Study: Vaccination against whooping cough fades in pre-teens

Children immunized against whooping cough between the ages of eight and 12 were found to be more likely to catch the disease than children of other ages during a 2010 California outbreak in a recent study.

The results of the study, conducted at Kaiser Permanente Medical Center in San Rafael, California, suggest that the childhood vaccine wears off as children get older. Whooping cough, which is also known as pertussis, is caused by the Bordetella pertussis bacterium. The infection includes symptoms such as an intense cough lasting weeks that can cause pneumonia, an inability to breathe or death, Reuters reports.

"We have a real belief that the durability (of the vaccine) is not what was imagined," David Witt, an infectious disease specialist at Kaiser Permanente, said, according to Reuters.

The pertussis vaccine is a five shot series called DTaP and is recommended for kids at ages two-, four-, six- and 18-months of age, as well as at four to six years of age. The Centers for Disease Control and Prevention recommends that children receive a Tdap booster shot at age 11 or 12. The California outbreak in 2010 was the largest seen in the state in more than 50 years.

"We started dissecting the data," Witt said, according to Reuters. "What was very surprising was the majority of cases were in fully vaccinated children. That's what started catching our attention. The longer you went from your last vaccine, the greater your risk of disease."

The study found that the vaccine was effective approximately half of the time for all children, but just 24 percent of the time in children between the ages of eight to 12 years old.

"For pertussis, having even 24 percent helps (mitigate an epidemic), but you'd sure like it higher than that," Witt said, according to Reuters.