title: Influenza vaccine effectiveness against medically-attended influenza illness during the 2012-2013 season in Beijing, China.
abstract: BACKGROUND
  Influenza vaccine coverage remains low in China, and there is limited information on the preventive value of local vaccination programs.
  
  
  METHODS
  As part of influenza virological surveillance in Beijing, China during the 2012-2013 influenza season, we assessed the vaccine effectiveness (VE) of one or more doses of trivalent inactivated influenza vaccine (IIV3) in preventing medically-attended influenza-like-illness (ILI) associated with laboratory-confirmed influenza virus infection using a test-negative case-control design. Influenza vaccination was determined based on self-report by adult patients or the parents of child patients.
  
  
  RESULTS
  Of 1998 patients with ILI, 695 (35%) tested positive for influenza viruses, including 292 (42%) A(H3N2), 398 (57%) A(H1N1)pdm09, and 5 (1%) not (sub)typed influenza viruses. The rate of influenza vaccination among all patients was 4% (71/1998). Among influenza positive patients, 2% (57/1303) were vaccinated compared to 4% (14/695) among influenza negative patients, resulting in VE for one or more doses of vaccine (adjusted for age, sex, week, and days since illness onset) against all circulating influenza viruses of 52% (95% CI=12-74%). A significant adjusted VE for one or more doses of vaccine for all ages against A(H1N1)pdm09 of 59% (95% CI, 8-82%) was observed; however, the VE against A(H3N2) was 43% (95% CI, -30% to 75%). The point estimate of VE was 59% (95% CI, 19-79%) for those aged <60 years, but a negative VE point estimate without statistical significance was observed among those aged ≥60 years.
  
  
  CONCLUSIONS
  IIV3 conferred moderate protection against medically-attended influenza in Beijing, China during the 2012-2013 season, especially against the A(H1N1)pdm09 strain and among those aged <60 years old.
authors.affiliation: Beijing Center for Disease Prevention and Control, Beijing, China; Beijing Research Center for Preventive Medicine, Beijing, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Yang
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Thompson
authors.affiliation: Beijing Center for Disease Prevention and Control, Beijing, China; Beijing Research Center for Preventive Medicine, Beijing, China.
authors.forename: Chunna
authors.initials: C
authors.lastname: Ma
authors.affiliation: Beijing Center for Disease Prevention and Control, Beijing, China; Beijing Research Center for Preventive Medicine, Beijing, China.
authors.forename: Weixian
authors.initials: W
authors.lastname: Shi
authors.affiliation: Beijing Center for Disease Prevention and Control, Beijing, China; Beijing Research Center for Preventive Medicine, Beijing, China.
authors.forename: Shuangsheng
authors.initials: S
authors.lastname: Wu
authors.affiliation: Beijing Center for Disease Prevention and Control, Beijing, China; Beijing Research Center for Preventive Medicine, Beijing, China.
authors.forename: Daitao
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Beijing Center for Disease Prevention and Control, Beijing, China; Beijing Research Center for Preventive Medicine, Beijing, China. Electronic address: bjcdcxm@126.com.
authors.forename: Quanyi
authors.initials: Q
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D053122:Influenza A Virus, H3N2 Subtype; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D018571:Sentinel Surveillance; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines
keywords: China; Influenza; Influenza-like illness; Vaccine effectiveness