Public health officials in California say the number of whooping cough cases has reached an epidemic level. In just the past two weeks, more than 800 people have come down with the illness that’s also known as pertussis. Two infants have died.

According to San Diego County Health and Human Services, more than 85 percent of those people who have contracted pertussis were vaccinated for the illness. That’s causing some to question the vaccine’s effectiveness.

Dr. Wilma Wooten, a public health officer for San Diego County, spoke with Los Angeles CBS radio station KNX 1070 about the outbreak. She says the pertussis vaccine offers a high level of protection during the first year after getting the full round of shots, but the protection wanes over time.

Medical experts say whooping cough outbreaks are cyclical and tend to pop up every three to five years. The last epidemic was in 2010 when more than 9,000 people were infected and 10 infants died.

That year Los Angeles public television affiliate KPBS investigated the outbreak and produced a documentary with inewsource called, “When Immunity Fails: The Whooping Cough Epidemic.” The report led to several research studies that showed pertussis vaccine immunity fades sooner than expected.

Wooten says the vaccine does lessen the severity of the symptoms, and if fewer people were vaccinated the number of cases would be even higher than what it is now.

The California Department of Public Health said in a statement there have been nearly 3,460 cases of whooping cough since January 1. That’s more than the number of cases for the entire year in 2013.

Pertussis starts with cold-like symptoms and often leads to a severe cough that can leave babies and infants gasping for air.

News, Vaccine Injury News Whooping Cough Epidemic Hits Many Vaccinated People