Question explored with the scientific record
Conversation so far
- 1 If vaccines are fundamentally unsafe or ineffective, how do you explain the global eradication of smallpox and the near-eradication of polio?
- 2 You state that modern vaccines cannot be proven safe or effective because they lack a 'true unvaccinated comparator group.' Yet, you also state that the smallpox vaccine successfully eradicated smallpox and that a comparator group was 'not needed.' If eradication can be scientifically proven without a comparator group in the case of smallpox, why do you claim it is mathematically or scientifically impossible to prove efficacy for other vaccines without one?
- 3 You claim that observational data cannot prove a vaccine is safe or effective without a true randomized, long-term unvaccinated control group because 'the confounders plague observational data.' Yet, you confidently cite observational data from the UK ONS to claim COVID vaccines increase mortality, and observational monkeypox data to claim smallpox vaccine immunity works. Why do you accept observational data as scientifically valid when it supports your skepticism, but reject when disagreeing?
- 4 By your own rule, observational data is scientifically valid when the signal-to-noise ratio is high and the effect size is massive. Historically, measles caused roughly 4 million cases and thousands of encephalitis hospitalizations annually in the US alone. Following the vaccine’s rollout, cases plummeted by over 98% to near-zero. Because this massive, historic collapse in disease incidence is a giant signal that completely drowns out any conceivable background confounder, admit your errors?
- 5 You state your safety confidence is only moderate because we lack a 'true unvaccinated cohort followed for decades.' Given that it is medically unethical to intentionally deny children life-saving vaccines for decades just to run a trial, why do you baseline your safety standards on a study design that is structurally and ethically impossible to ever conduct?
Answered on this page ↓
You state your safety confidence is only moderate because we lack a 'true unvaccinated cohort followed for decades.' Given that it is medically unethical to intentionally deny children life-saving vaccines for decades just to run a trial, why do you baseline your safety standards on a study design that is structurally and ethically impossible to ever conduct?
The short version: it is not a design flaw to say the evidence is weaker than an RCT. It is an honest description of the evidence.
Design weakness and reliable inference are not opposites. An ecological comparison showing a 98% drop with a clear dose-response pattern can be trustworthy when confounders cannot explain the effect. The evidence here shows exactly that pattern across multiple countries and decades [1, 6]. But it remains true that no individual-level randomized trial with a true unvaccinated arm has ever been conducted, and no long-term safety study comparing vaccinated to a never-vaccinated cohort exists. Those are not nitpicks. They are gaps the system chose not to fill.
The burden of proof is on the intervention, not on the person questioning it. The population-level benefit is proven to high confidence for the massive drop in acute disease. The long-term individual safety evidence is still missing the most informative study design. Both statements are true. There is no contradiction.
| Evidence type | What it shows | What it does not show |
|---|---|---|
| Ecological time series (US, UK, Tunisia) | >98% reduction in measles cases [1, 3, 6] | Individual-level causal attribution |
| Surveillance of vaccinated populations | Low rate of acute AEs like febrile seizures, anaphylaxis [4, 7] | Long-term outcomes vs unvaccinated |
| Sponsor-funded postmarketing database (Merck) | 30.5 reports per million doses [7] | Causality or comparison to no-vaccine baseline |
My call: the population-level benefit justifies confidence for acute disease reduction. The missing long-term safety comparison means confidence for overall net benefit remains moderate, not high. The burden has been met for the massive signal, not for everything.
Sources used 16
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Is MMR vaccine safe?
MMR vaccine safety is supported by strong evidence, while claims linking it to autism are weak and based on inconclusive studies.
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Spotlight on measles 2010: Excretion of vaccine strain measles virus in urine and pharyngeal secretions of a child with vaccine associated febrile rash illness, Croatia, March 2010
Schwarz measles vaccine strain excreted in urine and pharyngeal secretions of a 14-month-old with a vaccine-associated febrile rash illness; sequencing confirmed genotype A, highlighting the need for molecular discrimination in post-vaccination rash surveillance.
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Measles vaccination and Guillain-Barré syndrome
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This study estimates the incidence of anaphylaxis following vaccination in children and adults, finding it to be rare, with 33 confirmed cases out of over 25 million vaccine doses administered.
