August 4, 2021 by Suzanne Judd, LHC Director

I think I speak for all of us when I say that we had all hoped to be on the path to freedom from COVID-19 by now. Surely, Americans everywhere would like to move on in whatever ways they can – family gatherings, community events, concerts, travel, and so many other things that we’ve been missing for well over a year now seemed within reach just a few weeks ago. Unfortunately, it seems that what progress we had made in overcoming the pandemic is at risk, and we may have to wait a bit longer before we can truly be free from the virus.

Beginning in early June, there were indications in Missouri that we hadn’t quite made it out yet. The delta variant of SARS-CoV-2, the virus that causes COVID-19, began to circulate and cases spiked quite rapidly. As a localized outbreak, the outlook for the rest of the country wasn’t too bleak. However, it wasn’t long until the variant spread down to Florida and the Gulf Coast. Here in Alabama, we are now seeing exactly what it means to have a surge in cases from the delta variant. The figure below uses statistical modeling to predict how many cases we may observe from this new surge.

Figure 1.  Actual Epidemic Curves Observed in Alabama and 3 Predicted Curves for the Third Surge. The Alabama rate assumes cases will continue to grow at exactly the same rate as what is currently being observed in Southern Alabama. The India curve assumes the cases will grow in a manner similar to India from April to July 2021 and the United Kingdom (UK) curve assumes cases will accrue at the same rate as the UK observed this summer in a 70% vaccinated population.
Updated August 10

What do these data mean for hospitalizations?

One piece of data that has become clear is that the vaccine helps to keep people out of the hospital, even if they develop mild symptoms from exposure to a person who has COVID. UAB Hospital has recent recently reported that over 95% of the people hospitalized with COVID-19 had not yet received the COVID-19 vaccine. Since Alabama only has about a 40% vaccination rate right now, this leaves many people at risk of being hospitalized.

Figure 2. Estimated Hospitalizations Assuming the Middle Path (India Model). COVID19 Epidemic Curve in Alabama – Estimated Cases Based on Epidemic Curve from India Apr-June 2021 and Corresponding Hospitalizations in Alabama.

What about missing work, school or other activities?

The Southern Alabama curve allows us to estimate the number of people who would be infected, quarantined, or in the hospital at the peak of the surge. If the entire state begins to surge at the rate Southern Alabama is currently surging, there would be about 20% of the population out due to either illness or quarantine for 3 weeks centered around August 26. This assumes that each sick person would come into contact with about 5 other people who would have to quarantine. It also assumes isolation and quarantine to be 14 days. It is really challenging to estimate the number of contacts a person may have or the potential impact of a whole sports team, classroom, or congregation in quarantine. It is possible that 30-50% could be out at one time depending on how people were exposed to an infected individual.

Table 1. Outcomes of Various Transmission Rates
Updated August 12

What can be done?

Absenteeism could be reduced by 37% if masking were required in schools while COVID is circulating at high levels.  Masking would reduce absenteeism to between 6% and 14% in the setting where 5 close contacts have to quarantine. In the case where large groups (classrooms, teams, choirs) have to quarantine, masking could reduce absenteeism from 50% to 37%.

Higher levels of vaccination will have lower levels of absenteeism, since vaccinated people with no symptoms do not have to quarantine and the biggest driver of absenteeism will be quarantine (accounts for 80% of the absenteeism). This has a direct impact on the faculty and students over age 12. It could keep faculty from having to quarantine due to an exposure in their classroom, which will reduce faculty absenteeism.

A school with 90% of the faculty vaccinated would have an absenteeism rate among the faculty of 1% at the peak of this surge compared to 19% in a school with only 10% vaccination rate. The same is true for classrooms where children are 12 and older.

How will we know which of the 3 curves Alabama is on?

The curves above are only predictions. There is uncertainty in the models so it is important to regularly check the data to see how the models are performing. Actual case data can be used to examine how well the model is predicting hospitalizations in Alabama. The figure below shows how well the models are tracking with the number of hospitalizations reported each day. Currently we are much closer to the Southern Alabama path than the India or UK paths but masking, reducing social activities, and increasing vaccinations will all help to bend the curve down so that we do not stay on this path.

Figure 3. Number of Hospitalizations Estimated by Each of the Three Models vs Actual Cases through August 9.
Updated August 10