There is some optimism that most people who are infected will have some temporary immunity. But if immunity is short-lived and only present in some individuals, that already uncertain 25 percent becomes even less compelling. We also still don’t know what total population percentage would be necessary to reach the herd immunity goal. It could be as high as 80 percent of the population.

Even if we had perfect knowledge of the Swedish case, there are huge risks with copying the strategy in a country like the United States. The American people are far less healthy than Swedes. They have significantly higher rates of diabetes and hypertension, two of the most-risky underlying conditions. Four out of every 10 Americans are obese. A herd immunity strategy in America would mean that many of these people would be on some form of lockdown for many more weeks, most likely months.

Moreover, the Sweden example demonstrates that a targeted herd immunity strategy doesn’t do much to protect at-risk populations either. Deaths among the elderly in Sweden have been painfully high. In a more densely populated country like the United States, and with a larger proportion of vulnerable people, the human toll of a herd immunity strategy could be devastating.