Risk management in the pandemic: Don’t put all your eggs in one basket

Ashley Kilgore:

Even with the COVID-19 vaccine readily available throughout much of the country and the age ranges of those who can receive it expanding, research shows that in the face of a new wave or variant of the coronavirus, the tools that we use at the onset of the pandemic, masking and social distancing, are still key to helping mitigate the spread of the virus.

Ashley Kilgore:

Joining me to share his research to help develop a model for social distancing policies to prevent surges in new cases and hospitalizations is Dave Morton with Northwestern University. Dave, it’s great to talk with you. Thank you so much for joining me to share your work.

Dave Morton:

Hi, Ashley. It really is my pleasure.

Ashley Kilgore:

Obviously these surges of the coronavirus are accompanied by an increase in hospitalizations that have an incredible impact on hospital staff and resources. Can you share some insight as to the scope of the impact that just one of these major surges can have?

Dave Morton:

Yes, absolutely. Licensed beds in a hospital … They don’t mean a heck of a lot unless we have trained medical personnel to staff those beds. This really has been an issue throughout the pandemic, but it’s especially a pressing issue right now. The CDC indicated that one of the reasons they reduced the isolation and quarantine period from 10 days to seven and then to five had to do with shortages in healthcare personnel. Some states are saying that a healthcare worker who’s asymptomatic, they can go back to work as long as they’re masking, and I think that’s really a striking indicator of how much stress is being put on our medical personnel.

Ashley Kilgore:

So Dave, to build on that I imagine as we’ve experienced multiple surges throughout the pandemic accompanied by reports of hospitals filled to capacity, the cumulative effect must be quite significant. I know here in the Maryland, DC area, it’s been reported that the omicron surge alone saw record-breaking hospitalization numbers and that’s after the delta variant and previous waves of the virus also resulted in new surges in cases.

Dave Morton:

You’re right. Under delta, we saw longer ICU durations and that strained nurses and physicians, and during Omicron with its transmission and its evasion of prior immunity, we’re seeing more sickness and increased hospitalizations and that includes illness among hospital staff.

Dave Morton:

You mentioned the cumulative toll. I think the toll on mental health, including that of our healthcare workforce and other frontline workers, has been really a strain on the system. I think this is one of these times where you really need to step back and look at the larger system.

Dave Morton:

We have strained supply chains that stock our hospitals. Our healthcare workers, they have families, so when their kids can’t be in school or in daycare, there’s an illness in the family, that further strains the system. What happens to patients when they’re discharged? Well, some of them go to long-term care facilities or nursing homes or assisted living facilities. When they can’t take discharged patients because of illness or staff shortages or supply chain issues, that just puts further strain on our overall system.

Ashley Kilgore:

Dave, even now here at the INFORMS office in Maryland, we are once again masking indoors and maintaining social distancing as the omicron variant of the coronavirus continues to cause a surge in cases here. Why do social distancing and masking remain such important tools even with the vaccine?

Dave Morton:

I think it’s first important to acknowledge this is exhausting. We’ve hoped to be done with COVID multiple times. Uncertainty in general is hard and uncertainty on this scale is enormously hard. We know, especially in our community, that when it comes to managing risk, you don’t put all your eggs in one basket. That is, we shouldn’t put all our eggs in the vaccine basket. So we really do need to invest in multiple tools, and that includes testing, the kind of community mitigation strategies that you mentioned as well as vaccines and boosters.

Dave Morton:

When it comes to these community mitigation strategies, we know that they work. If you look at masking and social distancing, washing your hands and staying home if you’ve had symptoms, they reduce transmission. This isn’t new. We’ve known this. There are studies for example, from the 1918 influenza pandemic that are city by city and established this.

Dave Morton:

I think another big part of this is, so the initial regimen of vaccine and subsequent boosting, they reduce the most adverse outcomes in terms of hospitalization and death, but new variants like omicron, they can evade prior immunity. We also know that efficacy wanes over time and that includes in transmission. Early on in the pandemic, we had a real problem because transmission would occur before the onset of symptoms. Now, the effectiveness of vaccines in reducing even milder symptoms, this again can lead to effectively asymptomatic transmission, and that’s why using these nonpharmaceutical interventions is so important.

Ashley Kilgore:

So now you’ve been working to create social distancing policies that take into account a number of unique factors and could help minimize these hospital surges and their impact. Can you tell us a bit about your work in this area?