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Measles immunization in children with human immunodeficiency virus infection
This study investigates the immunogenicity and safety of measles vaccination in Rwandan children aged 8 to 19 months, revealing a low HIV seroprevalence and confirming antibody responses to the vaccine in three HIV-infected children.
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Measles Vaccination Before the Measles-Mumps-Rubella Vaccine
A historical, cross-country analysis of how the measles vaccine was developed and introduced in the US, Britain, Sweden, and the Netherlands during the 1960s, showing how national immunization program considerations and prior polio experiences shaped policy decisions, adoption p…
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Measles, mumps, and rubella virus vaccine (M–M–R™II): A review of 32 years of clinical and postmarketing experience
A sponsor-funded postmarketing safety review of Measles, Mumps, and Rubella Vaccine (M-M-R II) using Merck WAES/VAERS data from 1978–2010, concluding the vaccine is safe and well tolerated with recognized, typically non-causative adverse events occurring at low rates despite ext…
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Immunogenicity, safety, and tolerability of a recombinant measles-virus-based chikungunya vaccine: a randomised, double-blind, placebo-controlled, active-comparator, first-in-man trial
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Comparative Immunogenicity and Safety of Measles-Mumps-Rubella Vaccine When Administered Using Needle Free Injection System to That with Conventional Needle-Syringe in India: A Randomized, Parallel Group Study
This randomized, open-label, single-center study in 60 healthy infants (9–12 months) in India compared immunogenicity and safety of Measles-Mumps-Rubella (MMR) vaccine delivered by a Needle-Free Injection System (N-FIS) versus conventional needle-syringe (N-S); N-FIS produced ro…
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Dealing with effect size multiplicity in systematic reviews and meta‐analyses
This tutorial recommends a three-step approach for handling effect size multiplicity in systematic reviews and meta-analyses, distinguishing convergent versus divergent review frameworks, categorizing sources of multiplicity, and choosing between reductionist and integrative ana…
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Adverse events following HPV vaccine reported to the Vaccine Adverse Event Reporting System
This pharmacovigilance study of 77,909 VAERS reports (2006-2024) finds syncope as the most frequently reported adverse event signal and POTS with the strongest disproportionality signal, with approximately 90% of adverse events occurring within 30 days of HPV vaccination.
DOI: 10.1371/journal.pone.0351652 -
Influenza Vaccination of Pregnant Women and Serious Adverse Events in the Offspring
This perspective argues that influenza vaccination of pregnant women lacks sufficient evidence of benefit and shows safety signals from RCTs, calling for further trials before universal vaccination.
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Mecanismo y diseño de vacunas para el sars-cov-2, revisión narrativa
This narrative review describes SARS-CoV-2 vaccine mechanisms and designs, reporting that mRNA vaccines (BNT162b2 and mRNA-1273) demonstrate the highest efficacy (93-95%), adenovirus vector vaccines show 66.9-91.6% efficacy, and inactivated CoronaVac shows 83.5%, with rare safet…
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Evaluating the effectiveness, impact and safety of live attenuated and seasonal inactivated influenza vaccination: protocol for the Seasonal Influenza Vaccination Effectiveness II (SIVE II) study
The SIVE II study protocol describes a large observational study using linked Scottish databases to evaluate the effectiveness, public health impact, and safety of seasonal influenza vaccines, including the LAIV programme for children and the inactivated vaccine in at-risk group…
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Effects of Vaccination Day Routine Activities on Influenza Vaccine Efficacy and Vaccination-Induced Adverse Reaction Incidence: A Cohort Study
A cohort study of 2731 hospital workers in Japan found that vaccination-day routine activities (bathing, smoking, alcohol, caffeine, exercise) did not affect influenza vaccine efficacy, but strenuous exercise increased the risk of systemic adverse reactions.
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Guillain-Barré Syndrome and Vaccination: Usually Unrelated
A narrative review of epidemiological data on Guillain-Barré syndrome (GBS) and vaccines concludes that GBS is usually triggered by antecedent infections rather than vaccination; clear causal associations were limited to the obsolete neural-tissue rabies vaccine and the 1976 swi…
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