An assessment of the impact of thimerosal on childhood neurodevelopmental disorders

David A. Geier; Mark R. Geier

doi:10.1080/1363849031000139315

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An assessment of the impact of thimerosal on childhood neurodevelopmental disorders

David A. Geier, Mark R. Geier

Informa (2003) • Volume 6, Issue 2, Pages 97-102

Empirical-ClinicalCrossSectionalGrade Eligible⚠️ High Risk Flags⚠️ Moderate Risk Flags

Overall Assessment

Weak Methodological Quality

Assessment created by PaperScores Medical AI v0.1.0 on Dec 14, 2025

F

10/100

Key Takeaways

•Ecological analysis of VAERS and DOE data links higher thimerosal dose to higher odds of NDDs.
•Assumes equal reactogenicity across DTaP products; provides unadjusted ORs.
•No preregistration, data sharing, or confounding control; high risk of bias.
•Claims exceedance of FDA methylmercury oral limits via instantaneous vaccine doses.
•Findings rest on passive reports and aggregate prevalence; causality not supported.

Conclusion

Methodologically weak ecological comparisons with unaddressed biases; evidence presented is insufficient to infer a causal link.

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Quality Dimensions

Bias & Integrity

COI handling, outcome switching, selective reporting

F10

Methods Rigour

Protocol clarity, sampling, controls

F10

External Validity

Generalisability, setting, population

F15

Transparency & Reproducibility

Data/code/materials availability, preregistration

F5

Significance & Novelty

Contribution vs prior art; context if known

F12

Statistical Validity

Models, assumptions, multiplicity, CI priority

F10

Integrity & Transparency

Integrity checks

P-hacking risk?

?

Serious concern

Signs of selective hypothesis testing or analysis choices that could inflate false positive rates.

Outcome switching?

?

Review recommended

Evidence that primary outcomes were changed during or after the study, potentially distorting results.

Conflict of interest?

?

Review recommended

Authors have financial or other relationships that could bias research findings.

Data integrity issues?

?

Review recommended

Concerns about the accuracy, completeness, or authenticity of the reported data.

Open science signals

Research data

?

Not shared

Raw data used in the analyses is publicly available or accessible upon request.

Analysis code

?

Not shared

Code or scripts used to analyze the data are shared for reproducibility.

Study materials

?

Not applicable

Protocols, questionnaires, and other materials are publicly available.

Premise

Primary Research Question

Does mercury from thimerosal-containing childhood vaccines contribute to neurodevelopmental disorders?

Hypothesis

Higher thimerosal-derived mercury exposure is associated with increased odds of autism and other NDDs.

Hypothesis is Falsifiable

✓Yes

Association and dose–response observable in surveillance and prevalence data.

PICO Framework

Population✓Yes

US infants/children in VAERS and DOE reports.

Intervention✓Yes

Exposure to thimerosal-containing vs thimerosal-free vaccines; mercury dose (µg).

Comparison✗No

Assumes similar reactogenicity; uses VAERS passive reports and ecological DOE baseline.

Outcome✓Yes

Autism, speech disorders, personality disorders, mental retardation.

Literature Positioning

Literature Review Balanced

Not evident

Selective citations supportive of hypothesised link; limited engagement with contrary evidence.

Evidence: pp. 97–102 refs

Research Gap Clearly Stated

Well covered

States aim to assess whether thimerosal contributed to NDD and evaluate dose–response.

Evidence: p. 97 Summary; p. 97–98 Introduction

Stated Contribution Clear

Well covered

Claims additional epidemiological evidence and analysis of instantaneous exposure vs FDA limits.

Evidence: p. 101–102 Conclusion

Study Provenance

Peer reviewed venueFunding not reportedCOI not reported8 affiliations listed

Authors & Affiliations

David A. Geier, MedCon, Inc.; Mark R. Geier, The Genetic Centers of America, Silver Spring, MD, USA.

Funding Statement

Not reported

Conflicts of Interest

Not reported

Peer Review

✓Accepted for publication: March 2003.

