infected as the virus tries to make the rounds.

In Utah right now, 1.2 million people are fully vaccinated; including those who have received at least one dose brings that number up to 1.4 million. That’s just over 38% of our population—which does include many children who are not eligible for the vaccine because they are under 12 years of age. We need about 70% of all Utahns to get vaccinated. Because children under 12 aren’t yet eligible, we need to get most Utahns over age 12 to get vaccinated to reach that point.

What’s a simple explanation of herd immunity?

Herd immunity is based on population and how many people may get infected by a person carrying the virus. Herd immunity is reached somewhere between 70% and 80% of the population either having had COVID-19, and thus acquiring some initial natural immunity, or being fully vaccinated.

One concern is that we are just over halfway to 70% and vaccination rates are slowing. The mask mandate has now been rescinded, though a lot of people are still wearing masks, and many people are still physically distancing and working remotely. We are just beginning to see the return of large in-person events. All that is helping to keep positive case numbers down.

But again, an example of what can happen as we start to resume regular activities. Imagine a room of 100 people, one of whom has coronavirus. Twenty people in the room are fully vaccinated. That leaves 80 people at risk of exposure.

While our case numbers are looking better, we’re about at the same case count as we were a year ago. We could see cases continue to plateau or, if we don’t get a significant increase in people who are vaccinated, begin to climb again as everyday activities resume. I don’t think it will go back to levels we saw in December and January, but it could be like last October and November.

If we could reach 70% of adults being fully vaccinated by July, we would be in very good shape, especially since we’ve opened vaccinations to children ages 12 and older.

And then we might be able to call the pandemic over?

The future possibilities are eradication, elimination or management.

 It could be we eradicate it as we did with smallpox. That is the only disease we have completely eradicated and we were able to do it because only humans can be infected by smallpox. Once we stopped the transmission in humans, it couldn’t mutate or be transmitted.

With extremely high vaccination rates and possibly regular boosters, we could achieve elimination. That means that we’ve brought the numbers down so that we rarely see a case.

We’ve gotten there with polio in most places in the U.S. It is no longer a problem because nearly everyone gets vaccinated and that helps prevent sickness in those who aren’t vaccinated.

What’s more likely here is the novel coronavirus becomes endemic, which means it occurs at a fairly regular rate in the community and becomes a part of the normal seasonal diseases like influenza. But because so many people are vaccinated, it is less deadly. Hopefully, as we get more and more people immune and not able to be infected or at least at lower levels, we will be able to live with it at an endemic rate and it will be just another coronavirus like the ones that cause colds.

It also could get to the point where it is like influenza and becomes part of normal seasonal diseases but because so many people are vaccinated it is less deadly. Hopefully, as we get more and more people immune and not able to be infected or at least at lower levels, we will be able to live with it at an endemic rate and it will be just another coronavirus like the ones that cause colds.

I can guarantee we won’t get to eradication, but we could get to elimination like with polio. That would take a lot of work and high vaccination rates. It is more likely that this coronavirus will become endemic and we will be able to control it through vaccination. It is possible that we could have mini-epidemics, where it simmers along and then flares up for a time. We see this with many other vaccine-preventable diseases such as measles.

In this most likely scenario, we need more treatments, so that just like when you get influenza you can take Tamiflu and not have a severe case. If we get a treatment like that—and they are working on one in trials right now—that helps us break transmission and reproduction in the body, we can manage it. And that is probably what will happen: We will manage it through vaccination and treatment.

As for variants, the more people who are vaccinated, the fewer people get infected and thus there is less opportunity for mutation of the virus.

But remember: The pandemic is not going to end for us until it ends for everybody. We need the entire globe to be on board with this. The first step is to make sure we are all vaccinated and the second step is to make sure people in other countries are, too.