Estimating vaccination threshold and impact in the 2017-2019 hepatitis A virus outbreak among persons experiencing homelessness or who use drugs in Louisville, Kentucky, United States

Details

• Alternative Title:
  Vaccine
• Personal Author:
  Dankwa, Emmanuelle A. ; Donnelly, Christl A. ; Brouwer, Andrew F. ; Zhao, Rui ; Montgomery, Martha ; Weng, Mark K. ; Martin, Natasha K.
• Description:
  Background ; Between September 2017 and June 2019, an outbreak of hepatitis A virus (HAV) occurred in Louisville, Kentucky, resulting in 501 cases and 6 deaths, predominantly among persons who experience homelessness or who use drugs (PEH/PWUD). The critical vaccination threshold (Vc) required to achieve herd immunity in this population is unknown. We investigated Vc and vaccination impact using epidemic modeling. ; Methods ; To determine which population subgroups had high infection risks, we employed a technique based on comparing the proportion of cases arising before and after the epidemic peak. We developed a dynamic deterministic model of HAV transmission among PEH/PWUD to estimate the basic reproduction number (R0), herd immunity threshold, Vc and the effect of timing of the vaccination intervention on epidemic and economic outcomes. ; Results ; Of the 501 confirmed or probable cases, 385 (76.8%) were among PEH/PWUD. Among PEH/PWUD and within the general population, homelessness was a significant risk factor for infection in the initial stages of the outbreak (odds ratios for homeless versus not homeless: 2.62; 95% confidence interval (CI): 1.62-4.25 for PEH/PWUD and 2.39; 95% CI: 1.51-3.78 for all detected cases). Our estimate for R0 ranges between 2.85 and 3.54, corresponding to an estimate of 69% (95% CI: 65-72) for herd immunity threshold and 76% (95% CI: 72%-80%) for Vc, assuming a vaccine with 90% efficacy. The observed vaccination program was estimated to have averted 30 hospitalizations (95% CI: 19-43), associated with over US$490,000 (95% CI: $310,000–700,000) in hospitalization cost. Greater impact was observed with earlier and faster vaccination implementation. ; Conclusions ; Vaccination coverage of at least 77% is likely required to prevent outbreaks of HAV among PEH/PWUD in Louisville, assuming a 90% vaccine efficacy. Proactive hepatitis A vaccination programs among PEH/PWUD will maximize health and economic benefits of these programs and reduce the likelihood of another outbreak.
• Subjects:
  • Disease Outbreaks
  • Hepatitis A
  • Hepatitis A virus
  • Ill-Housed Persons
  • Humans
  • Kentucky
  • Pharmaceutical Preparations
  • United States
  • Vaccination
  • Vaccine Efficacy
• Keywords:
  • hepatitis A
  • critical vaccination coverage
  • persons who experience homelessness or who use drugs
  • herd immunity
  • dynamic modeling
• Source:
  Vaccine. 39(49):7182-7190
• Pubmed ID:
  34686394
• Pubmed Central ID:
  PMC9128446
• Document Type:
  Journal Article
• Funding:
  CC/CDC HHSUnited States/ ; UL1 TR001442/TR/NCATS NIH HHSUnited States/ ; R01 AI147490/AI/NIAID NIH HHSUnited States/ ; P30 AI036214/AI/NIAID NIH HHSUnited States/ ; MR/R015600/1/MRC_/Medical Research CouncilUnited Kingdom/ ; U01 GM110712/GM/NIGMS NIH HHSUnited States/
• Volume:
  39
• Issue:
  49
• Download URL:
  https://stacks.cdc.gov/view/cdc/117712/cdc_117712_DS1.pdf
• File Type:
  [PDF - 594.90 KB]
• Collection(s):
  CDC Public Access
• Main Document Checksum:
  urn:sha-512:fcffb336aadcbef0e054efe1c7e7f2b14b84750d81ea029eeeec7a12740d0fd6112d32d8895cba6de89ba1afa8d8f1b5a4e95cdf74693d009bfccba0738ec632