Shift in hepatitis A outbreaks ‘unprecedented’ in HAV vaccine era, CDC reports
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Recent and ongoing outbreaks associated with person-to-person transmission have marked a shift in hepatitis A virus epidemiology in the United States, according to data published in Morbidity and Mortality Weekly Report.
“Since 2016, the United States has experienced widespread hepatitis A outbreaks associated with person-to-person transmission,” Monique A. Foster, MD, of the division of global health protection at the CDC Center for Global Health, and colleagues wrote. “Hepatitis A outbreaks have been reported in 37 states, involving approximately 44,650 cases, 27,250 hospitalizations, and 415 deaths as of September 23, 2022.”
After the introduction of an HAV vaccine in 1996, there was an approximate 97% decline in HAV infection rates in the U.S. through 2015. Prior to the vaccine’s introduction, transmission was largely spread from asymptomatic children, and HAV affected a disproportionate amount of underrepresented racial and ethnic groups.
The rise in cases since 2016, however, have occurred almost exclusively in adults — predominantly among white men aged 30 to 49 years — with illicit drug use and homelessness named as risk factors, the report found.
In its analysis, the CDC characterized demographic, risk factor and clinical outcome data from 37,553 outbreak-associated HAV cases in 33 states between Aug. 1, 2016, and Dec. 31, 2020. Drug use (56%), homelessness (14%) and hospitalization (61%) were among reported risk factors, as was recent incarceration (12%), international travel (3%) and self-identification as a man who has sex with men (5%). Also, 380 deaths were reported.
Considering demographics, 62% of these HAV cases were in men, of whom 81% were white and 58% were aged 30 to 49 years, with a median age of 38 years.
“The outbreaks described in this report are unprecedented in the hepatitis A vaccine era,” the researchers wrote. “Proactive vaccination of adults at increased risk for HAV infection or adverse consequences of infection is critical to prevent outbreaks and serious illness.”
In response to these outbreaks, the CDC partnered with state and local health departments to implement a large-scale, multidisciplinary response to control outbreaks stemming from person-to-person transmission, which included nontraditional vaccination strategies to reach disproportionately affected populations. Partnering with trusted local organizations also helped mitigate mistrust and vaccine hesitancy, the researchers wrote.
As of September 2022, these efforts led to the end of outbreaks in 24 states and a decrease in HAV cases in 13 states.
“Disproportionately affected populations often experience stigma, mistrust and societal barriers that limit adequate access to the health care system,” the researchers wrote. “Continued improvements in vaccination infrastructure, immunization information systems, and education and outreach are critically needed to build vaccine confidence and improve vaccine delivery in nontraditional settings.”
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