seronegativeadjective
/ˌsɪə.rɘʊˈneɡ.ə.tɪv//ˌsɪr.oʊˈneɡ.ə.t̬ɪv/specializedshowing a negative result of a blood test for a particular antibody (= a substance in the blood that fights a disease):
children who remain seronegative after polio vaccinations