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Efficacy of pertussis vaccines diminishes over time
IDSA 49th Annual Meeting
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BOSTON — The efficacy of the diphtheria and tetanus toxoids and acellular pertussis vaccine wanes as much as 40% per year after the fifth dose, according to data presented here at the IDSA 49th Annual Meeting.
“Acellular vaccines appeared to provide less protection than the whole-cell vaccines they replaced, and their effectiveness may have waned substantially over time,” Roger Baxter, MD, and colleagues from Kaiser Permanente, said.
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The data were taken from three separate case-control studies among members of Kaiser Permanente Northern California from 2006 to 2010, which is when California began experiencing a pertussis outbreak. Researchers confirmed pertussis using polymerase chain reaction and assessed the risk for a positive pertussis test in relation to days elapsed since the fifth dose of DTaP and whether the child had up-to-date vaccinations.
“The efficacy of the fifth dose of DTaP wanes by more than 40% per year,” Baxter told Infectious Diseases in Children.
He said the study data suggested that the acellular pertussis vaccines offer less protection than whole-cell vaccines, which he attributed to the mix of proteins in the acellular version of the vaccine. However, because of the reputation the whole-cell vaccines gained as potentially harmful, it is unlikely that the acellular version would ever be replaced.
The acellular vaccines could be partially at fault for the outbreak in California, but vaccination makes a difference, Baxter said. In his study, those “children who were not up-to-date were twice more likely to have their pertussis than those children who were up-to-date.”
The researchers concluded that more education is needed about vaccine refusal, and Baxter said tetanus-diphtheria-pertussis vaccine was moderately effective in boosting protection.
Disclosure: Dr. Baxter reports receiving research grants from Sanofi-Pasteur, Merck, GlaxoSmithKline, MedImmune, Novartis and Pfizer.
For more information:
- Baxter R. #LB-6. Presented at: IDSA 49th Annual Meeting; Oct. 20-23, 2011; Boston.
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