Fig. 4: A new framework for development of adjuvants.

a | The current model of developing vaccines containing novel adjuvants represents a linear progression from the systematic testing of novel candidates in mice, to the advancement of promising candidates to testing in non-human primates (NHPs), and the eventual testing in humans in multiple phases of clinical trials. b | The new model we propose relies on a process of iterative testing in mice, organoid cultures, NHPs and humans. We advise the early use of small-scale experimental human trials and the use of systems biology approaches to generate multiparametric immunological read-outs, which enable the generation of novel hypothesis and adjuvant concepts that can be retested in preclinical models.