Hepatitis A person-to-person outbreaks: Epidemiology, morbidity burden, and factors associated with hospitalization - Multiple States, 2016-2019.

BACKGROUND Since 2016, the US has experienced person-to-person hepatitis A outbreaks unprecedented in the vaccine era. The proportion of cases hospitalized in these outbreaks exceeds historical national surveillance data. METHODS We described the epidemiology, characterized the reported increased morbidity, and identified factors associated with hospitalization during the outbreaks by reviewing a 10% random sample of outbreak-associated hepatitis A cases in Kentucky, Michigan, and West Virginia-three heavily affected states. We calculated descriptive statistics and conducted age-adjusted log-binomial regression analyses to identify factors associated with hospitalization. RESULTS Participants in the random sample (n=817) were primarily male (62.5%) with mean age of 39.0 years; 51.8% were hospitalized. Among those with available information, 73.2% reported drug use, 14.0% were experiencing homelessness, 29.7% were currently or recently incarcerated, and 61.6% were epidemiologically linked to a known outbreak-associated case. Residence in Michigan (adjusted risk ratio [aRR] 1.8), being a man who has sex with men (aRR 1.5), non-injection drug use (aRR 1.3), and homelessness (aRR 1.3) were significantly (p<0.05) associated with hepatitis A-related hospitalization. CONCLUSIONS Our findings support current Advisory Committee on Immunization Practices recommendations to vaccinate all persons who use drugs, men who have sex with men, and persons experiencing homelessness against hepatitis A.