Herd immunity happens when enough of the population becomes immune to an illness because they have already had the illness or have received a vaccination to prevent them from getting the illness. This makes it unlikely that the illness will spread from person to person. (Centers for Disease Control and Prevention, CDC)
Some individuals in the media have suggested herd immunity could help bring an end to COVID-19, even before a safe and widely distributed vaccine becomes possible. However, public health experts, including Dr. Fauci and the World Health Organization, have stated that trying to achieve herd immunity through natural infection (without a vaccine) is scientifically problematic and unethical because millions more Americans would have to be infected, leading to hundreds of thousands more deaths.