“Herd immunity” is the idea that if enough people get immunity, we’ll all be protected. But herd immunity is very rare without a vaccine. We never got it with Polio, measles or even the flu until we had vaccines. We lose herd immunity quickly when people don’t take the vaccine. As of now, the only way to slow COVID-19 is to stay distant, wear masks, and wash your hands. Sweden tried to get through the pandemic without a lockdown. They suffered much more than their neighbors.