Pertussis epidemic sheds light on vaccine effectiveness

The 2010 pertussis epidemic in California gave federal researchers a valuable opportunity to study new ways to combat the potentially deadly respiratory illness.

A team from the U.S. Centers for Disease Control and Prevention, led by Dr. Lara Misegades, studied the effectiveness of the childhood pertussis vaccine, called DTaP, according to

Children can receive the vaccine in five doses between two months of age and four to six years of age. Officials estimate that the vaccine is effective approximately 85 percent of the time until age 11, when a booster shot is recommended. Last year, however, many seven to 10 year olds still contracted the illness despite being fully vaccinated.

Preliminary studies have raised questions as to whether the vaccine booster shot should be administered well before age 11. The CDC’s study is not expected to be finished until January 2012.

According to Misegades, DTaP was effective at a rate of 90 percent around the time a child finished the first five-shot series, but that effectiveness dropped steadily to only 70 percent within five years in most recipients.

It remains unclear whether the CDC will recommend that children receive the booster, called TDaP, before age 11. It is feared that giving TDaP to younger children would mean two trips to the doctor and lower the number of children who receive all of the immunizations recommended for 11 to 12 year olds, including the human papillomavirus vaccine and the meningococcal conjugate vaccine, reports.

A second CDC study examined a new blood test for pertussis that works within two to 12 weeks of the onset of symptoms. If the test is accurate, it could be valuable in reducing the disease’s spread. Current tests are accurate within the first week of onset only, although pertussis remains contagious in a person for three weeks.