Background . Two previous trials have suggested that a herpes simplex virus (HSV) type 2 glycoprotein D (gD) vaccine combined with the adjuvants alum and 3′-O-deacylated-monophosphoryl lipid A (MPL) is well tolerated and provides protection against genital herpes disease in women with no preexisting HSV antibody.

Methods . The safety and immunogenicity of this vaccine were evaluated in a large, multicenter, double-blind, randomized, placebo-controlled trial. The effects of sex and preexisting HSV immunity were sought.

Results . When solicited symptoms that continued after the initial 4 days of observation were excluded, the incidence of unsolicited symptoms occurring during the 7 months after vaccination (the primary analysis period) was 22.1% in vaccine recipients and 21.9% in placebo recipients. Significant increases in the number of local and systemic symptoms were found in vaccine recipients within 4 days after vaccination. However, most symptoms were mild to moderate in severity and were short lived. Women reported symptoms more frequently than did men, but preexisting immunity had little effect. The vaccine induced higher titers of HSV gD antibody on enzyme-linked immunosorbent assays than did natural infection with HSV.

Conclusion . The vaccine was generally safe, well tolerated, and immunogenic.