Dave Morton:

The basic premise of our work is that we should not allow overwhelming surges of hospitalizations, which compromise our ability to care for patients. If you accept that premise, then there are two natural questions that come up. What indicators should we track, and when should we act in order to tighten or loosen nonpharmaceutical interventions?

Dave Morton:

In terms of the first question, so what we do is we track the seven-day moving average of COVID hospital admissions, and this was an intentional choice. There are lots of things you could track. Deaths are a lagging indicator … Actually so is the hospital census, that is heads in beds. Treatment protocols have improved over time. You could test the positivity rate. You could track that, but that’s really less reliable because the availability of tests has changed over time. Who’s being and why has also changed over time. So that’s why we track this seven-day moving average of COVID hospital admissions.

Dave Morton:

To answer the second question, what we did is we built an optimization model on top of a mathematical model of disease transmission. So this answers the question, when should we act? That is, when should we enforce stricter social distancing measures? We do that when the seven-day moving average exceeds certain trigger thresholds, which we optimize.

Ashley Kilgore:

How does this approach differ from some of the existing guidelines as far as social distancing and sheltering in place?

Dave Morton:

Our system is what’s called a staged alert system, and these systems they’re just absolutely pervasive. If you look in cities across the US, there’re some US states that have a staged alert system and then that gets tailored to local conditions, for example, at the county level, and they’re used worldwide.

Dave Morton:

However, most of those systems, they don’t really explain why they chose the rules that they did. Systems that are used in practice, I think what makes our system unique is that we’ve rigorously derived these threshold triggers that cause changes in the stage, whether it’s the red stage, orange stage, yellow and so forth. What we do is we use observed hospitalization data and we use our mathematical model of COVID transmission that’s been calibrated to the hospitalization data, and then our optimization model says we want to be 95% sure that we don’t violate hospital capacity. We’ve been particular focused on ICU capacity. Then, given that we satisfy that, we want to minimize the expected number of days that are spent in the strictest stages of social distancing.

Ashley Kilgore:

Dave, could you share a bit about how your research has been utilized so far?

Dave Morton:

Our system has been operational in the metro area in Austin, Texas, which is about two million people, since May 2020. The Mayor, Steve Adler, Austin’s Chief Medical Officer, Dr. Mark Escott, the Public Health Authority, Dr. Desmar Walkes, they’ve really been instrumental in socializing our system really from day one, getting community buy-in and then informing residents of an impending surge.

Dave Morton:

Our system’s been repeatedly pressure tested, and we’ve updated it when delta or omicron comes along, when there are changes in ICU capacity. The success of our kind of system really hinges on community adherence. What’s happened when hospitalizations have risen? The community can see that on this public facing dashboard. They see that from tweets from Austin Public Health and other social media avenues, and they see it through news coverage. The residents in Austin have responded extremely well.

Dave Morton:

It’s really hard to change the behavior of a large community kind of on a dime, and efforts to get buy-in early were really key. If you look at COVID deaths per 100,000 in Austin, they’re less than half of that in Texas or the country as a whole. When you think about our hospitals, people are going to the hospitals for surgeries, for everything from hernias, cancer, an appendix being removed, hip replacements and so on. Austin has spent the fewest days of the major cities in Texas in restrictions on these so-called elective surgeries. So in short, I think our system has worked pretty well and worked as designed.

Ashley Kilgore:

Dave, thank you again for joining me and for your contributions towards combating the pandemic. Any final thoughts to share with our listeners about the unique insight you’ve gained from your work?

Dave Morton:

One thing is I’m extremely grateful for our team of researchers. This is PhD students, post docs, undergraduate researchers, faculty collaborators from Northwestern and from the University of Texas at Austin. They’ve really done actionable, quick turn analyses that have allowed policy makers to be decisive, and it’s really countless hours of groundwork that have made those quick turn analyses possible.

Dave Morton:

I guess the other thing is I’d like to emphasize this really is all about people. We can formulate and calibrate our mathematical models, but for them to work, of course we need researchers like our team and so many others across the country and around the world. We really need committed leadership from cities, from states, federal officials. We really need our community to think about and to value and to act for the benefit of all of us in including the most vulnerable in our community.

Ashley Kilgore:

Want to learn more? Be sure to check out the show notes, posted in conjunction with ORMS Today Magazine online to learn more about what was discussed in this episode. The podcast is also available for download from Apple Podcasts, Google Play, Stitcher and Spotify. Wherever you listen, please take the time to do a review, as that helps other listeners find the podcast. Until next time, I’m Ashley Kilgore and this is Resoundingly Human.