title: Secular trends were considered in the evaluation of universal hepatitis B vaccination in Taiwan.
abstract: OBJECTIVE
  The objective was to evaluate time-trend bias in the context of a series of studies reporting that a national hepatitis B virus vaccination program (launched in mid-1980s) substantially reduced childhood hepatocellular carcinoma (HCC) incidence.
  
  
  METHODS
  We applied an age-period-cohort model to evaluate the relative importance of age, time-trend (period), and vaccination (cohort) effect, respectively, on the incidence and mortality rate of HCC in boys and girls in Taiwan from 1980 to 2009.
  
  
  RESULTS
  HCC incidence increased with age. The period effect analysis revealed that the incidence of HCC started to decrease in 1980s, leveled off in mid-1990s, and declined again in mid-2000s among boys. The period effect was flat among girls. Cohort effect analysis demonstrated that among boys, the incidence of HCC started to decrease by those born in 2000-2004, which was 15 years later than the first vaccinated cohort. Among girls, the incidence rate started to decline before the mass vaccination program was initiated. The analysis showed a decline in mortality for boys and girls born in 1980s.
  
  
  CONCLUSIONS
  Time trend may play a more important role than the universal vaccination program in interpretation of the observed early decreasing trend in HCC in children, especially among boys.
authors: Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, 5F, No. 17, Xu-Zhou Road, Taipei, Taiwan; Department of Internal Medicine, National Taiwan University Hospital, No. 7, Chung-Shan South Road, Section 1, Taipei, Taiwan; Department of Medicine, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, Section 1, Taipei, Taiwan.
authors: Chia-Hsuin
authors: CH
authors: Chang
authors: Department of Internal Medicine, National Taiwan University Hospital, No. 7, Chung-Shan South Road, Section 1, Taipei, Taiwan; Department of Medicine, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, Section 1, Taipei, Taiwan; Department of Internal Medicine, National Taiwan University Hospital Yun-Lin Branch, 579 Yun-Lin Road, Section 2, Dou-Liou City, Yun-Lin County, Taiwan. Electronic address: jouweilin@yahoo.com.
authors: Jou-Wei
authors: JW
authors: Lin
authors: Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, 5F, No. 17, Xu-Zhou Road, Taipei, Taiwan. Electronic address: yukangtu@ntu.edu.tw.
authors: Yu-Kang
authors: YK
authors: Tu
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D006528:Carcinoma, Hepatocellular / Q000453:epidemiology* / Q000401:mortality / Q000517:prevention & control / Q000821:virology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D017325:Hepatitis B Vaccines / Q000008:administration & dosage*; D019694:Hepatitis B, Chronic / Q000453:epidemiology* / Q000517:prevention & control; D006801:Humans; D017589:Immunization Programs; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008113:Liver Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000517:prevention & control / Q000821:virology; D008297:Male; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult
chemical_list: D017325:Hepatitis B Vaccines
keywords: Bias; Carcinoma; Hepatitis B; Hepatocellular; Incidence; Mortality; Vaccination