Hepatitis A: The Vaccine Dividend

The disease we recognize today as hepatitis A had been proven many decades ago to be transmitted by the fecal-oral route and had been classified loosely as "infectious," in contrast to "serum," hepatitis before the viral agent, hepatitis A virus (HAV), was visualized in 1973 [1]. Within half a decade, HAV had been cultivated in vitro, and a prototype vaccine was developed [2, 3]. During the early 1990s, large-scale clinical trials proved the efficacy and safety of hepatitis A vaccines [4, 5], and, by 1995, the first hepatitis A vaccine was licensed. Initially, the vaccine was targeted at groups at high risk for infection [6], which reduced the annual incidence of reported new cases from ~12/ 100,000 population (ranging cyclically between -9/100,000 and 14/100,000) before vaccination to as low as ~ 7/ 100,000 population by 1999. Implementation of this vaccination policy initiated a progressive, decade-long reduction in the annual incidence of new cases that was acceler-