DTaP & TDaP Vaccines
Study: Acellular pertussis vaccines protect against disease but fail to prevent infection and transmission in a nonhuman primate model
FDA Scientists conducted a study on the acellular pertussis vaccine by infecting baboons with the virus.
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None of the vaccinated or naturally immune baboons became ill with pertussis. However the virus lingered in the throats of the baboons that were vaccinated for 35 days. The baboons that were vaccinated with the acellular pertussis vaccine were able to pass the infection onto other baboons.
Study: Waning Tdap Effectiveness in Adolescents
"Routine Tdap did not prevent pertussis outbreaks. Among adolescents who have only received DTaP vaccines in childhood, Tdap provided moderate protection against pertussis during the first year and then waned rapidly so that litle protection remained 2-3 years after vaccination." Page 1
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"We estimated that DTaP protection wanes 42% per year on average after the fifth dose at 4 to 6 years of age8 and predicted that there would be larger pertussis outbreaks as the cohort of children vaccinated exclusively with DTaP vaccines expanded and became older and more distant from their fifth DTaP dose." Page 2