title: Identification of primary and secondary measles vaccine failures by measurement of immunoglobulin G avidity in measles cases during the 1997 São Paulo epidemic.
abstract: Despite almost universal use of measles vaccines in recent decades, epidemics of the disease continue to occur. Understanding the role of primary vaccine failure (failure to seroconvert after vaccination) and secondary vaccine failures (waning immunity after seroconversion) in measles epidemics is important for the evaluation of measles control programs in developing countries. After a measles epidemic in São Paulo, Brazil, 159 cases previously confirmed by detection of specific immunoglobulin M (IgM) antibodies were tested for IgG avidity, and a secondary immune response, defined by an IgG avidity index of at least 30%, was established in 30 of 159 (18.9%) patients. Among the 159 patients, 107 (67.3%) had not been vaccinated and 52 (32.7%) had received one or more doses of measles vaccine. Of the 107 unvaccinated patients, 104 (97.2%) showed a primary immune response, defined as an IgG avidity index of less than 30%. Among the 52 patients with documented vaccination, 25 (48.1%) showed a primary immune response and 27 (51.9%) showed a secondary immune response, thereby constituting a secondary vaccine failure. Primary vaccine failure was observed in 13 of 13 patients vaccinated prior to 1 year of age and in 43.5 and 12.5%, respectively, of patients receiving one or two doses after their first birthdays. These results provide evidence that measurement of IgG avidity can be used to distinguish between primary and secondary vaccine failures in vaccinated patients with measles; the method can also be a useful tool for the evaluation of measles control programs.
authors.affiliation: Instituto de Medicina Tropical de São Paulo-LIM-HC, Departamento de Moléstias Infecciosas e Parasitárias, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil. cpannuti@usp.br
authors.forename: Cláudio S
authors.initials: CS
authors.lastname: Pannuti
authors.forename: Ricardo José
authors.initials: RJ
authors.lastname: Morello
authors.forename: José Cássio de
authors.initials: JC
authors.lastname: Moraes
authors.forename: Suely Pires
authors.initials: SP
authors.lastname: Curti
authors.forename: Ana Maria S
authors.initials: AM
authors.lastname: Afonso
authors.forename: Maria Cláudia Corrêa
authors.initials: MC
authors.lastname: Camargo
authors.forename: Vanda A U F de
authors.initials: VA
authors.lastname: Souza
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D000915:Antibody Affinity; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D006801:Humans; D007115:Immunization Schedule; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D008457:Measles / Q000453:epidemiology* / Q000276:immunology / Q000517:prevention & control*; D008458:Measles Vaccine / Q000008:administration & dosage / Q000276:immunology*; D008459:Measles virus / Q000276:immunology*; D017211:Treatment Failure
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D008458:Measles Vaccine