August 17, 2018

Study Claims Tdap Vaccine in Pregnancy Doesn’t Cause Autism—Is That True Given The Facts?

By Brian S. Hooker, Ph.D., P.E. and the Children’s Health Defense Team

Since 2012, Tetanus, diphtheria and pertussis (Tdap) vaccine has been recommended for pregnant women during the third trimester of each pregnancy to provide protection to the newborn despite the glaring lack of safety data. The study, Prenatal Tetanus, Diphtheria, Acellular Pertussis Vaccination and Autism Spectrum Disorder (ASD)” by Kaiser Permanente was published this week in the journal Pediatrics, the official journal of the American Academy of Pediatrics (AAP). The study touted that the Tdap vaccine during pregnancy doesn’t cause autism. Mainstream media copied the journal’s press release and wrote stories with vigor not questioning how the study was done, who paid for it nor the results.

Brian Hooker and the Children’s Health Defense team dug deeper to find the real answers for you and your loved ones in order to evaluate the vaccine’s risks and benefits during pregnancy.

Here are seven things you need to know:

  1. In general, the minimum and average follow-up times were much too low to detect autism diagnoses.  The authors use a cut-off age of 1 year based on the minimum age at which an Autism Diagnostic Observation Schedule (ADOS) test may be administered.  Instead, they should have used the average age of diagnosis within the sampling (which is most likely between 42 and 48 months of age).  Based on this, they could have missed the majority of the cases and based on their range of follow-up times (1.2 to 6.5 years) probably missed up to 50% of the cases.  
  2. The authors state that the minimum enrollment time for a child in the system was 90 days (three months).  If a child who received a diagnosis of autism did not receive it within that time period in network, they would be considered a non-autistic control.  This inherently biases the study towards the “null hypothesis” meaning that they would not see an association.
  3. The mean follow-up period for the unvaccinated group was 4.44 years as opposed to 3.85 years for the vaccinated group.  In other words, the unvaccinated group had an additional six months of follow-up.  THIS IS A FATAL FLAW OF THE STUDY.  The mean follow-up period for the unvaccinated group (if follow-up occurred from birth, which was true for the majority of patients in this study) extended BEYOND the average age of diagnosis of autism, whereas the mean follow-up period for the vaccinated group did not.  One would expect a very large influx of autism diagnoses in this six-month window, regardless of vaccination status. 
  4. The covariates do not include vaccination status of the infant/child during the follow-up period.  If the study is designed to consider prenatal vaccines, why does it not consider post-natal vaccines as well?  
  5. The covariates include the year of birth of the patient and in the final analysis, the comparison is based on “patient-year” versus autism diagnosis and not “patient” versus autism diagnosis.  This is a common error called “multicollinearity” where the age of the patient is used as a multiple in the final analysis.  This confounds the analysis as year of birth definitely correlates with ASD rates (i.e. older children are old enough to receive a diagnosis).  This flaw also nullifies the analysis
  6. The authors possess an alarming conflict of interest specifically around the Tdap vaccine (Boostrix) in pregnancy.  Three of the authors, including the lead author, Becerra-Culqui received funding directly from GSK (the manufacturer of Boostrix) for a prior study of the vaccine during pregnancy.
  7. The study was funded in its entirety by Kaiser Permanente Southern California.  This precludes the availability of the data set used for the study and thus independent verification of the results. Brian Hooker emailed Dr. Becerra-Culqui directly to request the data set. She stated that it was not available.
The mean follow-up period for the unvaccinated group was 4.44 years as opposed to 3.85 years for the vaccinated group.  In other words, the unvaccinated group had an additional six months of follow-up.  THIS IS A FATAL FLAW OF THE STUDY.

There are two DTaP products used during pregnancy Adacel and Boostrix.  According to the manufacturer’s package insert for each, safety and effectiveness have not been established in pregnancy women:

  • Adacel   Safety and effectiveness of Adacel vaccine have not been established in pregnant women. Pregnancy Surveillance Registry: contact Sanofi Pasteur Inc. at 1-800-822-2463 (1-800-VACCINE). 
  • Boostrix Safety and effectiveness of BOOSTRIX have not been established in pregnant women. Register women who receive BOOSTRIX while pregnant in the pregnancy registry by calling 1-888-452-9622. 

Mainstream media missed the ball on this study. Perhaps they should examine the motivation behind studies like this and call into question scientific articles where conflicts are so blatantly inherent. When they fail to do their jobs and ask the right questions, consumers lose. Note that in a pull-out section, “What This Study Adds,” the journal states: “No study to our knowledge has been published examining the risk of ASD after prenatal exposure to the Tdap vaccine.” CHD believes that this is a startling admission pointing to our poor vaccine safety program in America and wonders given the clear links of Maternal Immune Activation (MIA) and autism why there wasn’t a study done BEFORE the recommendation to begin giving this vaccine to pregnant women?

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