Humoral and cell-mediated immune responses in humans before and after revaccination with vaccinia virus

Twenty-six healthy males vaccinated 15 to 18 years ago with vaccinia virus were revaccinated. Blood samples were collected before vaccination and 3 weeks after. The lymphocytes were tested in a blast transformation assay with vaccinia antigen and phytohemagglutinin, and interferon production was measured. The sera were subjected to neutralization and antibody-dependent cell-mediated cytotoxicity (ADCC) tests. All results were compared with clinical responses. The only test showing immunity in all donors before vaccination was the ADCC. The other tests showed a very limited residual immunity or no immunity at all. After revaccination, immunity reactions were found in all tests in most of the donors. None of the tests made before vaccination could be used to predict clinical reactions. The ADCC is recommended as a sensitive serological test.