title: Cost-effectiveness of an influenza vaccination program offering intramuscular and intradermal vaccines versus intramuscular vaccine alone for elderly.
abstract: Intradermal (ID) injection is an alternative route for influenza vaccine administration in elderly with potential improvement of vaccine coverage. This study aimed to investigate the cost-effectiveness of an influenza vaccination program offering ID vaccine to elderly who had declined intramuscular (IM) vaccine from the perspective of Hong Kong public healthcare provider.
  
  
  
  A decision analytic model was used to simulate outcomes of two programs: IM vaccine alone (IM program), and IM or ID vaccine (IM/ID program) in a hypothetic cohort of elderly aged 65 years. Outcome measures included influenza-related direct medical cost, infection rate, mortality rate, quality-adjusted life years (QALYs) loss, and incremental cost per QALY saved (ICER). Model inputs were derived from literature. Sensitivity analyses evaluated the impact of uncertainty of model variables.
  
  
  
  In base-case analysis, the IM/ID program was more costly (USD52.82 versus USD47.59 per individual to whom vaccine was offered) with lower influenza infection rate (8.71% versus 9.65%), mortality rate (0.021% versus 0.024%) and QALYs loss (0.00336 versus 0.00372) than the IM program. ICER of IM/ID program was USD14,528 per QALY saved. One-way sensitivity analysis found ICER of IM/ID program to exceed willingness-to-pay threshold (USD39,933) when probability of influenza infection in unvaccinated elderly decreased from 10.6% to 5.4%. In 10,000 Monte Carlo simulations of elderly populations of Hong Kong, the IM/ID program was the preferred option in 94.7% of time.
  
  
  
  An influenza vaccination program offering ID vaccine to elderly who had declined IM vaccine appears to be a highly cost-effective option.
authors.affiliation: School of Pharmacy, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
authors.forename: Man-Kit
authors.initials: MK
authors.lastname: Leung
authors.affiliation: School of Pharmacy, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong. Electronic address: joyceyou@cuhk.edu.hk.
authors.forename: Joyce H S
authors.initials: JH
authors.lastname: You
mesh_terms: D000368:Aged; D000914:Antibodies, Viral / Q000097:blood; D003362:Cost-Benefit Analysis; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D017589:Immunization Programs / Q000191:economics*; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000276:immunology; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D007271:Injections, Intradermal; D007273:Injections, Intramuscular; D009026:Mortality; D017063:Outcome Assessment, Health Care; D019057:Quality-Adjusted Life Years; D014611:Vaccination
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines
keywords: Cost-effectiveness; Elderly; Intradermal injection; Intramuscular injection; Microneedle; Seasonal influenza vaccine