Central to the debate is the claim that aluminum in vaccine adjuvants is not just benign: it may be neurotoxic, immune disrupting and improperly tested.

One of the core complaints is that many vaccine trials do not use inert placebos, but instead compare the vaccine against a comparator that already contains aluminum adjuvant. In HPV vaccine trials conducted by Merck, critics say that the "placebo" often included the same or similar aluminum adjuvant (AAHS), meaning that any adverse effects of the adjuvant itself would be present in both arms—thus masking the difference. Consent forms reportedly described the placebo as inactive or saline, which critics argue is misleading when the control group actually received AAHS.

Further criticism targets amorphous aluminum hydroxyphosphate sulfate (AAHS), the proprietary adjuvant used in Gardasil vaccines. According to some research, AAHS has not been adequately evaluated for safety before widespread use. Some regulatory trial documents, especially in Europe, appear to show discrepancies—e.g. authorization of different adjuvant substances than those claimed, unclear reporting of exactly what was given to trial participants. Opponents argue these gaps make true assessment of risks impossible and that informed consent was compromised.

Aluminum as neurotoxin: Hidden risks beyond mild reactions

Critics also highlight that aluminum is known experimentally to be a neurotoxin, and they argue that its mechanisms of action in vaccines—while intended to provoke stronger immune response—may provoke unintended neurological inflammation, autoimmunity or other systemic effects, especially when adjuvants are used repeatedly or in higher doses. They point to animal studies and toxicity data, as well as to case reports, to suggest that the long term burden of aluminum in the body is under recognized.

Some recent studies that find little or no harm from aluminum in vaccines have come under fire from critics. For example, a large Danish cohort study of more than 1.2 million children over 24 years, which concluded there was no association between aluminum exposure from vaccines and hundreds of chronic conditions, is accused of statistical design choices that exclude or dilute signals of harm. The lack of a substantial unvaccinated control group, the exclusion of early deaths or high exposure cases and the blending of "low exposure" with "no exposure" groups are just some of the methodological criticisms.

Ethical concerns are also raised over the adequacy of informed consent. If participants believe their control arms are receiving inert substances when in fact they are getting aluminum adjuvants, critics say they cannot make fully informed decisions. The use of aluminum in both vaccine and placebo arms is thus framed as not only scientifically misleading but also ethically suspect.