evidence: Efficacy. The efficacy of HAVRIX was evaluated in a double-blind, controlled, randomized clinical trial conducted in Thailand among approximately 40,000 children aged 1--16 years living in villages that had high rates of hepatitis A (117). After 2 doses of vaccine (360 EL.U. per dose) administered 1 month apart, the efficacy of vaccine in protecting against clinical hepatitis A was 94% (95% confidence interval [CI] = 79%--99%). A double-blind, placebo-controlled, randomized clinical trial using VAQTA was conducted among approximately 1,000 children aged 2--16 years living in a New York community that had a high rate of hepatitis A (118). The protective efficacy against clinical hepatitis A was 100% (lower bound of the 95% CI = 87%) after administration of 1 dose (25 U) of vaccine. [...] Approximately 10,000 persons were administered VAQTA in prelicensure clinical studies, and no serious adverse events were reported among participants (192). Among adults, the most frequent side effects that occurred <5 days after vaccination included tenderness (53%), pain (51%), and warmth (17%) at the injection site and headache (16%). Among children, the most common side effects reported were pain (19%), tenderness (17%), and warmth (9%) at the injection site. In one placebo-controlled trial among children, adverse reactions among vaccine recipients did not differ substantially from those that occurred among persons who received placebo (118).