Precision Vaccine Adjuvants for Older Adults: A Scoping Review

Older adults, defined as those ≥60 years of age, are a growing population vulnerable to infections including SARS-CoV-2. While immunization is a key to protecting this population, immunosenescence can impair responses to vaccines. Adjuvants can increase the immunogenicity of vaccine antigens but have not been systematically compared in older adults. We conducted a scoping review to assess the effect of adjuvants in aged populations. Adjuvants AS01, MF59, AS03 and CpG-ODN, included in licensed vaccines, are effective in older human adults. A growing menu of investigational adjuvants, such as Matrix-M and CpG plus alum, showed promising results in early phase clinical trials and preclinical studies. Most studies assessed only 1 or 2 adjuvants and no study has directly compared >3 adjuvants among older adults. Enhanced preclinical approaches enabling direct comparison of multiple adjuvants including human in vitro modeling and age-specific animal models may de-risk and accelerate vaccine development for older adults.