Post-licensure vaccine safety monitoring: how the systems work, their documented limitations, and what VAERS, VSD, and other surveillance tools can and cannot tell us.
The process of monitoring vaccine safety after a vaccine has been licensed and deployed to the public. Aaron Siri argues that vaccinologists systematically avoid conducting the studies needed to identify post-licensure harms — and then use the resulting absence of evidence as proof that no harms exist.
Explanation
Once a vaccine is licensed, conducting a placebo-controlled trial is considered unethical by the medical community. This means post-licensure safety must be assessed through other methods: passive reporting systems (VAERS), epidemiological studies using health data, or prospective cohort studies. Vaccinologists, per Siri's argument, avoid funding or conducting studies that could establish causation for claimed harms — and then point to the lack of studies as proof the vaccine doesn't cause those harms.
The IOM Finding
In 2012, the IOM Vaccine Safety Report was published after the CDC and HRSA paid the IOM to review the entire body of vaccine safety literature for 158 commonly claimed vaccine harms:
Category
Number of harms
Evidence supports causation
18
Evidence rejects causation
5
Insufficient evidence to determine causation
135
135 of the 158 most commonly claimed serious vaccine injuries had never been adequately studied to determine whether vaccines cause them or not.
The Logical Trap
Siri documents that despite this IOM finding, Stanley Plotkin and his protégés tell the public that vaccines do not cause the 135 under-studied harms. This reverses the scientific burden of proof:
IOM's actual finding: "We don't know — the studies haven't been done."
Plotkin's claim: "Vaccines don't cause this harm."
Plotkin's logic when pressed: In the absence of data, his presumption is that vaccines don't cause harm.
The problem: Claiming that vaccines do not cause the 135 injuries the IOM found "insufficiently studied" — without conducting the studies — substitutes presumption for evidence.
Encephalitis example
Siri asked Plotkin: "Can the hepatitis B vaccine cause encephalitis?"
Plotkin: "No, I would say definitely not."
IOM's conclusion: "The evidence is inadequate to accept or reject a causal relationship between hepatitis B vaccine and encephalitis."
Autism example
No randomized, placebo-controlled study exists showing DTaP/Tdap does not cause autism
IOM found no studies ruling it out; found one study showing increased autism rate with pertussis vaccines (which IOM discounted)
Congress ordered HHS in 1986 to study autism/pertussis connection; by 2012 IOM confirmed no such study had been conducted
Plotkin admitted he would tell parents DTaP doesn't cause autism despite no proof: "Absolutely"
ICAN sued CDC for such studies; CDC could not produce a single qualifying study
The Gregory Poland Case
Gregory Poland's tinnitus following Covid-19 vaccination illustrates the post-licensure monitoring failure pattern:
28,000+ VAERS reports of tinnitus post-Covid vaccine
Pfizer: "No causal association has been established"
CDC: "Data from safety monitoring are not sufficient to conclude a causal relationship exists"
No study has been funded to properly assess causation
Poland himself demands mechanistic studies before accepting causation — studies no one will fund
The "Demand Mechanistic Studies" Escape Valve
To disprove causation, vaccinologists accept epidemiological evidence (which can be manipulated). To prove causation, vaccinologists demand mechanistic studies — studies establishing the precise biological pathway. No one will fund those studies. Result: causation can never be established.
The Full Post-Licensure Picture
The Three IOM Reviews and AHRQ's Vacuous Comprehensive Review
1991 IOM Review: Examined 22 claimed vaccine injuries — concluded 12 had insufficient evidence to determine causation.
1994 IOM Review: Examined 54 claimed vaccine injuries — concluded 38 had insufficient evidence.
2012 IOM Review (Adverse Effects of Vaccines: Evidence and Causality):
The IOM recommended that the CDC commission prospective cohort studies comparing health outcomes in vaccinated vs. unvaccinated children — the CDC never did this
2014 AHRQ "Comprehensive Review" of Vaccine Safety:
AHRQ reviewed 20,478 studies
Only 97 studies qualified for inclusion (children's vaccines, using accepted methodology)
Of those 97, 77 were pharma-funded
Breakdown by vaccine — studies qualifying to show the vaccine does NOT cause specific harms:
- Hep B: 0 qualifying studies
- DTaP: 0 qualifying studies
- PCV (Prevnar): 0 qualifying studies
- IPV: 0 qualifying studies
- MMR: 0 qualifying studies
- Hep A: 0 qualifying studies
- Tdap: 0 qualifying studies
- Flu (children): 0 qualifying studies
Despite this review, the CDC continues to claim these vaccines don't cause the chronic conditions listed in their package inserts
The Autism Saga: CDC Sued in Federal Court
The Chain of Unaddressed Studies:
1986 Act: Congress mandated HHS to study the pertussis vaccine-autism connection
1991 IOM: insufficient evidence for the connection
AHRQ 2014: zero qualifying studies for DTaP and autism
ICAN v. CDC (December 2019):
ICAN sued CDC in federal court demanding all studies the CDC relied on for its claim that infant vaccines (DTaP, Hep B, Hib, PCV13, IPV) do not cause autism
CDC filed a court stipulation listing 20 studies as its entire evidentiary basis
ICAN's analysis of those 20 studies:
- 15 were exclusively about MMR or thimerosal — not the infant vaccines (DTaP, Hep B, Hib, PCV, IPV) on which the claim was made
- Of the remaining 5, none showed that the specific infant vaccines do not cause autism
- Conclusion: not a single study in CDC's entire evidence base showed that the infant vaccines given in the first 6 months of life do not cause autism
Kathryn Edwards Deposition (August 2020):
Kathryn Edwards (Vanderbilt University; conducted numerous vaccine clinical trials; served on FDA and CDC committees) was deposed by ICAN under oath. Key admissions:
The vaccine clinical trials she conducted were NOT designed to determine whether a vaccine causes autism
She admitted no studies exist that were designed and powered to evaluate whether any of the infant vaccines (DTaP, Hep B, Hib, PCV, IPV) cause autism
She conceded that the CDC's claim that these vaccines don't cause autism is not supported by studies designed to answer that question
Vaccinated vs. Unvaccinated Studies
CDC's official position is that a vaccinated vs. unvaccinated (VvU) study is "not feasible" and "unethical." Siri documents that CDC published a white paper detailing how such a study could be conducted — but never funded or conducted it.
