Effectiveness of hepatitis A vaccine in a former frequently affected community: 9 years' followup after the Monroe field trial of VAQTA.

The Kiryas Joel community in Monroe, N.Y. was the site of the first clinical trial which proved the protective efficacy of hepatitis A vaccine. The vaccine used was VAQTA J. Med. Virol (hepatitis A vaccine, inactivated). In the 9 years since the trial ended vaccination of infants reaching 2 years of age has continued along with monitoring for hepatitis A cases. The prevaccine pattern of frequent outbreaks has converted to a sustained pattern of no outbreaks, despite sporadic introduction of hepatitis A into the community in nonvaccinees. Community use of VAQTA in children 2 years of age and older has proven capable of providing long-term prevention of hepatitis A outbreaks in a formerly frequently affected community despite prolonged sporadic introduction of the virus.