RESUMEN
We evaluated the seroprevalence of measles antibody and response to measles re-immunization in 590 previously vaccinated adolescents and young adults; 263 were seronegative. To differentiate between primary and secondary vaccine failure, anti- measles IgM and IgG titres were assessed again 2- 4 weeks after revaccination in 144 [105 seronegative, 39 seropositive] individuals: 75 seronegative participants responded to revaccination anamnestically [P < 0.001] and developed immunity 11 also showed IgM response [probably primary vaccine failure immunity]; 38 seropositive participants, remained seroprotected without significant increase in antibody titre [P = 0.577]. Primary vaccine failure was 4.7%; secondary vaccine failure was 27.1%. After revaccination, 87.3% were seroprotected