HealthDay News — The tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine given to preteens loses a large measure of effectiveness within a few years, research published in Pediatrics reveals.

To assess tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine effectiveness and duration of protection, Anna M. Acosta, MD, of the Epidemic Intelligence Service, and colleagues conducted a match case-control study during the 2012 pertussis epidemic in Washington.

Despite the state’s 86% Tdap coverage rate, 5,000 patients became ill with pertussis. Many of these patients were in their early teens. Focus was placed on about 1,700 teen patients born between 1993 and 2000 — children who would have received the newer vaccine. This group experienced 450 cases of pertussis.

Overall, Tdap effectiveness for this group was pegged at about 64%, but that plummeted to 34% two to four years post-inoculation, found the investigators. Similar findings emerged from a Wisconsin study, leading the CDC to attribute the recent spike in pertussis to a waning of Tdap effectiveness.

Going forward, CDC investigators said two things are needed: a better understanding of how exactly the pertussis bacteria works and an improved vaccine. But for the time being they don’t recommend any shift in vaccine protocols.


  1. Acosta AM et al. Pediatrics. 2015; doi: 10.1542/peds.2014-3358