COVID-19 and Vaccination Rates: Answers from a BYU statistician

In this Q&A, BYU Academic Vice President and statistician Shane Reese discusses the complex numbers behind COVID-19 and vaccination rates. Prior to his appointment to the President’s Council, he served as dean of the College of Physical and Mathematical Sciences and has been a member of the Department of Statistics faculty since 2001. He is an elected fellow of the American Statistical Association and prior to coming to BYU, he worked in the Computer, Computational and Statistical Sciences Division of Los Alamos National Laboratory. He is a current member of the university’s policy group, which is responsible for making health and safety decisions for the campus community during the COVID-19 Pandemic.

Q: There have been a lot of numbers reported during the pandemic, from case counts to hospitalizations to vaccinations. Which numbers should I pay attention to?

A: Starting where we are in the pandemic right now, there are two numbers that carry the most weight: vaccination rates and ICU hospitalizations — especially the number of COVID-19 patients occupying ICU beds. Of course, case counts still matter, but they mattered even more at the beginning of the pandemic before, as President Russell M. Nelson said, we received a literal godsend in the form of the vaccine. The higher the vaccination rate and the lower the number of hospitalizations, the better shape we are in as a community to have sufficient health care resources to navigate the pandemic. As we’ve said before, we strongly urge students, employees and campus guests to get vaccinated.

Q: What information do BYU decision makers review in considering regulations and restrictions on campus?

A: Here is the short list: Case counts on campus, campus vaccination rates, hospitalizations (including ICU hospitalizations) in our community, deaths in our community and case counts in our community. While we certainly want our true vaccination rate to be as high as possible and our case count to be as low as possible, there currently is not a magic number that would dictate any adjustment to a course of action. The delta and other variants, such as lambda and mu, have added to the complexity of assessing the safety of navigating this pandemic because they bring the reality of breakthrough cases.

Q: Speaking of vaccination rates, how does one determine accurate vaccination rates?

A: When you think of a vaccination rate, you are typically talking about the percent of the total population that has been vaccinated. We know there are two key numbers when determining a percentage: the numerator and the denominator — and it’s critical to have both numbers right. Your percentage, and therefore your vaccination rate in this case, is only as accurate as your numerator and denominator. Some entities report the number of people vaccinated over the number of people eligible to be vaccinated. Those “eligible” may not include those who are exempted from vaccination for religious, medical or even personal reasons. From a public health perspective, the most accurate numerator is all those who are vaccinated in your population and the denominator should be the total number of people in your population, whether or not they are “eligible” to be vaccinated.

Q: What is BYU’s reported vaccination rate and how is it determined?

A: BYU’s current vaccination rate for the full campus community is 75% fully vaccinated, which jumps to 80% if you include those who are partially vaccinated. Roughly 16% are unvaccinated and another 4% have yet to report their status. (The vaccination rate for employees is even higher: 79% fully vaccinated; 82% with at least one shot and just under 9% unvaccinated, with 9% unreported.) We calculate the full campus vaccination rate by including all students, faculty, staff, administrative employees and part-time employees, and put them in the denominator. Those who are exempted from vaccines are still included in the denominator since they are still in the community and have the ability to spread the disease. Then we look at those vaccinated in that group, and that becomes the numerator in that equation. From a public health perspective that is the true vaccination rate.

Q: Doesn’t everyone report vaccination rates the same way?

A: Not always. If someone receives a valid exemption, it’s sometimes hard to determine if they should be counted in that denominator. As I mentioned earlier, some choose to report their vaccination rate by excluding all of those with exemptions. One of the things I teach in my Statistics 121 class is the need for students to be savvy consumers of the numerical or quantitative data they receive. There have been reports of 100% vaccination rates, and if that was true, then it would obviously provide a huge protective influence. Often an extremely high vaccination rate was calculated excluding those with medical, religious or personal exemptions. To have a better picture of what that rate means, it is imperative to also include the percentage of those exempted. I recommend anyone looking to determine the accuracy of a vaccination rate dig a little deeper to see what data are being used to produce the final figure.

Q: How do vaccine mandates impact vaccination rates?

A: Vaccine mandates when implemented properly can be good tools for managing COVID-19 spread. One benefit of a vaccine mandate would be a more formal reporting process and improved accuracy of vaccination rates. However, as many are aware, public institutions of higher education in Utah are subject to House Bill 233, which allows them to require vaccine mandates as long as they allow for medical, religious and personal exemptions. That personal exemption is a pretty broad class. As a tool for managing COVID-19, a vaccine mandate becomes less effective when it has to allow for those exemptions.

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Read more about BYU's COVID-19 protocols and policies here: https://www.byu.edu/coronavirus/