Lack of evidence of endogenous avian leukosis virus and endogenous avian retrovirus transmission to measles, mumps, and rubella vaccine recipients

The identification of endogenous avian leukosis virus (ALV) and endogenous avian retrovirus (EAV) in chick cell-derived measles and mumps vaccines in current use has raised concern about transmission of these retroviruses to vaccine recipients. We used serologic and molecular methods to analyze spec imens from 206 recipients of measles, mumps, and rubella (MMR) vaccine for evidence of infection with ALV and EAV. A Western blot assay for detecting antibodies to endogenous ALV was developed and validated. All serum samples were negative for antibodies to endogenous ALV by Western blot analysis. P eripheral blood lymphocyte samples from 100 vaccinees were further tested b y polymerase chain reaction for both ALV and EAV proviral sequences; all we re negative. Matching serum samples were tested by reverse transcriptase po lymerase chain reaction for ALV and EAV RNA, and all 100 samples were negat ive, providing no evidence of viremia. These findings do not indicate the p resence of either ALV or EAV infection in MMR vaccine recipients and provid e support for current immunization policies.