What if vaccines don't really stop the virus from spreading?

Justin: Like you said, the vaccines are still highly effective at preventing “severe” COVID leading to hospitalization and death, but aren’t there potentially serious complications from “mild” COVID that vaccinated people could get, such as “long COVID?”

David: The short answer is yes. The longer answer is the prevalence of those outcomes is very much an open question. Many of the higher-end estimates for long-COVID outcomes (those suggesting perhaps 30 percent or even 50 percent of cases generate enduring symptoms) are from self-reported surveys. Some of the medium-size estimates (those in the 10 percent range) often don’t compare the rates of symptoms (fatigue, anxiety, brain fog) with rates among people who never got infected with SARS-CoV-2 — and the rates can be roughly comparable, in those populations, suggesting it may be a mistake to attribute that suffering, however real, to this disease in particular. Lower-end estimates fall below one percent of cases, and while that may seem trivially small, when you apply even that prevalence to the population as a whole, where likely more than 100 million Americans have gotten sick, you get a very large absolute number of people suffering. (Though it’s also the case that many of these studies don’t distinguish between relatively mild after-effects and truly life-altering ones.) As with everything in the pandemic, you can look at relative risk and come to one conclusion (kids are pretty safe, say, at least compared to the middle-aged and elderly); and you can look at the absolute numbers and come to another (more than 500 kids have already died from the disease, and perhaps as many more could this fall and winter). That’s the hard part of dealing with a “novel” disease — bad outcomes can be really rare, relatively speaking, and still do an enormous amount of damage, given how many people are susceptible.