The Advisory Committee on Immunization Practices recommends which vaccines Americans should receive. Its guidance shapes insurance coverage and school requirements nationwide. For decades, presenters have been physicians, immunologists, and public health experts.
On December 5, the committee heard from Aaron Siri. Siri is a trial attorney whose firm has received roughly $20 million since 2017 from the Informed Consent Action Network, an anti-vaccine organization. He has petitioned the FDA to revoke approval of the polio vaccine and advises HHS Secretary Robert F. Kennedy Jr.
His 76-slide presentation argued that childhood vaccines were never properly tested against placebos. He has since said that no one has identified errors in his claims.
Here are several.
The Trick
Siri is a skilled litigator, and his presentation is structured like a legal brief. He narrows the scope to one specific FDA filing, excludes hundreds of other trials, and declares victory when the artificially constrained record appears thin.
When he claims a vaccine was “never tested against a placebo,” he’s relying on a narrow legal definition: that the specific trial submitted for the current U.S. license used an active comparator rather than saline. He systematically omits foundational placebo-controlled trials that established the safety of these antigens. Trials conducted before the current product’s licensure, trials run in other countries, trials published in peer-reviewed journals but not listed in a specific FDA filing.
He’s auditing regulatory paperwork. Not science.
Regulatory submissions are administrative records for a specific commercial approval. The scientific evidence base is far larger, spanning decades of research across dozens of countries. Conflating the two is the core sleight of hand. It’s the same technique RFK Jr. uses. Both treat FDA package inserts as if they contain the sum total of vaccine safety evidence.
They do not.
What the Primary Literature Shows
Take hepatitis B. Siri claims the vaccines were licensed based on “uncontrolled trials” with safety monitored for only “4-5 days.”
In 1980, Szmuness and colleagues published results from a randomized, double-blind trial in the New England Journal of Medicine. They enrolled 1,083 subjects and randomized them to vaccine or placebo. The placebo was alum in vaccine diluent, visually indistinguishable from the vaccine. They followed participants for 24-30 months. Not days. Months. They tracked clinical hepatitis and serologic events. Side effects were 24.3% in the vaccine group versus 21.4% in the placebo group. No significant difference. Efficacy was 92%.
That’s two and a half years of follow-up in a randomized, blinded trial.
In 1984, Wong and colleagues published a randomized, double-blind, placebo-controlled trial in Hong Kong newborns. The placebo was 0.66 mg aluminum phosphate in 1 ml physiological saline. Follow-up ran 12-24 months. The authors reported “no serious side-effects” attributable to vaccination. The placebo group had a 73.2% chronic carrier rate. The vaccine reduced this to 2.9%.
The National Academies documented over 50 placebo-controlled trials of plasma-derived hepatitis B vaccine alone, involving over 100,000 participants.
So why does the package insert Siri cites show only 147 infants? Because that trial was a bridging study for a new recombinant formulation, demonstrating equivalence to vaccines already proven safe in the trials above. Siri is auditing the bridge and ignoring the foundation it connects to.
The pattern holds across the schedule.
Pneumococcal vaccines? Cutts and colleagues randomized 17,437 Gambian infants to vaccine or placebo with no pneumococcal antigens. Follow-up ran approximately two years. The vaccine showed 77% efficacy against invasive disease and a 16% reduction in all-cause mortality. Serious adverse events were actually lower in the vaccinated group: 110 versus 131.
Lucero and colleagues randomized 12,191 Filipino infants to vaccine or placebo. The placebo was 0.83% sodium chloride buffered with phosphate. Saline. This trial exists. It is indexed in PubMed. It used saline. It directly refutes the claim that pneumococcal vaccines were “never tested against saline.”
Klugman and colleagues randomized 39,836 South African infants. The incidence of serious adverse events was similar in both groups.
DTaP? Siri claims it was tested against whole-cell DTP rather than saline. This ignores the component isolation trials. To test the pertussis component, researchers compared DTaP to DT, which is diphtheria-tetanus without pertussis. Both arms received protection against diphtheria and tetanus; only the DTaP arm received pertussis protection. DT serves as the placebo for the pertussis antigen. This is how you isolate the safety signal of a single component.
Gustafsson randomized 9,829 Swedish infants. Greco randomized 15,601 Italian infants. The rates of adverse events were similar for the acellular vaccines and the DT control. Whole-cell caused significantly more fever and local reactions. We switched from whole-cell to acellular pertussis because the trials showed DTaP was safer. Comparing DTaP to DTP demonstrated that the newer vaccine was safer.
HPV? Reisinger et al randomized 1,781 children (9–15) to Gardasil or a non–aluminum-containing placebo. The placebo had the same constituents as the vaccine except HPV L1 VLPs and aluminum adjuvant. Fever rates were similar, and no serious vaccine-related adverse events were reported. This trial exists and is indexed in PubMed. It is a placebo without antigen and without aluminum, which is one class of control Siri claims does not exist. For a saline-placebo–controlled HPV trial, see Garland et al. (2015): 924 females randomized 2:1 to 9-valent HPV vaccine or saline placebo (in prior qHPV recipients). Injection-site reactions were markedly higher with vaccine (91.1% vs 43.9%), while serious adverse events were rare in both groups, with one vaccine-related SAE in each arm.
