may not have been detected through lack of statistical power in the original studies

At the 2019 World Health Organization Vaccine Safety Summit, Stephen Evans, BA, MSc, Professor of Pharmacoepidemiology at the London School of Hygiene and Tropical Medicine stated,

Adjuvants multiply the immunogenicity of the antigens that they are added to, and that is their intention. It seems to me they multiply the reactogenicity in many instances, and therefore it seems to me that it is not unexpected if they multiply the incidence of adverse reactions that are associated with the antigen but may not have been detected through lack of statistical power in the original studies.

https://form.jotform.com/200315309354143