Background. To date, there is no commercially available vaccine to prevent infectious mononucleosis, a disease frequently induced by Epstein-Barr virus (EBV) infection in adolescents or adults devoid of preexisting immunity to the virus.

Methods. A total of 181 EBV-seronegative, healthy, young adult volunteers were randomized in a double-blind fashion to receive either placebo or a recombinant EBV subunit glycoprotein 350 (gp350)/aluminum hydroxide and 3-O-desacyl-4′-monophosphoryl lipid A (AS04) candidate vaccine in a 3-dose regimen.

Results. The vaccine had demonstrable efficacy (mean efficacy rate, 78.0% [95% confidence interval {CI}, 1.0%–96.0%]) in preventing the development of infectious mononucleosis induced by EBV infection, but it had no efficacy in preventing asymptomatic EBV infection. One month after receipt of the final dose of gp350 vaccine, 98.7% of subjects showed seroconversion to anti-gp350 antibodies (95% CI, 85.5%–97.9%), and they remained anti-gp350 antibody positive for >18 months. Furthermore, there were no concerns regarding the safety or reactogenicity of the gp350/AS04 vaccine.

Conclusion. These data support the clinical feasibility of using an EBV vaccine to prevent infectious mononucleosis.

Trial registration. ClinicalTrials.gov identifier: NCT00430534.