Friday, February 26, 2016

Poor Tdap Effectiveness Against Pertussis in Adolescents/ Journal of Pediatrics

Growing numbers of yearly pertussis cases have been recorded over the past few years in the US:  more than at any time since 1959.  

Yet additional doses of the vaccine (for diptheria, tetanus and pertussis, or DTaP) have come to be recommended by CDC:

1.  Many states have added a booster dose in 7th grade
2.  3 years ago CDC recommended that women should be given a booster dose of vaccine in the middle of every pregnancy, even though the vaccine was not approved for pregnancy use. Notes the Boostrix DTaP package insert:
"Animal fertility studies have not been conducted with BOOSTRIX. There are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, BOOSTRIX should be given to a pregnant woman only if clearly needed." 
Essentially, very young babies are at serious risk from pertussis.  For most of the rest of us, the disease causes an annoying cough for about two months. So it might be reasonable, in principle, to vaccinate pregnant women to protect their neonates from the disease.  But is it reasonable to do so in the absence of animal fertility studies proving the vaccine is safe for the fetus?  That is reckless.

It became clear to anyone who looked that the pertussis vaccine wasn't working very well.  

Now, in the March issue of Pediatrics, a study from the huge Kaiser Permanente database confirms what we were seeing.
Waning Tdap Effectiveness in Adolescents
 Nicola Klein, et al.
RESULTS: On the basis of 1207 pertussis cases, Tdap VE during the first year after vaccination was 68.8% (95% confidence interval [CI] 59.7% to 75.9%), decreasing to 8.9% (95% CI –30.6% to 36.4%) by ≥4 years after vaccination. Adolescents who were more remote from Tdap were significantly more likely to test positive for pertussis than were those vaccinated more recently (HR per year 1.35, 95% CI 1.22 to 1.50).CONCLUSIONS: 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 little protection remained 2-3 years after vaccination.