Effectiveness of Tdap Vaccine Drops after a Year
Waning effectiveness of a booster vaccine left adolescents in California vulnerable to pertussis, also known as whooping cough, according a study in Pediatrics.
Children receive the diphtheria, tetanus, acellular pertussis (DTaP) vaccine at ages 2, 4, 6, and 12 to 18 months and at age 4 to 6 years to protect against these three deadly diseases. Adolescents receive a routine booster dose of the tetanus, diphtheria and pertussis vaccine (Tdap) – a slightly different vaccine formulation – at age 11 or 12.
For the study, “Waning Tdap Effectiveness in Adolescents” (published online Feb. 5), researchers at Kaiser Permanente Northern California examined California pertussis outbreaks in 2010 and 2014 among adolescent members of the health maintenance organization.
Nearly all had been vaccinated with Tdap. Based on 1,207 pertussis cases, the study authors found that routine Tdap vaccination did not prevent pertussis outbreaks. Tdap provided moderate defense against the illness during the first year after vaccination but not much longer. Immunity waned during the second year, and little protection remained 2 to 3 years after vaccination.