Emmanuelle A Dankwa1, Christl A Donnelly2, Andrew F Brouwer3, Rui Zhao4, Martha P Montgomery5, Mark K Weng5, Natasha K Martin6. 1. Department of Statistics, University of Oxford, 24-29 St Giles', Oxford OX1 3LB, UK. Electronic address: dankwa@stats.ox.ac.uk. 2. Department of Statistics, University of Oxford, 24-29 St Giles', Oxford OX1 3LB, UK; MRC Centre for Global Infectious Disease Analysis, Imperial College London, St. Mary's Campus, Norfolk Place, London W2 1PG, UK. 3. Department of Epidemiology, University of Michigan, 1415 Washington Heights, Ann Arbor, MI 48109-2029, USA. 4. Louisville Metro Department of Public Health and Wellness, 400 E Gray St, Louisville, KY 40202, USA. 5. Division of Viral Hepatitis, U.S. Centers for Disease Control and Prevention, 1600 Clifton Road NE, Mailstop US12-3, Atlanta, GA 30329-4018, USA. 6. Division of Infectious Diseases and Global Public Health, University of California San Diego, 9500 Gilman Drive, CA 92093, USA; Population Health Sciences, University of Bristol, Queens Road Bristol BS8 1QU, UK.
Abstract
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, across subgroups. We also 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.
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, across subgroups. We also 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.
Authors: Thierry P Van Effelterre; Thomas K Zink; Bernard J Hoet; William P Hausdorff; Philip Rosenthal Journal: Clin Infect Dis Date: 2006-06-12 Impact factor: 9.079
Authors: Noele P Nelson; Mark K Weng; Megan G Hofmeister; Kelly L Moore; Mona Doshani; Saleem Kamili; Alaya Koneru; Penina Haber; Liesl Hagan; José R Romero; Sarah Schillie; Aaron M Harris Journal: MMWR Recomm Rep Date: 2020-07-03
Authors: Peng-Jun Lu; Mei-Chuan Hung; Anup Srivastav; Lisa A Grohskopf; Miwako Kobayashi; Aaron M Harris; Kathleen L Dooling; Lauri E Markowitz; Alfonso Rodriguez-Lainz; Walter W Williams Journal: MMWR Surveill Summ Date: 2021-05-14
Authors: Xu-Sheng Zhang; Jason J Ong; Louis Macgregor; Tatiana G Vilaplana; Simone T Heathcock; Miranda Mindlin; Peter Weatherburn; Ford Hickson; Michael Edelstein; Sema Mandal; Peter Vickerman Journal: Lancet Reg Health Eur Date: 2022-06-17