SAN DIEGO (AP) – California is battling the worst pertussis epidemic recorded in the state in seven decades.

A total of 9,935 cases of whooping cough cases were reported to the California Department of Public Health from Jan. 1 to Nov. 26. That’s the highest number in 70 years. The cases include one infant who died.

State officials place much of the blame on a vaccine introduced in the 1990s that research has concluded doesn’t last as long as the old one.

Another study suggests that while the vaccine may keep people from getting sick, it doesn’t prevent them from spreading whooping cough. The disease is also called pertussis.

It is cyclical, peaking every three to five years as immunity from the vaccine or the disease wanes. California’s last epidemic was in 2010.

Copyright 2014 The Associated Press.