What Placebo Did the DTaP Vaccine Use in Clinical Trials? (FDA Data)

What does the DTaP vaccine clinical trial safety data actually show? This page documents the primary sources from every pre-licensure trial used to approve DTaP vaccines in the United States.

Both Infanrix (GSK) and Daptacel (Sanofi) were tested against DTP (whole-cell pertussis) — a vaccine that was not itself licensed via a placebo trial and that has been documented in post-licensure studies to increase infant mortality. Daptacel's package insert documents a 3.9% serious adverse event rate in previously healthy infants within 30 days of vaccination.

Infanrix (GSK)

FieldValue
Licensed~1997
Trial populationNot specified in source
Control groupDTP (whole-cell pertussis vaccine)
Solicited monitoring window8 days
Unsolicited monitoring window30 days

Source: FDA-approved package insert; GSK clinical trial submissions.

Critical Control Problem

DTP — the control used to license Infanrix — was not itself licensed on a placebo-controlled trial. DTP has been documented in multiple post-licensure studies to increase infant mortality (vaccinated infants die at higher rates than unvaccinated peers in matched circumstances). See DTaP Vaccines (Post-Licensure).

In other words, the safety baseline for licensing Infanrix was a vaccine (DTP) that multiple post-licensure studies had associated with increased infant mortality.

Daptacel (Sanofi)

FieldValue
Licensed2002
Trial populationNot specified (SAE analysis covers multiple infant cohorts)
Control groupDT or DTP vaccine
Solicited monitoring window14 days
Unsolicited monitoring window6 months
SAE rate3.9% within 30 days of vaccination

Source: FDA-approved package insert: "Within 30 days following any dose of Daptacel, 3.9% subjects reported at least one serious adverse event."

SAE Dismissal Mechanism

Because there was no inert placebo group, the 3.9% SAE rate was evaluated against a DTP control group — a vaccine already shown to increase infant mortality. The 3.9% was deemed acceptable because DTP's SAE rate was similar or higher.

The standard applied was that Daptacel was deemed safe as long as its death rate did not exceed that of DTP — a vaccine already linked to increased infant mortality. The benchmark for "safe" was not an inert baseline but a product with known serious risks.

The FDA's SAE definition (for reference): Death; life-threatening; hospitalization; disability or permanent damage; congenital anomaly/birth defect; required intervention to prevent permanent impairment; other serious important medical events.

Summary Table

BrandLicensedControlSolicitedUnsolicitedSAE Rate
Infanrix (GSK)~1997DTP (whole-cell)8 days30 daysNot specified
Daptacel (Sanofi)2002DT or DTP14 days6 months3.9% in 30 days

DTP Background — The Predecessor Used as Control

The whole-cell DTP vaccine was:

DTP's documented mortality findings in post-licensure studies are detailed in DTaP Vaccines (Post-Licensure).

Schedule

DoseTiming
Dose 12 months
Dose 24 months
Dose 36 months
Dose 4 (booster)15–18 months
Dose 5 (booster)4–6 years

The adolescent/adult booster (Tdap) is given separately. See Tdap Vaccines (Pre-Licensure).

Disease Context

Diphtheria, tetanus, and pertussis are the three target diseases. Diphtheria has been functionally eradicated in the US for decades. Tetanus is environmental (soil exposure) and is not transmitted person-to-person. Pertussis (whooping cough) continues to circulate in highly vaccinated populations because the vaccine does not prevent transmission. See Herd Immunity.

See Also

DTaP Vaccines (Post-Licensure), Pre-Licensure Safety Testing, 1986 Act (National Childhood Vaccine Injury Act), Childhood Vaccine Schedule, Combination Vaccines (Pre-Licensure), Tdap Vaccines (Pre-Licensure), Herd Immunity, Financial Immunity for Vaccine Makers, GSK, Sanofi

Frequently Asked Questions

Frequently Asked Questions

Was the DTaP vaccine tested against a placebo in clinical trials?
No. Neither Infanrix (GSK) nor Daptacel (Sanofi) was tested against an inert placebo in their pre-licensure clinical trials. Both were tested against DTP — the older whole-cell pertussis vaccine — which was itself never tested against a placebo. This means there is no inert baseline establishing the background rate of adverse events for comparison.
What was the control group used in DTaP vaccine clinical trials?
Both Infanrix and Daptacel used DTP (whole-cell pertussis vaccine) as their safety control. DTP has been documented in multiple post-licensure observational studies to increase all-cause infant mortality in vaccinated children compared to unvaccinated peers in matched circumstances. In other words, the benchmark used to declare DTaP "safe" was a vaccine already associated with increased infant death.
What is the difference between DTaP and DTP vaccines?
DTP contained whole-cell pertussis bacteria and caused more frequent adverse reactions. DTaP uses acellular (partial) pertussis components and is considered less reactogenic. DTP was phased out in the United States due to safety concerns — including neurological harms documented in legal proceedings that led to the 1986 National Childhood Vaccine Injury Act — but it was still used as the safety comparator to license DTaP.
What adverse events were reported in DTaP clinical trials?
According to Daptacel's FDA-approved package insert, 3.9% of subjects experienced at least one serious adverse event within 30 days of vaccination. The FDA defines serious adverse events as death, life-threatening conditions, hospitalization, disability or permanent damage, and birth defects. Because the control group also received a vaccine (DTP) rather than a placebo, there is no inert baseline to determine how many of these events were caused by the vaccine versus occurring naturally.
Does the DTaP vaccine prevent the spread of pertussis (whooping cough)?
No. A 2013 FDA-conducted study using baboons found that vaccinated animals were protected from symptomatic pertussis but continued to carry and transmit the bacteria as asymptomatic carriers. A 2018 world expert consensus confirmed this finding, and the CDC's own website acknowledges that DTaP and Tdap vaccination does not prevent pertussis transmission.

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