Serial serum samples from a 2-year human trial of outer surface protein (Osp) A vaccine were analyzed by Borrelia burgdorferi growth-inhibition assay (GIA) and anti-OspA ELISA to assess the antibody responses of vaccine recipients and subjects with
Lyme disease. Although 74% of OspA recipients had a reciprocal GIA titer >/=64 after 3 vaccinations, none of the placebo recipients, even those with
Lyme disease, had a GIA titer this high. The correlation between GIA and ELISA titers after 3 doses of vaccine was.84; however, more vaccine recipients had an elevated ELISA titer paired with low GIA titer than had a low ELISA titer with a high GIA titer. OspA-vaccine recipients who acquired
Lyme disease had significantly lower serum GIA and ELISA titers after 3 immunizations than did age- and sex-matched OspA recipients without
Lyme disease. Thus, vaccinated subjects had antibodies to native antigen on viable cells, and antibody assays with this specificity may predict protection of vaccinees against infection.