Tdap Vaccine Adverse Events — VAERS Reports

Tdap vaccine adverse events reported to VAERS — reviewing post-licensure safety surveillance data for tetanus, diphtheria, and acellular pertussis booster vaccines.

Post-licensure findings on the Tdap vaccines (Adacel and Boostrix). The most significant findings concern the 2013 FDA baboon study and 2018 world expert consensus documenting that Tdap vaccination — like infant DTaP — does not prevent pertussis transmission. This finding directly undermines the cocooning strategy: the practice of vaccinating pregnant women, parents, grandparents, and caregivers of newborns to "protect" the infant from pertussis exposure. If Tdap does not prevent transmission, cocooned adults can still infect newborns while remaining asymptomatic themselves. The CDC and the World Expert Consensus have both acknowledged this transmission failure.

2013 FDA Baboon Study

A 2013 FDA-conducted study used baboons as the animal model for pertussis vaccination. Key findings:

• Vaccinated baboons were fully protected from symptomatic pertussis
• Vaccinated baboons continued to carry and transmit pertussis — they remained infected colonizers with no visible illness
• Unvaccinated baboons developed visible symptoms when infected and were therefore identifiable as transmitters

The study did not distinguish between Tdap (adult formulation) and DTaP (infant formulation) for the carrier effect — both rely on the same acellular pertussis antigens. The mechanism applies to Tdap as it applies to DTaP: the vaccine induces antibodies that prevent symptomatic disease but does not generate mucosal immunity that would clear the bacterium from the airways.

See DTaP Vaccines (Post-Licensure) for the parallel finding for the infant vaccine.

2018 World Expert Consensus

A 2018 world consensus conference of pertussis experts confirmed the FDA baboon study findings. Acellular pertussis vaccines (DTaP and Tdap) do not prevent pertussis transmission. The consensus statement acknowledged that asymptomatic carriage and transmission in vaccinated populations is a known phenomenon.

CDC Acknowledgment

The CDC's own website acknowledges that DTaP/Tdap vaccination does not prevent pertussis transmission. The vaccine is described as protective against symptomatic disease in the vaccinated individual, not as transmission-blocking.

The Cocooning Strategy Is Undermined

The cocooning strategy is a CDC public health recommendation:

• Vaccinate pregnant women with Tdap (in the third trimester) so maternal antibodies cross the placenta and protect the infant in the first months of life
• Vaccinate parents, grandparents, siblings, and other close contacts of newborns to prevent them from transmitting pertussis to the infant

The transplacental antibody mechanism (the first part of cocooning) may have some protective effect for newborns. The contact-vaccination mechanism (the second part) is undermined by the transmission findings:

• Vaccinated parents and contacts can still become infected with pertussis
• Vaccinated parents and contacts are now asymptomatic carriers rather than visibly ill (they have no symptoms to alert them or their physicians)
• Asymptomatic carriers may be more dangerous to newborns than unvaccinated symptomatic individuals (who would be visibly ill and likely to isolate)

This means the cocooning recommendation may, on net, increase newborn pertussis exposure rather than reduce it. See Herd Immunity.

GSK "Big Bad Cough" Class Action

GSK ran an advertising campaign called "Big Bad Cough" promoting Tdap vaccination by emphasizing the danger of pertussis transmission to newborns. The campaign implied that vaccination would prevent transmission to infants — directly contradicting the documented evidence and CDC's own acknowledgment.

ICAN filed a class action lawsuit against the campaign. GSK pulled the campaign in response to the lawsuit. See GSK.

This is one of the few documented cases of post-licensure regulatory action against a vaccine manufacturer's marketing claims, achieved through private litigation rather than FDA action.

Pregnancy Tdap: Safety Data Issues

The recommendation to administer Tdap to pregnant women in the third trimester is relatively recent (added to the schedule around 2012-2013). The pre-licensure trials for Adacel and Boostrix were not designed to evaluate safety in pregnant women. Post-licensure surveillance for pregnancy outcomes following Tdap vaccination has limited methodological rigor; observational studies have generally not found severe pregnancy complications, but they have not been placebo-controlled.

CDC Autism Lawsuit Coverage

Tdap is administered to adolescents (and pregnant women), not to infants in the relevant developmental window for autism. The CDC autism lawsuit framework therefore applies less directly to Tdap. However, the prenatal Tdap exposure (via maternal vaccination) has not been studied for autism-related outcomes in offspring. See Post-Licensure Safety Monitoring.

See Also

Tdap Vaccines (Pre-Licensure), DTaP Vaccines (Post-Licensure), Herd Immunity, GSK, Post-Licensure Safety Monitoring

Frequently Asked Questions

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