MULTIPLE FALSE REACTIONS IN VIRAL ANTIBODY SCREENING ASSAYS AFTER INFLUENZA VACCINATION

In December 1991, US blood centers reported an unusual increase in don ations that tested falsely reactive for antibodies to two or more (mul tiple false positive) of the following viruses: human immunodeficiency virus type 1 (HIV-1), human T-cell lymphotrophic virus type I (HTLV-I ), and hepatitis C virus. Many of these donations were from people who had recently received the 1991-1992 influenza vaccine, raising the po ssibility that this vaccine had somehow specifically caused the proble m of multiple false reactivity, A case-control study of 101 affected d onors and 191 matched controls found that recent receipt of any brand of influenza vaccine was significantly associated with testing multipl e false positive (p < 0.05), as was a history of recent acute illness (p < 0.05) and of allergies (p < 0.05). Surveillance for monthly rates of multiple reactive donations from May 1990 through December 1992 li nked the seasonal cluster of multiple false-positive donations to the use of viral screening test kits thought to react nonspecifically to d onor immunoglobulin M. There was no similar increase in multiple false -positive donations during the 1992-1993 influenza vaccination season after the HIV-1 and hepatitis C virus tests were replaced; however, th e number of donations that were falsely reactive for only HTLV-I almos t doubled, indicating that false reactivity was not specifically assoc iated with the 1991-1992 influenza vaccine. Retesting of affected dono rs found that the duration of HTLV-I and hepatitis C virus false react ivity was 3-6 months. The cluster of multiple false-positive donations in 1991 was most likely caused by the test kits used, rather than by the influenza vaccine.