By Sandra Yin
May 19, 2011 (Baltimore, Maryland) — The protective power of the diphtheria, tetanus, acellular pertussis vaccination (DTaP) wanes with time, according to a study presented here at the National Foundation for Infectious Diseases 14th Annual Conference on Vaccine Research.
“The most surprising finding is that the vaccine wanes as much as it does over time,” lead author Roger Baxter, MD, told Medscape Medical News. He is codirector of Kaiser Permanente’s Vaccine Study Center in Oakland, California, where he helps track and monitor the safety of vaccines for the US Centers for Disease Control and Prevention in Atlanta, Georgia.
Each year that elapses after vaccination is associated with a 36% increased risk of acquiring pertussis, he said.
“If you look over time, this means that whatever your DTaP vaccine was worth to begin with, at 3 years it’s 32% and at 5 years it’s 16% of your initial effectiveness,” Dr. Baxter told meeting attendees.
The study, which is based on a population of 22,700 Kaiser Permanente of Northern California members, 4 to 11 years of age, was conducted between December 2005 and December 2010. Researchers analyzed pertussis rates, confirmed with polymerase chain reaction (PCR), and assessed the risk for a positive pertussis test in relation to days elapsed since the fifth dose of DTaP. In 2010, California saw its highest rate of pertussis in more than 50 years.
This study was funded internally by the Kaiser Permanente Vaccine Study Center. Dr. Baxter reports receiving research grants from GSK and Sanofi Pasteur. Dr. Levine reports serving as an advisor or consultant for Merck, Aus Bio Ltd, Avant Immunotherapeutics, Medicago, Variation Biotechnologies, Alpha Vax, and Crucell Holland BV; receiving grants for clinical research from Merck; and holding a patent for and/or receiving royalties from an Aventis product.