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.
Color curves represent the minimum identification level of silent infections among children required to suppress the overall attack rate to less than 5%, with different vaccination coverage of adults and time delays for identification after infection.
