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. 2020 Sep;31(5):628-635.
doi: 10.1097/EDE.0000000000001218.

The Impact of Vaccination Efforts on the Spatiotemporal Patterns of the Hepatitis A Outbreak in Michigan, 2016-2018

Andrew F Brouwer  1 , Jonathan L Zelner  1 , Marisa C Eisenberg  1 , Lynsey Kimmins  2 , Macey Ladisky  2 , Jim Collins  2 , Joseph N S Eisenberg  1
Affiliations

The Impact of Vaccination Efforts on the Spatiotemporal Patterns of the Hepatitis A Outbreak in Michigan, 2016-2018

Andrew F Brouwer et al. Epidemiology. 2020 Sep.

Abstract

Background: The United States is currently experiencing the largest hepatitis A virus (HAV) outbreak since the introduction of a vaccine in 1996. More than 31,000 cases have been reported since 2016. Although HAV had largely been considered a foodborne pathogen in recent years, this outbreak has been spread primarily through person-to-person transmission in urban settings and has been associated with homelessness and substance use. Michigan was one of the first states to report an outbreak, with 910 reported cases between August 2016 and December 2018.

Methods: We analyzed surveillance and vaccination data from Michigan using a disease transmission model to investigate how vaccine timing and coverage influenced the spatiotemporal patterns of the outbreak, distinguishing between Southeast Michigan, where the outbreak began, and the rest of the state.

Results: We estimated that vaccination had little impact in Southeast Michigan (3% cases averted [95% confidence interval (CI) = 1%, 8%]) but had a substantial impact in the rest of the state, preventing a larger outbreak (91% cases averted [95% CI = 85%, 97%]) lasting several more years.

Conclusions: Our results emphasize the value of targeting populations where local transmission is not yet sustained rather than populations where transmission is already waning. Simulation modeling can aid in proactive rather than reactive decision-making and may help direct the response to outbreaks emerging in other states. See video abstract: http://links.lww.com/EDE/B704.

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Figures

Figure 1:
Figure 1:
a) Reported cases of hepatitis A in Southeast Michigan (Macomb, Oakland, and Wayne Counties, including Detroit City). b) Reported cases of hepatitis A outside of Southeast Michigan (all other Michigan counties). c) Reported number of hepatitis A vaccine doses (private and public) administered in Southeast Michigan. d) Reported number of hepatitis A vaccine doses (private and public) administered outside of Southeast Michigan. Vaccine data is only recorded for those age 19 or older.
Figure 2:
Figure 2:
Schematic of the metapopulation infectious disease model for the Michigan hepatitis A outbreak. Solid arrows represent movement of individuals between model compartments (disease states) while dotted arrows show how infectious individuals contribute to new infections through disease transmission. The capped line segments indicate the compartments that correspond to the observed data.
Figure 3:
Figure 3:
Model fit of the Michigan hepatitis A outbreak a) within Southeast Michigan and b) outside of Southeast Michigan. The ribbons give the confidence intervals for the maximum-likelihood trajectory using likelihood-based estimates of the 95% confidence parameter region.
Figure 4:
Figure 4:
a) The estimated basic reproduction numbers R0 depend on the size of the at-risk populations in Southeast Michigan (MI) and outside Southeast Michigan. b) The fraction of cases averted in the hepatitis A outbreak in Southeast Michigan depend on the timing of increased vaccination and vaccination coverage parameter for the at-risk population in Southeast Michigan.
See this image and copyright information in PMC

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