Safe for whom? At what rate? Compared to what? For a substance injected into virtually every infant, the default is no until safety is demonstrated. Zero placebo-controlled trials in children. The two in adults both found harm. Three animal studies found brain aluminium where the models said it would not be. The most comprehensive review does not cite any of them.

When injected aluminium adjuvant forms granulomas, the aluminium stays put. When it doesn't, macrophages carry it to the brain. A controlled experiment in mice found 50 times more brain aluminium at the lowest dose than at higher doses. The question is not whether more is worse than less, but how much escapes the injection site.

No safety signal in surveillance, so no new studies needed. No study exists, so no signal found. Each step is rational. Together they form a loop that cannot generate the evidence it would need to close the question.

The global regulatory case for aluminium adjuvant safety traces to a pharmacokinetic model built on one study of 2 rabbits per adjuvant type, observed for 28 days, with lost bone samples and one lost brain. The three brains they did measure all contained aluminium. That study has never been replicated.

A 2022 systematic review found 102 trials studying aluminium adjuvants. Only 2 compared aluminium alone against an inert placebo. Together they enrolled 84 subjects.