Aluminum salts are the adjuvants of reference for toxoid vaccines. They are necessary to trigger strong, long-lasting immunization. However, these adjuvants are not broken down in the human body and leave permanent deposits: internal tattoos.
The fear is that these deposits could be associated with undesirable side effects, which has led to significant mistrust of vaccines and the risk of a regression in vaccination coverage.
Despite intensive research, the alternatives that have been developed still do not present a risk-benefit ratio as advantageous as that of the aluminum adjuvants.