SAN DIEGO (AP) — California is battling the worst whooping cough epidemic recorded in the state in seven decades.

A total of 9,935 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.

California officials partly blame the limitations of a vaccine introduced in the 1990s.

Doctors emphasize that the inoculation has led to fewer deaths than in the past, and in instances where people do get sick, their illnesses aren’t as severe.

But research has concluded the new vaccine doesn’t last as long as the old one.

The disease — also called pertussis — peaks every three to five years as immunity from the vaccine or the disease wanes.