title: Epidemiology of hepatitis B infection in Finland: Implications for immunisation policy.
abstract: We describe the current epidemiology of acute and chronic hepatitis B infections in Finland. We estimate the total incidence of chronic hepatitis B following from the current incidence of acute infections and the influx of chronic carriers of hepatitis B associated with net immigration. We evaluate the incidence of hepatitis B infections preventable by a universal vaccination programme among infants.
  
  
  
  We analysed hepatitis B cases reported to the National Infectious Disease Register during 2004-2012 and used pre-developed methods to adjust for acute asymptomatic infections. We estimated the projected incidence of chronic infection by applying age-specific risks of chronic infection to the estimated incidence of acute infection. We estimated the influx of chronic carriers associated with immigration by utilising data on immigration during 2004-2012 and the WHO regional estimates of carriage prevalence.
  
  
  
  The estimated incidence of acute hepatitis B infection in Finland, adjusted for asymptomatic infections, was 1.67 per 100,000 per year (95% Crl 1.43-1.94) which is 4.2-fold to the register-based incidence. The estimated lifetime risks of acute and chronic hepatitis B infections were 0.13% and 0.01%, respectively. We estimated that annually seven new chronic infections would result from infections acquired in Finland. These new chronic infections accounted for 1.2% of the total incidence of chronic infections. We estimated that eventually three chronic infections per year would be potentially preventable by a universal infant vaccination programme.
  
  
  
  Partly due to the fact that hepatitis B infections in neonates and in children are rare, a very limited number of chronic hepatitis B infections resulted from infection acquired within the country. A vast majority of chronic hepatitis B infections occurred among foreign-born persons and were therefore not preventable by a universal infant immunisation programme in Finland. Even with a targeted immunisation programme, the incidence of hepatitis B infection has remained low.
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, P.O. Box 30, FI-00271 Helsinki, Finland. Electronic address: tanja.karvonen@thl.fi.
authors.forename: Tanja
authors.initials: T
authors.lastname: Karvonen
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, P.O. Box 30, FI-00271 Helsinki, Finland; Department of Mathematics and Statistics, University of Turku, FI-20014, Finland. Electronic address: kari.auranen@thl.fi.
authors.forename: Kari
authors.initials: K
authors.lastname: Auranen
authors.affiliation: Department of Infectious Diseases, National Institute for Health and Welfare, P.O. Box 30, FI-00271 Helsinki, Finland. Electronic address: markku.kuusi@thl.fi.
authors.forename: Markku
authors.initials: M
authors.lastname: Kuusi
authors.affiliation: Department of Health Protection, National Institute for Health and Welfare, P.O. Box 30, FI-00271 Helsinki, Finland. Electronic address: tuija.leino@thl.fi.
authors.forename: Tuija
authors.initials: T
authors.lastname: Leino
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D000076263:Communicable Diseases, Imported / Q000453:epidemiology*; D004641:Emigration and Immigration; D005260:Female; D005387:Finland / Q000453:epidemiology; D006291:Health Policy; D006509:Hepatitis B / Q000453:epidemiology* / Q000517:prevention & control*; D006801:Humans; D017589:Immunization Programs; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D055815:Young Adult
keywords: Epidemiology; HBV; Hepatitis B; Immunisation; Vaccination