How Will Vaccination Impact Dane County’s COVID Metrics?

Now that a highly effective vaccine is making its way into arms across the country, the question of “When will it be time to go back to normal?” is asked with more regularity (and hopefulness!). Dr. Anthony Fauci, the nation’s senior official for infectious diseases, predicts herd immunity by the end of summer, with fall seeing “some form of normality.”

We know there are many steps between now and “normality.” People want to know what will happen in order to have time to plan and prepare for what is next. And yet, the one constant in this pandemic has been unpredictability.

Throughout the pandemic, we have relied on a set of metrics to help us understand what is going on. Cases per day, percent positivity, and people hospitalized with COVID are some of the key indicators we’ve used to make decisions on county-wide policies for the prevention of spread.

When we established these metrics in early 2020, there was a hope that the pandemic would progress in a straightforward manner—we’d buy time for our health systems by flattening the curve, and then we would gradually re-open society in a stepwise manner as the virus got more and more under control. This has not been the case. Instead, the “new cases by date” curve looks more like a roller coaster—a fitting analogy given the ups and (many) downs of 2020.     

While these metrics still help us understand current virus dynamics, different variables are going to be important moving forward, such as:

• The proportion of our population that is vaccinated
• The speed at which people are being vaccinated
• The level at which the virus is circulating (which may be impacted by variants of the virus that make it easier to transmit)

As we have done at every stage of the pandemic, we are reviewing the scientific literature to understand how these factors may impact the course of the virus over the coming months. We want to know what to expect as more people are vaccinated. Because we’re only a month into COVID vaccination, there aren’t many answers out there yet. What does exist is based on models, which can be helpful but should be looked at with some caution.

One model, developed by a team that included the new CDC director Rochelle Walensky, looked at how quickly we could get the pandemic under control under different scenarios of how fast the vaccine is administered to the population and how much the virus is circulating. A few takeaways:

• When the infection rate—the average number of new infections resulting from a single infection—is low, vaccination will have a greater impact.
• The faster the population gets vaccinated, the more infections will be avoided.

According to this model, when 0.5% of a population is vaccinated each day, and the infection rate is 1.5, it would take 100 days to reduce the number of new infections by around 80%. This model does not take into account the proportion of the population that may have some immunity due to prior COVID infection, nor does it account for the new variant.

How might this model apply locally? To answer that, we’ll look at a few questions:

What is the infection rate in Dane County? 
You can monitor Dane County’s infection rate on COVID Act Now. As of now, Dane County’s infection rate is 0.89, meaning on average, each person with COVID is passing it to fewer than one other person.

What is the current rate of vaccination in Dane County?

As of January 22, 44,912 doses were administered to Dane County residents. 11,207 people (2.1% of the Dane County population) have been fully vaccinated, and 22,498 (4.1% of the Dane County population) people have had one dose. 33,705 people (6.2% of the Dane County population) have had at least one dose. This means we are vaccinating about 0.2% of the county population each day, and this number will increase as supply increases.

Keep in mind that there are many more people eligible for vaccine than there are doses available. For example, there are 700,000 people aged 65 or older in Wisconsin, but Wisconsin is only receiving about 70,000 first time doses per week. Public Health Madison & Dane County is one of many vaccinators in Dane County, and we have administered 100% of the vaccine we have received from the state.

While this is only one model and should be interpreted carefully, it offers one perspective of what we may expect. Importantly, the article states, “Managing and reducing Rt (the infection rate) requires a sustained commitment to the public health practices and tools known to reduce the spread of COVID-19. Investment in these activities remains imperative not simply until the arrival of a vaccine but throughout the likely prolonged period during which a vaccine is being deployed.” This means we need to keep up strong prevention practices, like limiting gathering, maintaining physical distance, and wearing a mask, to keep case counts low while our community works to administer vaccine at a steadily rapid pace. But there’s reason to be hopeful.  These vaccines have been proven to minimize the impact of COVID-19, which will result in less disease and death.