Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Contact immunity:

This text has been unreferenced on Wikipedia for a very long time. If you can't find a source, be bold and remove it!

This text is part of the article's lead section, so referencing it may be optional. Please see WP:CITELEAD for more information.

"

Contact immunity differs from herd immunity, a different type of group protection, in which risk for unimmunized individuals is reduced if they are surrounded by immunized individuals who are unlikely to contract, harbor, or transmit the disease.[citation needed]