Thirty years of hepatitis A epidemiology and vaccine studies: A narrative review of lessons learned in Alaska.

Hepatitis A virus (HAV) is an RNA virus transmitted by fecal-oral contamination. HAV is usually asymptomatic in young children who shed the virus, leading to infection in susceptible adults who develop symptomatic hepatitis. This article reviews the epidemiology of HAV infection in Alaska and results of hepatitis A vaccine (HepA) studies conducted in Alaska, including evidence that routine early childhood HepA vaccination can eliminate transmission in an area that previously experienced repeat outbreaks. Historically, Alaska had periodic large HAV outbreaks. Alaska was the site of both Phase 3 and 4 clinical trials of the HepA vaccine, one of which demonstrated that only one dose of HepA vaccine administered to susceptible persons in communities experiencing an active outbreak could stop transmission in 4-8 weeks. Evidence indicates that the HepA vaccine offers protection for at least 25 years for most individuals, however, data on the durability of immunity beyond this period is lacking, particularly among people vaccinated as young children. We discuss future considerations for continued control of hepatitis A in Alaska.