FROM PEDIATRICS
A sixth dose of Tdap is initially effective in preventing pertussis in teens, but its effectiveness declines by half within 4 years after the booster, a recent study found.
“This waning is likely contributing to the increase in pertussis among adolescents,” reported Dr. Anna M. Acosta of the Centers for Disease Control and Prevention, Atlanta, and her associates ( Pediatrics 2015 [doi: 10.1542/peds.2014-3358] ).
“Advances in our understanding of the immunology and bacteriology of Bordetella pertussis are essential to optimize future prevention and control measures,” they wrote. “However, novel pertussis vaccines that effectively limit infection and transmission are also likely needed to reduce the burden of pertussis disease in the United States.”
The researchers matched three controls by birth year and primary provider practice (total 2,322 controls) to each of 836 cases of pertussis in seven counties of Washington during the 2012 pertussis epidemic. Cases were more likely than were controls to be non-Hispanic and white, but there was a lack of race/ethnicity data.
Receipt of the five childhood series doses was similar among cases (74%) and controls (75%), but a smaller proportion of both (60% cases, 58% controls) were on schedule. Among more than 84% of participants who received Tdap between ages 11 and 12, 81% of the cases and 90% of the controls received the sixth dose.
Among the 450 cases and 1,246 controls who received all acellular vaccines for the primary series, Tdap effectiveness was 63.9% overall. Stratified by time since Tdap vaccination, however, it was 73.1% within 12 months, 54.9% within 12-23 months, and 34.2% within 24-47 months.
Those born from 1999 to 2000 were presumed to have received the DTaP in infancy, and those born from 1993 to 1997 were presumed to have received a mixture of the acellular and whole-cell (DTwP) vaccines. Among those with vaccine lot numbers recorded, all vaccines administered after 1998 were acellular. A direct comparison of Tdap effectiveness between those vaccinated with the acellular primary series and those vaccinated with a mixed primary series was not possible because of time differences in vaccination between the two groups.
The research did not receive external funding, and the authors reported no relevant financial disclosures.
