COVID-19　remains　as　a　major　threat　to　human　society.　A　reliable,　sensitive,　rapid,　and　low　requirement　assay　for　serum　neutralizing　antibodies　is　needed　as　a　pandemic　management　tool　for　estimation　of　revaccination　time　and　implementation　of　“immune　passport”.　Using　gold　nanoparticle　(AuNR)　as　an　immunosensor,　we　have　established　a　semi-quantitative,　instrument-free　assay　for　measuring　antibody　level　against　SRAS-CoV-2　spike1　(S1)　receptor　binding　domain　(RBD)　from　fingertip　blood　samples.　The　testing　results　by　the　developed　method　correlated　well　with　those　obtained　from　conventional　ELISA　assay,　indicating　reliable　quantitation　could　be　achieved　without　use　of　plate　reader.　A　declined　of　immunoglobulin　G　(IgG)　antibody　associated　with　vaccination　time　was　observed,　which　agreed　well　with　the　data　from　other　reports.　The　developed　method　provides　a　potentially　complementary　strategy　for　on-site　measurement　of　COVID-19　antibodies.　©　2022　Elsevier　B.V.