A collaborative case control study of sporadic hepatitis A in England.

A case control study of sporadic hepatitis A was carried out in 201 districts in England from July 1990 to June 1991. The aims were to determine the risk factors associated with the infection and to identify individuals or groups who might benefit from prophylactic measures, such as human normal immunoglobulin or hepatitis A vaccine. Factors associated with risk of hepatitis A included travel abroad (odds ratio (OR) 19.8; 95% confidence interval (CI) 4.87-80.6), a household contact with hepatitis A (OR 13.5; 95% CI 6.49-28.0) and sharing a household with a child aged 3 to 10 years (OR 1.57; 95% CI 1.1-2.22). This study provided no clear evidence of increased risk in health care workers, teachers, or other occupational groups. A non-significant trend towards an increased risk in nursery nurses and child minders aged 20 to 29 years was observed. Pre-exposure prophylaxis with hepatitis A vaccine may be considered for people who travel frequently to areas where hepatitis A is highly or moderately endemic. Post-exposure prophylaxis with human normal immunoglobulin should be given to contacts of known cases in accordance with national guidelines. Immunoglobulin alone has been recommended in outbreaks, but the use of vaccine alone or combined with immunoglobulin should be evaluated.