title: Seroprevalence of Pandemic A(H1N1) pmd09 Virus Antibodies in Mexican Health Care Workers Before and After Vaccination.
abstract: OBJECTIVE
  In April 2009, a new strain of influenza A(H1N1) was identified in Mexico and in the U.S. In June 2009, WHO declared this a pandemic. Health care workers constituted a risk group for their close contact with infected individuals. The aim was to estimate seropositivity for A(H1N1)pdm09 in health staff at the Instituto Mexicano del Seguro Social.
  
  
  METHODS
  A two-stage cross-sectional study, before and after vaccination in the same workers, was performed on a random sample of health-care workers. A socio-occupational questionnaire was applied and serum antibodies against influenza A(H1N1)pdm09 were determined through neutralization of retroviral pseudotypes; two logistic regression models for both were constructed.
  
  
  RESULTS
  The average (median/mean) age of 1378 participants from 13 work centers was 41.7 years and 68.7% (947) were women. Seroprevalence for the first stage was 26.5% (365) (7.4-43%) vs. 20.8% (11) in a control group from the blood bank; for the second stage, the vaccinated group was 33% (215) (18.2-47%) and 27% (196) (11.6-50%) for the unvaccinated group. In regression models, seropositivity was associated with occupational exposure to suspected influenza infected patients, being physicians, and being vaccinated.
  
  
  CONCLUSIONS
  Seropositivity against pandemic virus is similar to what was reported, both for vaccinated (2.8-40.9%) and unvaccinated (18.8-64.7%). Low seroprevalence in the vaccinated group indicates that between 67% and 73% were susceptible to infection. Given the relatively low vaccine-induced seropositivity, it is imperative to increase, hygiene and safety for health staff and at-risk populations, and strengthen epidemiological surveillance.
authors: Occupational Health Research Unit, Centro Médico Nacional "Siglo XXI", Instituto Mexicano del Seguro Social, Mexico City, Mexico. Electronic address: gpeaguilarm@gmail.com.
authors: Guadalupe
authors: G
authors: Aguilar-Madrid
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Juan Arturo
authors: JA
authors: Castelán-Vega
authors: Occupational Health Research Unit, Centro Médico Nacional "Siglo XXI", Instituto Mexicano del Seguro Social, Mexico City, Mexico.
authors: Cuauhtémoc Arturo
authors: CA
authors: Juárez-Pérez
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Rosa María
authors: RM
authors: Ribas-Aparicio
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Iris
authors: I
authors: Estrada-García
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Laura
authors: L
authors: Baltierra-Jasso
authors: Immunology Research Unit, Hospital for Infectious Diseases, La Raza National Medical Center, Instituto Mexicano del Seguro Social, Mexico City, Mexico.
authors: Nicté
authors: N
authors: Cervantes-Servín
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Vanessa
authors: V
authors: Méndez-Ortega
authors: Academia de Salud Comunitaria, Promoción a la Salud. Universidad Autónoma de la Ciudad de México, Mexico City, Mexico.
authors: Luis C
authors: LC
authors: Haro-García
authors: Department of Workplace Health, Disability Division, Centro Médico Nacional "Siglo XXI", Instituto Mexicano del Seguro Social, Mexico City, Mexico.
authors: Francisco Raúl
authors: FR
authors: Sánchez-Román
authors: Department of Molecular Biomedicine, Centro de Investigación y Estudios Avanzados, Instituto Politécnico Nacional, Mexico City, Mexico.
authors: Vianney
authors: V
authors: Ortiz-Navarrete
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Luis H
authors: LH
authors: Fabila-Castillo
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Anastasia
authors: A
authors: Magaña-Hernández
authors: Education and Research, Specialties Hospital, Centro Médico Nacional "Siglo XXI", Instituto Mexicano del Seguro Social, Mexico City, Mexico.
authors: Adolfo
authors: A
authors: Chávez-Negrete
authors: Coordinación de Investigación en Salud, Centro Médico Nacional "Siglo XXI", Instituto Mexicano del Seguro Social, Mexico City, Mexico.
authors: Fabio Abdel
authors: FA
authors: Salamanca-Gómez
authors: Departments of Microbiology and Immunology, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional (IPN), Mexico City, Mexico.
authors: Alicia
authors: A
authors: Jiménez-Alberto
mesh_terms: D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000097:blood*; D001771:Blood Banks; D003430:Cross-Sectional Studies; D005260:Female; D006282:Health Personnel; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology* / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology*; D016015:Logistic Models; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D016273:Occupational Exposure; D010820:Physicians; D016036:Seroepidemiologic Studies; D011795:Surveys and Questionnaires; D014611:Vaccination; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines
keywords: Health care workers; Influenza A(H1N1)pdm09; Retroviral pseudotypes; Seroprevalence; Vaccination