Fig 2. Natural herd immunity is an appropriate or efficacious COVID-19 control strategy/natural herd immunity is working or being achieved (US).
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.