Counties with higher vaccination rates had lower mortality during Delta and Omicron.

Our findings were not just focused on Covid-19-deaths, but deaths from all causes.

Yesterday, my colleagues and I published a brief “research letter” in the Journal of the American Medical Association (JAMA). My hospital asked me to do a Q&A to describe what we found. The upshot is that counties in Massachusetts with higher vaccination rates fared far better during both Delta and Omicron than ones with lower vaccination rates—not just in terms of Covid-19 mortality, but all mortality.

Today’s Inside Medicine is that Q&A. If you have your own questions, ask away!

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What “Excess Mortality” Rates Reveal about the Impact of COVID.

(via LinkedIn)

How do you measure the burden of mortality from the COVID-19 pandemic? Researchers led by Jeremy Faust, MD, of the Brigham’s Department of Emergency Medicine, are investigating clues from excess deaths—the difference between the observed numbers of deaths in a specific period compared to expected numbers of deaths in the same period. Faust and colleagues published a paper in JAMA in May that reported on excess deaths in Massachusetts during Omicron and Delta waves of COVID-19, and this week, they have published a letter in JAMA with updated data showing that counties in Massachusetts with higher vaccination rates fared much better than counties with lower rates. Faust answered questions about the latest data and about excess mortality rates more broadly.

Q: What is the concept behind “excess mortality” and what kind of insights can it provide?

JF: Excess mortality is the number of deaths from all causes (not just COVID-19) that happen in a time period that exceed normal expected numbers.  For more than a century, governments have been keeping excellent records on how many people die each week or month. So, we know with a lot of confidence what the normal ranges are for any given time. When COVID hit, we were well above normal, unlike anything we’d seen since 1918. As the pandemic goes on, we have seen it rise and fall. 

One advantage of tracking excess mortality is that it does not rely on the cause of death for any person, which can be pretty subjective. If someone dies of COVID-19 but they were in hospice for advanced cancer, it would be hard to make the argument that COVID-19 was “the cause” of death. It might have hastened it. With excess mortality, all deaths count, and we just want to know “are more people dying than ought to be.” Throughout the pandemic, excess mortality has very tightly tracked with COVID-19 deaths, which gives us important information—that COVID itself is behind these changes.  

Q: How did you become interested in this area of research? Have you been surprised by what you’ve learned from studying these rates?

JF: I became interested in this because early in the pandemic, I wanted to know how out-of-the-ordinary things really were. But doctors are human and with COVID being on the news, I wondered whether they’d be more likely to list COVID as a cause of death, and that maybe some of these deaths would have happened anyway. Excess mortality proved to me without a doubt that this was not the case—we truly were seeing extraordinarily high mortality rates. What we were seeing on the ground matched up with the “big data” we could get from the state. I’ll never forget the first time I saw the data for Massachusetts for the weeks of mid-April 2020. It was like a punch in the gut. We were having 2,500 people dying per week, whereas normal would have been 1,100 or so. It was a catastrophe, and excess mortality made that point very clearly. After that, I assembled the team that studies excess mortality now and we’ve put out a number of papers that I think capture the historical nature of this crisis. Overall, what has surprised me is two things. First, the magnitude of excess mortality in those early days and then again during Omicron. Second, that it’s lasted this long. We still are recording more deaths than we “should” be. This spring was far better, normal in fact. But we’re now back to having 8-10% more deaths than we should be in the state. 

Q: What new data do you include in this letter and what do these data help illustrate?

JF: In this research letter, we show that in Massachusetts there has been an impressive inverse relationship between excess mortality and vaccination rates at the county level. That is, the more vaccinated a county is, the fewer excess deaths there have been. It’s one way of showing how effective and important the vaccines have been, both before and during the Omicron waves. 

Q: What’s the key message here for the public? What do you hope people will take away from reading about your research on rates of excess mortality?

JF: The key message is that vaccination rates are correlated with much better outcomes (i.e., fewer excess deaths), and that we can see this at the county level, even in a place like Massachusetts where vaccination rates are quite high. Everyone needs to be vaccinated, and particularly people with underlying conditions need to stay up-to-date on boosters.