vaccines and inactivated vaccines are safer but might require adjuvants to increase their immunogenicity. In the context of SARS-CoV-2, adjuvants are important for two reasons. First, adjuvants might increase the efficacy of the vaccine, especially in subjects with impaired immunological function, such as the elderly, or in subjects with comorbidities resulting in immune dysfunctions; in these patient cohorts, SARS-CoV-2 has a high lethality rate. Second, adjuvants can reduce the amount of vaccine protein(s) required per dose, which could facilitate scaling-up vaccine production in a reduced time frame.
Beyond alum, which is in fact a nanoscale material74 that was developed in the 1920s for the tetanus and diphtheria toxoids,75 approval for a new adjuvant did not occur until 1997, with the introduction of the oil-in-water emulsion of squalene oil and polysorbate 80 and sorbitan triol