Randomized, double-blind study in healthy adults to assess the boosting effect of Vaqta or Havrix after a single dose of Havrix

A randomized, double-blind, multicenter study was conducted to investigate the boosting effect of Vaqta or Havrix in 537 healthy adults 18-53 years of age who had received a single dose of Havrix either 24 or 52 weeks earlier . Subjects were randomized in a 2 : 1 ratio to receive either Vaqta or Havr ix for their second dose of vaccine and followed for clinical reactions for 14 days after dose 2 was administered. Serum samples were collected immedi ately before dose 2 was administered and again 4 weeks later and evaluated for hepatitis A antibody (modified hepatitis A virus antibody assay). The b ooster response rate after administration of the second dose of either vacc ine was similar (86.1% for Vaqta vs. 80.1% for Havrix). The geometric mean titers were also similar: 3274 mIU/ mL (95% confidence interval [CI], 2776- 3858) for Vaqta versus 2423 mIU/ mL (95% CI, 1911-3074) for Havrix. The pro portion of subjects who reported greater than or equal to1 injection-site a dverse experiences was lower in the patients receiving Vaqta than in those receiving Havrix (36.6% vs. 59.7%; P < .001). The results of this study ind icate that a regimen of Havrix followed by Vaqta is generally well tolerate d and highly immunogenic.