An official website of the United States government
Here's how you know
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.
Comparison of Hib ascertainment between two time periods: 1991–1994, when enhanced Hib surveillance was performed in five English regions and Wales only, and 1997–2003, when Hib surveillance was in place for the whole of England and Wales