BATON ROUGE — Sen. Bill Cassidy said Friday that Louisiana is undergoing its worst whooping cough outbreak since 1990 and called on the nation's vaccine-leery health secretary to promote vaccinations.

“In my state of Louisiana, we are experiencing the worst pertussis outbreak in 35 years. The outbreak has already killed two babies,” Cassidy wrote to Health Secretary Robert F. Kennedy Jr.

Cassidy is the chairman of the Senate Health, Education, Labor and Pensions Committee. He cast the deciding vote to let  Kennedy's nomination as health secretary go forward.

Cassidy noted that Kennedy had encouraged vaccines amid a measles outbreak anchored in Texas this year.

“I want to work together to stop pertussis. Your strong public support for this vaccine will save lives,” Cassidy wrote. “Families responded to your decisive leadership when you clearly promoted the MMR vaccine to stop the outbreak in West Texas. They would respond again to your call that the DTaP vaccine is the best way to protect our babies.”

Cassidy said provisional data from the Centers for Disease Control and Prevention show 368 pertussis cases in Louisiana this year. Pertussis presents itself as a cough in which sufferers have difficulty catching their breath, resulting in a "whooping" noise.