title: [Herd immunity against rubella according to a survey of the population in Medellin, Colombia].
abstract: OBJECTIVE
  Calculate the critical proportion (Pc) for achieving herd immunity based on a 2009 population study conducted in Medellin, Colombia, by age, globally and disaggregated by sex, location, and socioeconomic stratum.
  
  
  METHODS
  A survey of seroprevalence in the population was conducted by means of a random sample of 2 124 individuals aged 6 to 64 that was representative of age, sex, and location. The basic reproduction number was estimated using a quadratic regression of the average IgG titers for rubella by age in unvaccinated individuals with titers greater than or equal to 15 IU/ml. The effective reproduction number (Re) was calculated with the data on the weighted proportion of protection by age, sex, location, and socioeconomic stratum.
  
  
  RESULTS
  Overall, the Pc was 90.0% (95% CI, 88.6-95.2%) and the Re was 0.95 (95% CI, 0.8-1.8), for a weighted proportion of protection of 89.4% (95% CI, 86.8- 91.6%). Protection was lower than the expected Pc in both sexes, in high and low socioeconomic strata, and in the rural area. In the urban area, protection was greater than the Pc (89.4%, with a 95% CI, 86.6-91.7%, compared to 87.4% and a 95% CI, 85.2-87.8%).
  
  
  CONCLUSIONS
  The urban area has made progress toward herd immunity, but the overall proportion of protection in women, the rural area, and the high socioeconomic strata must be increased. The effective number may be greater than one, indicating the potential for the spread of the disease.
authors.affiliation: Grupo de epidemiología, Universidad de Antioquia, Medellín, Colombia. doracely@saludpublica.udea.edu.co
authors.forename: Doracelly
authors.initials: D
authors.lastname: Hincapié Palacio
authors.forename: Juan
authors.initials: J
authors.lastname: Ospina Giraldo
authors.forename: Viviana
authors.initials: V
authors.lastname: Lenis Ballesteros
authors.forename: Marta C
authors.initials: MC
authors.lastname: Ospina Ospina
authors.forename: Marta
authors.initials: M
authors.lastname: Arroyave Cadavid
authors.forename: Nora
authors.initials: N
authors.lastname: Hoyos Muñoz
authors.forename: Rita
authors.initials: R
authors.lastname: Almanza Payares
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000914:Antibodies, Viral / Q000097:blood*; D002648:Child; D003105:Colombia; D005260:Female; D006306:Health Surveys; D006801:Humans; D032521:Immunity, Herd / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D012409:Rubella / Q000276:immunology*; D012412:Rubella virus / Q000276:immunology; D012424:Rural Population; D012494:Sampling Studies; D016036:Seroepidemiologic Studies; D012959:Socioeconomic Factors; D014505:Urban Population; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G