Several assays show hepatitis B positivity soon after vaccination

Editor–The advent of the latest generation of assays for hepatitis B surface antigen (HBsAg) has been accompanied by a rise in the number of blood donors found to be positive for the antigen. Specific neutralisation has confirmed that these donors are HBsAg positive, but testing for antibody to hepatitis B core antigen (HBcAg) and for e antigen (HBeAg) and antibody has invariably proved fruitless. Such a serological pattern of reaction only to HBsAg is generally explained by a very early acute infection with hepatitis B virus before jaundice develops.

Since the introduction of the dynamic Auszyme assay (Abbott Laboratories, Delkenheim) in two of our regional transfusion centres, we have identified eight donations that have shown a confirmable HBsAg positive reaction in the absence of markers for HBc or HBe. A minimum of four weeks after donation, none of these donors had evidence of developing clinical hepatitis or of circulating HBsAg or any other marker of infection with hepatitis B virus. All donors had had a hepatitis B vaccination shortly before they donated blood (1). Subsequent blood samples from these donors were negative for HBsAg with no evidence of antibody to HBcAg but relatively weak concentrations of antibody to HBsAg.
  

Transient HBs antigenaemia in infants after hepatitis B vaccine has been given has been well documented.^{1 2} A weak positive HBsAg reaction in blood donors is uncommon but has been reported one to three days after vaccination.³ One of our donors reported a hepatitis B vaccination five days previously, which suggests that deferral of blood donation if donors have recently been vaccinated for hepatitis B may need to be extended beyond the current criterion of 48 hours.

The dynamic Auszyme assay was not the only assay found to be reactive with the eight positive donations. The Abbott PRISM HBsAg, Abbott Axsym, Ortho HBsAg-3 (Raritan, NJ, USA), Organon HBsAg Uniform II (Boxtel, Netherlands), and Murex HBsAg GE (Dartford, UK) HBsAg assays reacted to some of these samples.

Some diagnostic laboratories could obtain similar results in people who fail to admit recent hepatitis B vaccination and may misdiagnose early acute infection with hepatitis B virus. When a weak, neutralisable reaction to HBsAg is found in the absence of HBe markers and antibodies to HBcAg, a history of recent hepatitis B vaccination should be sought before a diagnosis is made.

B C Dow, Acting director,^a H Munro, Medical laboratory scientific officer 2,^a D Frame, Associate specialist,^b P Yates, Consultant ^c

^a Scottish National Blood Transfusion Service, Microbiology Reference Unit, Glasgow and West of Scotland Blood Transfusion Service, Law Hospital, Carluke, Lanarkshire ML8 5ES, ^b Glasgow and West of Scotland Blood Transfusion Service,, ^c Aberdeen and North East Scotland Blood Transfusion Service, Foresterhill, Aberdeen AB9 2ZW

1. Challapalli M, Naidu V, Cunningham DG. Hepatitis B surface antigenaemia in a newborn infant after vaccination. Pediatr Infect Dis J 1993;12:408-9. [Medline]

2. Challapalli M, Slosar M, Vasa R, Cunningham DG. Brief surface antigenaemia in newborn infants vaccinated with hepatitis B vaccine. Pediatr Infect Dis J 1993;12:878-9. [Medline]

3. Kloster B, Kramer R, Eastlund T, Grossman B, Zarvan B. Hepatitis B surface antigenaemia in blood donors following vaccination. Transfusion 1995;35:475-7. [Medline]