Rotavirus? Ruiz-Palacios enrolled 63,225 infants. Vesikari enrolled 68,038 infants. Serious adverse events were monitored for one year. That’s over 131,000 infants in placebo-controlled trials with extended follow-up, for one vaccine.
Polio? The Francis Field Trial in 1954 enrolled over 400,000 children. The placebo was Medium 199, cell culture fluid without virus. It remains one of the largest randomized controlled trials in medical history.
I could continue. The point is not to recite every trial ever conducted. The point is that these trials exist. They’re indexed in PubMed. They’re available to anyone willing to look.
The Neomycin Distraction
Siri highlights a 1984 varicella trial where the placebo contained neomycin, arguing this wasn’t “inert.”
The paper lists “45 mg per milliliter.” This is a typo. Modern Varivax contains trace quantities, typically under 25 micrograms. Same manufacturer, same process. The published unit is off by a factor of 1,000.
Our database classifies neomycin-containing placebos as excipient controls, not inert comparators. That was always the methodology, even though trace neomycin at these doses is clinically benign.
But Siri’s argument backfires regardless. The study used toxicological isolation: vaccine contained virus plus stabilizer plus trace neomycin, while placebo contained stabilizer plus trace neomycin. If the excipients caused harm, the placebo group would show it. They didn’t. The only significant difference was minor local reactions in the vaccine group, attributable to the live virus.
The Safety Monitoring Sleight of Hand
Siri claims safety was reviewed for only “4-5 days.”
Each trial actually has two monitoring windows. Solicited events like fever, soreness, and injection site reactions are recorded on diary cards for 4-7 days. Serious adverse events are monitored for months to years. Siri cites the diary card period and ignores the serious adverse event data in the same documents.
From the package inserts he cites: Prevnar 20 monitored serious adverse events for 6 months. Gardasil 9 monitored them for up to 4 years. RotaTeq monitored them for 1 year. The Szmuness hepatitis B trial followed participants for 30 months.
Moving the Goalposts
When shown placebo-controlled trials, Siri employs predictable tactics.
He narrows the scope, restricting “valid evidence” to only trials in FDA package inserts while excluding post-licensure studies, international trials, and the broader peer-reviewed literature. When shown inert placebos, he attacks the definitions, calling the classifications “fast and loose.”
He’s treating a scientific question like cross-examination.
He demands the impossible trifecta: a single trial must have a saline placebo, years of follow-up, and statistical power to detect rare events. He explicitly says “it needs all three.” No single trial can do all three. Power comes from large samples. Long-term safety comes from post-market surveillance. Placebo controls come from pre-licensure efficacy trials. By demanding one trial do everything, he can dismiss the entire body of evidence.
Show him a placebo trial: “But that was in Africa.” Show him one in Finland: “But that used a buffer.” Show him one with saline: “But that was only 60,000 kids.”
If the standard shifts every time evidence is provided, the goal is not safety. It’s constructing a position no evidence can satisfy.
Biology doesn’t change at borders. FDA regulations explicitly permit foreign trial data for U.S. licensure. Sample sizes in these trials (17,437, 39,836, 63,225, 68,038) are among the largest randomized controlled trials in medical history.
The Ethical Reality
Siri demands a randomized trial of fully vaccinated versus completely unvaccinated children.
To run this study, you’d randomly assign thousands of infants to receive no protection against measles, polio, or tetanus. No institutional review board would approve it. You cannot ethically assign children to a group designed to leave them vulnerable to deadly diseases.
The demand is the trick: ask for something unethical, then claim its absence proves vaccines are untested.
Once a vaccine is proven effective, it becomes the standard of care. Under the Declaration of Helsinki, new interventions must be tested against the best current proven treatment. If researchers followed Siri’s demand and gave a control group saline instead of DTaP, and a child died of whooping cough, those researchers would be guilty of gross negligence.
We don’t sacrifice children to satisfy a lawyer’s demand for “new” data.
The Evidence That Exists
Our review identified over 1,700 randomized controlled trials involving more than 10 million participants. Of these, approximately 680 used inert placebos: saline, water, or buffer without antigen.
Every antigen on the routine childhood schedule has been studied in placebo-controlled trials. The claim that the schedule is “untested” requires ignoring every single one.
The science doesn’t live in Section 6 of a package insert. It lives in Wong, Szmuness, Francis, Cutts, Klugman, Lucero, Vesikari, Gustafsson, Greco, Reisinger, and hundreds of other trials. It lives in the Vaccine Safety Datalink. It lives in the near-elimination of diseases that once killed thousands of children annually.
That evidence exists. It’s indexed in PubMed. It’s available to anyone willing to look.
“No evidence exists” is not a legitimate critique when the evidence is sitting in PubMed. The claim that “no one has identified errors” does not survive contact with the primary sources.
Update (Dec 11 2025): A prior version described the Reisinger trial comparator as “saline placebo.” The Methods specify a non–aluminum-containing placebo with the same constituents as the vaccine except HPV L1 VLPs and aluminum adjuvant—i.e., an excipient-matched control, not saline. This has been corrected. The control arm therefore excluded both antigen and aluminum adjuvant, which is the point being discussed.
Jake Scott, MD is an infectious diseases physician and clinical associate professor at Stanford School of Medicine