A forecasting model from a Brown University epidemiologist predicts that Rhode Island will see record high COVID-19 cases and hospitalization as early as this week. Health reporter Lynn Arditi spoke with John P. Fulton about the models he and his colleague at Brown’s School of Public Health developed for the state Department of Health. Dr. Philip A. Chan, who works with the department, joined their discussion. 

Arditi: If your projections hold true, it looks like in the next week or two, Rhode Island will experience the highest number of virus cases of the pandemic ever. What's going on and why now?

Fulton: That is true, we do believe that we will peak in the next one or two weeks. By the way, this is what we're seeing from elsewhere in the world. The Omicron wave, which is really the fifth wave of the pandemic, is a fast one. It comes quickly and leaves quickly. This is opposed to, for example, a wave that took months to develop in late 2020 and only broke after the holidays. So we believe this will be a quick wave.

Now, what's going on is pretty simple. First of all, we do believe that Omicron is more easily transmitted than previous variants. It has genetic characteristics that permit it to be transmitted more easily than previous variants. However, another very important reason that Omicron is being transmitted apparently as quickly as it is, is because it can see many more susceptible people than can Delta at this point. And the reason for that, the reason many more people in Rhode Island were susceptible to Omicron, than to Delta is, as we all know, the concept of what we call loosely ‘immune escape’, which means that immunity that people had to previous infections did not hold as well, under Omicron. 

Arditi: So we have a more infectious virus. Our vaccinations aren't holding up as well against Omicron. And we still have about 250,000 Rhode Islanders who are either not vaccinated or have not had the virus. And even if they've had the virus may not be protected because of the way Omicron works.

Fulton: That is correct. With one additional fact. At the beginning of the Omicron wave we believe that slightly more than 500,000 people were susceptible to Omicron. That means a lot more people, a lot more people were vulnerable. Let me let Dr. Chan weigh in on this stuff.

Chan: Thank you, Dr. Fulton and Lynn. I just want to highlight that these models are rough approximations. These models are based on a number of inputs, and there's no way that we, in any pandemic can accurately capture all the complexity of the inputs and behaviors of how the pandemic is playing out.

Arditi: Describe for me what the model shows about hospitalizations rising and how it compares to the past waves.

Fulton: In terms of sheer numbers, the rise in hospitalizations is beginning to rival the wave that we had at the end of 2020. The number of hospitalizations per day is high. Between again, on average somewhere between 50 and 60 new hospitalizations a day. In the past week or so that's high. But one of the problems, of course, for the hospital is not just that people are admitted, but that they stay. So that length of stay is also an important factor in this. What we're seeing is that the rise in hospitalizations, as a proportion of cases, is much lower than it was certainly under delta and previous variants. Nevertheless, the ratio of or the proportion of cases that we have been able to count that end up in the hospital is considerably less, perhaps a third under Omicron, as it was say, say under Delta.

Chan: To highlight what Dr. Fulton mentioned, is with the infectiousness of Omicron, yes, we may see less hospitalizations due to Omicron. But the sheer number of increased case counts that we're seeing, coupled with still the significant risk of severe illness in certain groups – older people immunocompromised, those with other health conditions – does have the potential to overwhelm our healthcare system, which is what we're seeing now.

Arditi:  So early in the pandemic, we were all looking at national models that predicted that hospitalizations were going to rise way beyond what we ultimately saw, as the pandemic began to play out. What did we learn from those mistakes and modeling and have those mistakes or miscalculations sort of informed? What we're doing now, what you're doing John Fulton,  with your models?

Dr. Fulton: I think initially, we did not take the sort of the natural response, not only of the government but also the individuals, to an increase in cases into account.  Now, what we've discovered, of course, is that when people shelter, when we close something down, when we put masks on, when we vaccinate people, and so on and so forth, we reduce the susceptibility of the population as a whole. And what we've discovered over time, is that there's a natural, sort of almost an ecological process, in which when things go up, people's behavior changes, they have for the most many people take precautions not to be exposed. And so the…what is going up, then begins to come down. So for example, built into my model is a certain amount of mitigation. And as an example, we reduced, I reduced the mitigation that had been built into the model, my model, I reduced it as we got into the holidays. And then I've increased it again, as we've left the holidays. Knowing that during the holidays, people were including myself, were going to perhaps take more risks, 

Arditi: I'm wondering now thinking, maybe I should, you know, stick close to home this week and not socialize too much. But I'll wait for another week or two or till mid February to do that.

Fulton: You know, if you were to isolate yourself, for example, some people are of course, and then come out in the middle of February things would be better in the middle of February because we would have perhaps immunized 90,000 more people.

Health Reporter Lynn Arditi can be reached at larditi@thepublicsradio.org. Follow her on Twitter @LynnArditi