Studies that have been conducted (typically without pharma funding or CDC support):
Jackson State University Pilot Study (Anthony Mawson et al., ~2017):
Sample: 320 vaccinated children, 48 unvaccinated homeschooled children
Results in vaccinated vs. unvaccinated:
- 320% more autism
- 420% more learning disabilities
- 270% more neurodevelopmental disorders overall
Sage Open Medicine Study:
Vaccinated children vs. unvaccinated:
- 118% more developmental delay
- 349% more asthma
- 113% more ear infections
Ulster County, NY Cohort (unvaccinated children):
Cohort of deliberately unvaccinated children tracked over time
Results: 0% ASD, 0% seizures, 0% diabetes (vs. population background rates for all three)
Amish Community Study:
168 unvaccinated Amish children surveyed
Result: none diagnosed with autism, ADHD, or standard chronic childhood conditions
University of Colorado Study:
Examined multiple environmental factors correlated with autism rates
Finding: cumulative vaccine doses were among the highest-correlated factors — higher than many other studied variables
Siri's argument: these studies are small and methodologically imperfect — because no large, rigorous, properly powered study has ever been funded. The perfect is being used as the enemy of the good by the same agencies that refuse to fund a proper study.
The "Not Feasible / Unethical" Barrier
CDC and FDA respond to calls for a VvU study by arguing:
1. It would be "unethical" to leave a control group unvaccinated
2. It is "not feasible" because there aren't enough unvaccinated children
Siri's counter:
The CDC published a white paper describing how to conduct such a study
There are millions of unvaccinated children in the US (religious/medical exemptions, homeschoolers)
Retroactive cohort studies using existing unvaccinated populations are possible — and some have been conducted by researchers without CDC support
The real barrier is that pharma companies would have no incentive to fund a study that could find harm, and neither would CDC (which is institutionally committed to the vaccine program)
How does the US monitor vaccine safety after a vaccine is approved?
Post-licensure monitoring relies primarily on VAERS (a passive voluntary reporting system), the VSD (a CDC-controlled database of health records), and V-safe (a smartphone tool used only for COVID-19 vaccines). Once a vaccine is licensed, placebo-controlled trials are considered unethical. A Harvard study funded by AHRQ found "fewer than 1% of vaccine adverse events are reported" to VAERS, and the VSD restricts independent researcher access.
Has the CDC ever conducted a vaccinated vs. unvaccinated study?
No. The CDC published a white paper describing how such a study could be conducted but never funded or conducted it. The CDC argues such studies are "not feasible" and "unethical." Several independent studies — including from Jackson State University, Sage Open Medicine, and the Henry Ford Health System — have been conducted without CDC support and generally found higher chronic disease rates in vaccinated cohorts.
What did ICAN's lawsuit reveal about CDC autism studies?
ICAN sued CDC in federal court for all studies the CDC relied on to claim infant vaccines don't cause autism. CDC listed 20 studies as its entire evidence base. Analysis showed 15 were exclusively about MMR or thimerosal, not the infant vaccines (DTaP, Hep B, Hib, PCV, IPV) in question. Not a single study in CDC's evidence base showed that the infant vaccines given in the first 6 months of life do not cause autism.
What did the 2014 AHRQ comprehensive review find about vaccine safety evidence?
AHRQ reviewed 20,478 studies but only 97 qualified for inclusion. Of those, 77 were pharma-funded. Zero qualifying studies existed showing that Hep B, DTaP, PCV, IPV, MMR, Hep A, Tdap, or flu vaccines do not cause specific chronic conditions. Despite this, the CDC continues to claim these vaccines are safe and don't cause the chronic conditions listed in their own package inserts.
Why won't anyone fund studies to determine if vaccines cause specific harms?
Vaccinologists accept epidemiological evidence to disprove causation but demand mechanistic studies (precise biological pathway) to prove it — studies no one will fund. Pharma companies have no incentive to fund studies that could find harm since they have no liability. The CDC has an institutional disincentive since it defends against vaccine injury claims through the VICP. The result is that causation can never be established under the current system.
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