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.