Predicting Human Aluminium Exposure from Vaccinations Using a Physiologically-Based Toxicokinetic Model

Background/Objectives: Poorly soluble aluminium (Al) compounds have successfully been used for decades as adjuvants in vaccines enabling an effective immune response. Yet the safety of Al exposure from vaccines is consistently questioned, especially re-garding infants. Since toxicokinetic data of aluminium after vaccination in humans are not available, model-informed predictions are needed for risk assessment. Methods: Using a physiologically-based toxicokinetic model we predicted the Al ex-posure from i.m. injections of Al-adjuvanted vaccines for full-term neonates to 50-year-old adults following the recommended vaccination schedule in Germany 2025 in addition to the continuous oral background Al exposure from dietary intake. Results: During the first two years of life, moderate (max. 2 to 3-fold) but transient in-creases of Al concentrations in plasma and in the relevant target organs liver and bone due to vaccinations were predicted. Increase in brain Al content (4%) was minimal. Most importantly, in all tissues, maximum Al levels did not exceed normal levels ob-served in infants soon after birth or known from adults. In children and adults, the rise in Al concentrations in plasma and tissues due to single vaccinations was marginal. The calculated contribution of vaccinations to the Al body burden at age 50 was negli-gible. Conclusions: From a toxicokinetic perspective, the additional Al exposure in full-term infants, children and adults from vaccinations with Al-adjuvanted vaccines according to the current recommended schedules is considered safe. The model has proven a valuable tool for predictions of Al exposure from vaccinations.