SA4Ag is a new Staphylococcus aureus 4-antigen vaccine that consists of capsular polysaccharide serotypes 5 and 8 (CP5 and CP8) conjugated to CRM197, recombinant protein clumping factor A (rmClfA), and recombinant manganese transporter protein C. (MntC). SA4Ag’s safety, tolerability, and immunogenicity were assessed in Japanese people aged 20 to 64 and 65 to 85. A total of 136 healthy Japanese people (68 per age group) were given a single dosage of SA4Ag or a placebo intramuscularly (Day 1). Reactogenicity and adverse occurrences were included in the safety evaluations. Using five distinct antigen-specific tests, the vaccine’s capacity to generate immune responses that are regarded functional owing to their ability to assist the death of S. aureus or neutralize S. aureus virulence pathways was examined. 

In all age groups, SA4Ag was well accepted, with no safety concerns. On Day 29, more than 85% of SA4Ag recipients in each age group met specific antigen limits. The geometric mean-fold rises in antibody geometric mean-folds from baseline to Day 29 in SA4Ag groups were greater than 80 and greater than 30 for CP5 and CP8 (opsonophagocytic activity assays), greater than 10 for ClfA (fibrinogen-binding inhibition assay), and greater than 15 and greater than 7 for ClfA and MntC (competitive Luminex® immunoassay), respectively. Through Month 12, antibody titers reduced, but they remained considerably above baseline and placebo levels.

In all age groups, SA4Ag exhibited an acceptable safety profile and elicited quick and substantial functional immune responses. These findings support the continued development of SA4Ag in Japan, North America, and Europe for the prevention of invasive S. aureus illness in elective surgical patients.