Evidence: p. 97 header

Methodological Assessment

Observational StudySTROBEObservational

9 applicable checklist items.

No 6 · Unclear 3

Study Design & Definitions

?

Participant Selection Described

Data source described but selection/eligibility of reports not detailed beyond database use.

Evidence: p. 98

?

Variable Definitions Clear

NDD categories described broadly; VAERS coding details not given.

Evidence: p. 98

✗

Confounding Addressed

No adjustment or control for confounding; simple ORs and linear fits.

Evidence: pp. 98–100

✗

Temporality Established

Ecological/VAERS data cannot ensure exposure precedes diagnosis at individual level.

Evidence: pp. 98–100

?

Exposure Definition Anchored

Exposure estimated from vaccine type/average mercury; weak anchoring to individual exposure.

Evidence: pp. 98–99

Bias Mitigation

✗

Selection Bias Addressed

No discussion of VAERS under-reporting/differential reporting beyond brief claims.

Evidence: pp. 98–100

✗

Misclassification Assessed

No assessment of misclassification of outcomes or exposure.

Evidence: pp. 98–100

Robustness

✗

Negative Controls or E-value

No negative controls or E-value provided.

Evidence: pp. 98–100

✗

Model Diagnostics Reported

No model diagnostics or CIs; only R2 and ORs; p-values absent.

Evidence: Figs. 1–5

Modules without applicable checklist items (9)

These designs were fully marked as not applicable but remain available for reference.

Abstract

The prevalence of autism in the US has risen from 1 in approximately 2500 in the mid-1980s to 1 in approximately 300 children in the mid-1990s. The purpose of this study was to evaluate whether mercury from thimerosal in childhood vaccines contributed to neurodevelopmental disorders. Neurodevelopmental disorder dose-response curves for increasing mercury doses of thimerosal in childhood vaccines were determined based upon examination of the Vaccine Adverse Events Reporting System (VAERS) database and the 2001 US' Department of Education Report. The instantaneous dosage of mercury children received in comparison to the Food and Drug Administration (FDA)'s maximum permissible dose for the oral ingestion of methylmercury was also determined. The dose-response curves showed increases in odds ratios of neurodevelopmental disorders from both the VAERS and US Department of Education data closely linearly correlated with increasing doses of mercury from thimerosal-containing childhood vaccines and that for overall odds ratios statistical significance was achieved. Similar slopes and linear regression coefficients for autism odds ratios in VAERS and the US Department of Education data help to mutually validate each other. Controls employed in the VAERS and US Department of Education data showed minimal biases. The evidence presented here shows that the occurrence of neurodevelopmental disorders following thimerosal-containing childhood vaccines does not appear to be coincidental.

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Study Overview

Study Design

Cross Sectional

Primary classification used to evaluate this research.

Population

US infants/children; VAERS reports post-DTaP (1997–2001) and US Dept of Education birth cohorts (1984, 1990–1994).

Brief summary of who or what was studied.

Study Arms

2 arms

Total number of intervention or comparison groups.

Pre-registration

Not registered

Indicates whether the protocol or trial was registered before data collection.

Randomisation

None reported

How participants were allocated to groups: None (no randomisation), Simple (random order), Blocked (groups balanced in blocks), Stratified (balanced within subgroups), Adaptive (allocation adjusted based on previous enrollments).

Primary Outcome

Unclear whether the primary outcome was pre-specified.

Effect Size

odds ratio: Autism OR 2.6 (VAERS)

Reviewer Notes

Ecological/cross-sectional comparisons of reported outcomes vs thimerosal exposure from passive surveillance and national prevalence data.

Publication Details

DOI

10.1080/1363849031000139315

Published

January 1, 2003

Citations

86 citations

FWCI

7.14

External Resources

DOI Link OpenAlex

Disclaimer: This assessment is generated by AI and should not be the sole basis for clinical or research decisions. Always review the original paper and consult with domain experts.