title: Near disappearance of childhood invasive Haemophilus influenzae type b disease in Singapore.
abstract: BACKGROUND
  Haemophilus influenzae type b (Hib) conjugate vaccines have significantly limited Hib's disease impact in every country where it was introduced. We previously estimated invasive Hib disease incidence in Singapore at ∼4.4 per 100,000 children <5 years (from 1994 to 2003, period 1), but the vaccine was not included in the national childhood immunization schedule until May 2013 (although it was available privately). The current study aims to describe changes in Hib disease incidence and vaccine coverage prior to the introduction of the vaccine.
  
  
  METHODS
  We retrospectively reviewed all invasive Hib cases from January 2004 to December 2012 (period 2) and estimated population-based incidence rates. Vaccine coverage was estimated from vaccine sales for 1994-2003, and from National Immunisation Registry for 2004-2010.
  
  
  RESULTS
  There were 8 cases of invasive Hib disease in period 2, of whom 5 were <5 years. Invasive Hib incidence for period 2 was 0.57 per 100,000 children <5 years, representing an 86.4% reduction compared to period 1 (rate ratio 0.14, 95% confidence interval 0.06-0.26). However, for the later part of period 2 (2008-2012), incidence was 0.2 per 100,000 children <5 years; this represented a 95% reduction from period 1 (rate ratio 0.05, 95% confidence interval 0.01-0.18). Between periods 1 and 2, national Hib vaccine coverage rose from 22% to >80%, with >99% of children receiving combination Hib-containing vaccines.
  
  
  CONCLUSIONS
  Childhood invasive Hib disease has nearly disappeared from Singapore, despite the absence of universal mass vaccination. We believe this is likely due to excellent uptake of combination vaccines.
authors.affiliation: Infectious Disease Service, Department of Paediatric Medicine, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore 229899, Singapore. Electronic address: Thoon.Koh.Cheng@kkh.com.sg.
authors.forename: Koh Cheng
authors.initials: KC
authors.lastname: Thoon
authors.affiliation: Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore 229899, Singapore. Electronic address: Nancy.Tee.WS@kkh.com.sg.
authors.forename: Nancy Wen Sim
authors.initials: NW
authors.lastname: Tee
authors.affiliation: Research & Strategic Planning, Health Promotion Board, 3 Second Hospital Ave, Singapore 168937, Singapore. Electronic address: CHEW_Ling@hpb.gov.sg.
authors.forename: Ling
authors.initials: L
authors.lastname: Chew
authors.affiliation: Infectious Disease Service, Department of Paediatric Medicine, KK Women's and Children's Hospital, 100 Bukit Timah Road, Singapore 229899, Singapore. Electronic address: Chong.Chia.Yin@kkh.com.sg.
authors.forename: Chia Yin
authors.initials: CY
authors.lastname: Chong
mesh_terms: D016667:Bacterial Capsules; D002648:Child; D002675:Child, Preschool; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000517:prevention & control; D018073:Haemophilus Vaccines / Q000627:therapeutic use; D019741:Haemophilus influenzae type b; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D032541:Mass Vaccination; D012846:Singapore / Q000453:epidemiology; D018074:Vaccines, Conjugate / Q000627:therapeutic use
chemical_list: D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D018074:Vaccines, Conjugate
keywords: Children; Haemophilus influenzae type b; Singapore