Estimating herd immunity thresholds for hepatitis A: A 16-state analysis to inform vaccination strategies among people who inject drugs (PWID)

This fact sheet discusses how research from the University of California San Diego and published in Clinical Infectious Diseases, estimates the hepatitis A vaccination coverage needed to prevent outbreaks among people who inject drugs (PWID). Analyzing surveillance data from 16 states with recent hepatitis A outbreaks linked to PWID, the study found that vaccination coverage of at least 80% may be necessary to reliably achieve herd immunity—though some states, such as West Virginia, may require higher levels. With vaccination rates in this population still low and more than half of PWID at risk, the findings underscore the urgent need for targeted vaccination strategies to prevent future outbreaks.