A community outbreak of hepatitis A in a religious community in Indiana: failure of immune serum globulin to prevent the spread of infection

An outbreak of hepatitis A occurred in a religious community in Indiana, US A. Sixty-nine cases were ascertained among the 4466 residents over a year, and the highest attack rate was in children. The management of the outbreak included the widespread use of prophylactic immune serum globulin (ISG). D espite this, further cases occurred. To guide further ISG administration, a survey was undertaken to ascertain what proportion remained susceptible to HAV infection. From a random sample of 600 people in the affected communit y 440 saliva specimens (73 %) were obtained. Of these, 12.5 % were found to be immune (95 % confidence intervals from 9-16 %). No changes were made to the ISG administration policy. There was no evidence to suggest that admin istration of ISG had any effect on the duration of the outbreak. There was a low rate of symptomatic infection among young children (less than 10 year s); as ISG does not prevent the spread of the virus its use is not recommen ded in future outbreak situations.