Multiple false-positive serologic tests for HIV, HTLV-1, and hepatitis C following influenza vaccination, 1991.

OBJECTIVE: (1) To assess factors associated with the occurrence of multiple false-positive viral enzyme-linked immunosorbent assays (ELISAs) for human immunodeficiency virus (HIV), human T-cell lymphotrophic virus type 1 (HTLV-1), and hepatitis C virus (HCV) among individual blood donors and (2) to determine the frequency and time course of this phenomenon.

DESIGN: Case-control study.

SETTING: A regional blood center.

PARTICIPANTS: Blood donors found to have multiple false-positive viral ELISAs (case donors) and randomly selected seronegative controls (control donors) who donated between October 31, 1991, and December 15, 1991. An additional random sample of 262 donation records was reviewed to calculate the proportion of donors who received influenza vaccine.

MAIN OUTCOME MEASURES: Multiple false-positive viral ELISAs, receipt of influenza vaccination formulated for the 1991-1992 influenza season, and follow-up ELISA results on serum samples obtained from case donors.

RESULTS: Among 17,941 donors, 10 case donors were identified. Nine of the 10 case donors received influenza vaccine, compared with three of 30 control donors (odds ratio [OR] = 81; 95% confidence interval [CI], 6 to 3670; P less than .001). Among nine case donors, the mean time between vaccination and blood donation was 26 days (range, 9 to 68 days). Follow-up ELISAs of serum samples from seven case donors obtained 52 to 130 days (mean, 75 days) after vaccination demonstrated reversion to HIV and HTLV-1 seronegativity in all but one specimen, with persistence of positive HCV ELISAs in four specimens. We estimate between 0.6% and 1.7% of blood donors who received influenza vaccine this season had multiple false-positive viral ELISAs.

CONCLUSIONS: The occurrence of multiple false-positive viral ELISAs among blood donors was associated with influenza vaccination, but was infrequent among vaccinees. This phenomenon is of short duration for HIV and HTLV-1, but may persist longer for HCV. We recommend influenza vaccinees not be deferred from blood donation. Blood donors with multiple false-positive viral ELISAs should be considered for future reentry as blood donors.