Safety and Efficacy of Staphylococcus aureus Vaccine in Older Adults

Staphylococcus aureus 4-antigen (SA4Ag) and 3-antigen (SA3Ag) vaccine may safely induce rapid and robust functional immune responses in older adults, according to a study published in Vaccine.

Following an initial study of adults aged 18 to 64 years, researchers led by C Buddy Creech, Vanderbilt University School of Medicine (Nashville, TN), conducted a second study assessing the safety and immunogenicity of S aureus SA4ag and SA3Ag vaccine in older adults.

A total of 284 healthy adults between 65 and 85 years were included in the double-blind study and randomly assigned to receive a single dose of one of three formulations of SA4Ag with escalating dose levels of rP305A, SA3Ag, or placebo. To determine how effective the vaccine was, researchers measured opsonophagocytic activity (OPA) killing and fibrinogen-binding inhibition assays. Immunogenicity was also assessed using a competitive Luminex^® immunoassay (cLIA).

Overall, results of the study demonstrated that patients responded well to all antigens. A large proportion of adults vaccinated achieved predefined antibody thresholds for each antigen by day 29, with SA4Ag eliciting a dose-level response to rP305A with up to a 13-fold rise in cLIA titres. OPA assays also showed more than 50- and 20-fold rises in functional titres using S. aureus strains expressing CP5 and CP8, respectively, at day 29. However, T-cell cytokine responses were not substantially above background levels.

There were no observable increases in the number of adverse events patients experienced with any of the vaccines.

Researchers concluded that single-dose vaccination of SA4Ag and SA3Ag in healthy adults aged 65 to 85 years safely induced rapid and robust functional immune responses, supporting further development of SA4Ag for the prevention of S. aureus disease in adults up to age 85 years.—Sean McGuire