Whooping Cough Vaccine May Not Give Long-Term Protection Sept. 20, 2011 (Chicago) -- The protection provided by the vaccine against whooping cough may wane after only about three years, a preliminary study suggests.

The findings come from a survey of about 15,000 children in Marin County, Calif., where an outbreak of the highly contagious bacterial disease killed 11 infants and sickened about 9,100 people in 2010.

In 2006, there were only about 13,300 new whooping cough cases in the entire country, according to the CDC.

"The attack rate is the highest in California in 50 years," says researcher David Witt, MD, chief of infectious diseases at Kaiser Permanente Medical Center in San Rafael, Calif.

The bulk of the cases occurred among "fully vaccinated children" aged 8 to 12, he tells WebMD.

"That was a surprise to us," as it was thought most cases would be among unvaccinated children, Witt says.

The childhood vaccine schedule for whooping cough calls for shots at ages 2 months, 4 months, and 6 months; 15-18 months; 4-6 years; and 11-12 years.

Whooping Cough: Is Your Child Protected?