The return of whooping cough, also known as pertussis, continues to make news. As of August 2012, more than 23,000 cases have been reported across the US, including 13 deaths.

Now, a new study suggests children who have had the complete set of five shots, may lose their protection just a few years after the final dose, leaving them at risk for the illness.

Reporting in the New England Journal of Medicine, researchers at Kaiser Permanente evaluated data from a large pertussis outbreak in California in 2010. Since the full series of whopping cough vaccines is mandatory for all school-age children in California, researchers were looking for reasons behind the outbreak.

In this study, the risk of pertussis increased by 42-percent each year after the fifth dose of the vaccine was administered. The incidence of disease was highest among children age 8 to 11.

Researchers say these findings point to the need for new vaccines that will provide long-lasting immunity.

I’m Dr. Cindy Haines of HealthDay TV, with news from today that can lead to healthy tomorrows.