Here’s how it works with a vaccine that’s 90% effective, like polio: when nearly everyone gets the shot, it’s extremely hard for the virus to spread, so the effectiveness jumps to almost 100%. That’s called herd immunity. That’s the goal. That’s always been the goal. https://twitter.com/samstein/status/1385587437699837952

Vaccinating only the most vulnerable is triage. It’s better than nothing, but it’s not the solution. One big problem is that when the virus spreads, even among the less vulnerable population, it has more opportunity to mutate into something more dangerous and deadly.

This last point, by the way, is why we should care about vaccinating other countries. When we allow COVID-19 to continue spreading anywhere, it poses a potential threat to people everywhere - vaccinated or unvaccinated.