Efficacy of a 4-Antigen Staphylococcus aureus Vaccine in Spinal Surgery: The STRIVE Randomized Clinical Trial

BACKGROUND

Staphylococcus aureus is a global pathogen frequently responsible for healthcare-associated infections, including surgical site infections (SSIs). Current infection prevention and control approaches may be limited, with S aureus antibiotic resistance remaining problematic. Thus, a vaccine to prevent or reduce S aureus infection is critically needed. This study evaluated efficacy and safety of an investigational 4-antigen S aureus vaccine (SA4Ag) in adults undergoing elective open posterior spinal fusion procedures with multilevel instrumentation.

METHODS

In this multicenter, site-level, randomized, double-blind trial, subjects 18-85 years old received a single dose of SA4Ag or placebo 10-60 days before surgery. SA4Ag efficacy in preventing postoperative S aureus bloodstream infection and/or deep incisional or organ/space SSI was the primary endpoint. Safety evaluations included local reactions, systemic events, and adverse events (AEs). Immunogenicity and colonization were assessed.

RESULTS

Study enrollment was halted when a prespecified interim efficacy analysis met predefined futility criteria. SA4Ag showed no efficacy (0.0%) in preventing postoperative S aureus infection (14 cases in each group through postoperative Day 90), despite inducing robust functional immune responses to each antigen compared with placebo. Colonization rates across groups were similar through postoperative Day 180. Local reactions and systemic events were mostly mild or moderate in severity, with AEs reported at similar frequencies across groups.

CONCLUSIONS

In patients undergoing elective spinal fusion surgical procedures, SA4Ag was safe, well tolerated, but despite eliciting substantial antibody responses that blocked key S aureus virulence mechanisms, was not efficacious in preventing S aureus infection. ClinicalTrials.gov: NCT02388165.

Persistence of Immune Responses Through 36 Months in Healthy Adults After Vaccination With a Novel Staphylococcus aureus 4-Antigen Vaccine (SA4Ag)

Background

Staphylococcus aureus causes serious health care- and community-associated disease, requiring improved preventive measures such as vaccines. The investigational S. aureus 4-antigen vaccine (SA4Ag), comprising capsular polysaccharide serotypes 5 and 8 (CP5 and CP8) conjugated to CRM₁₉₇, recombinant mutant clumping factor A (rmClfA), and recombinant manganese transporter protein C (rP305A or rMntC), was well tolerated, inducing robust functional immune responses to all 4 antigens through 12 months postvaccination. This is a serological extension study through 36 months postvaccination.

Methods

In 2 previous studies, healthy adults received SA4Ag, SA3Ag (without rMntC), or placebo; serology was also assessed at ~24 and ~36 months postvaccination. Functional immune responses (antibody responses that facilitate killing of S. aureus or neutralize S. aureus virulence mechanisms) were assessed with opsonophagocytic activity killing assays (CP5 or CP8) and a fibrinogen-binding inhibition assay (ClfA). A competitive Luminex immunoassay assessed ClfA and rMntC responses. Adverse events within 48 hours of blood draw were recorded.

Results

Four hundred forty subjects (18-64 years old, 255; 65-85 years old, 185) were enrolled. At 24 and 36 months postvaccination, subjects receiving SA4Ag had substantially higher geometric mean titers (GMTs) for CP5, CP8, and ClfA vs baseline; geometric mean fold rises (GMFRs) from baseline to month 36 were 2.7-8.1. For rMntC, 36-month GMTs declined from peak levels but remained above baseline for all SA4Ag groups; GMFRs from baseline to month 36 were 1.8 and 1.5 in the younger and older cohorts, respectively.

Conclusions

Persistent functional immune responses to S. aureus antigens were observed through 36 months in healthy adults.

ClinicalTrialsgov

NCT01643941 and NCT01364571.