Our staff writer James Hamblin set out to try to understand when we’ll reach herd immunity—the point at which enough of a population has been infected to ward off more major spikes of a disease. “It turns out the number is largely up to us,” he explains.
Here are three big takeaways from his new piece on the subject:
1. Herd immunity is calculated differently for an uncontrolled virus.
In the context of vaccination, herd-immunity thresholds are relatively fixed and predictable. In the context of an ongoing pandemic, thinking of this threshold as some static concept can be dangerously misleading.
2. The threshold could be lower than once imagined.
Based on modeling, one mathematician believes it could be as low as 20 percent. Another thinks “between 35 and 45 percent” would be “a level where spreading drops drastically.”
3. But it depends on us.
The threshold can change based on how a virus spreads. The spread keeps on changing based on how we react to it at every stage, and the effects compound. Small preventive measures have big downstream effects. In other words, the herd in question determines its immunity.
One question, answered: Can I use public transit?