Silent hepatitis-B immunization in laboratory technicians.

The present investigation was initiated to assess the demand for vaccination against hepatitis-B in a department of clinical chemistry. One hundred and twenty-eight employees enrolled for the test programme consisting primarily of screening for hepatitis-B antigen (HBsAg) and antibody to hepatitis-B surface antigen (anti-HBs). Surprisingly it was found, that 8 persons out of 58 who had also participated in a screening survey in 1978 had developed anti-HBs. These persons, who had no history of hepatitis, were also positive for antibodies towards the core antigen of hepatitis-B (anti-HBc). A seroconversion rate of 1,53/100/year for this material was calculated. Six persons who had contracted hepatitis-B during an epidemic 14 years previously, presented with very weak anti-HBs reactivity, but were positive for anti-HBc indicating, that anti-HBc was the more stable indicator of past HBV infection. The cost-effectiveness of vaccination against HBV seems disputable compared with other protective measures. The high incidence of silent seroconversion indicates a chronic exposure to virus among the laboratory personnel. Therefore, safety precautions against virus exposure are highly recommended.