Herd immunity is when enough people in a community are immune to a virus — through natural infection (catching COVID-19), vaccination, or both — that it becomes difficult for the virus to continue spreading. In this way, herd immunity protects everyone, especially those who are more vulnerable or cannot be vaccinated.
The US is making progress towards herd immunity, but we can’t be sure yet if it will be possible to achieve complete herd immunity. We already know about COVID variants, like Delta and Omicron, and we are still learning about how long immunity lasts after natural infection. But we do know that the protection provided by the COVID vaccines is slowing transmission of the virus, and helping us to live more normally, even without full herd immunity.
SOURCE: https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/herd-immunity-and-coronavirus/art-20486808 (Mayo Clinic)