Has hepatitis A virus been transmitted by clotting factor concentrates among hemophiliacs in the United States?
Hepatitis A virus (HAV) infection occurred after administration of factor VIII concentrate in Europe associated with one manufacturing process. We determined if there was an excess prevalence of anti-HAV among hemophiliacs in the United States, and whether any infections here were potentially concentrate-associated. We observed clotting disorder patients and household members for up to 7 years at 6-month intervals. Selected specimens were titered for anti-HAV-immunoglobulin G content to distinguish whether they were passively or actively acquired. Our results show that anti-HAV prevalence was 20-25%, but males with clotting deficiencies had a 44% rate (p < 0.001). Passive anti-HAV (> or = 30 to < 950 mIU/ml) from intermediate-purity factor VIII may have protected against community HAV exposure. Factor IX concentrates, which contain no anti-HAV, did not protect and a few instances of past transmission are possible. Criteria for present-day concentrate-associated cases were developed; no
