Although reported cases of hepatitis A virus (HAV) decreased significantly following availability of the HAV vaccine in 1996, increases observed in HAV cases since 2016 may be a sign that at-risk individuals are not receiving the vaccine prior to exposure. To obtain a better grasp on this trend and describe the increases in HAV cases in the US in recent years, Monique Foster, MD, and colleagues calculated the percentage change between the number of cases reported to CDC’s National Notifiable Diseases Surveillance System from 2013–2015 and those reported to NNDSS from 2016–2018. Their findings were published in Morbidity and Mortality Weekly Report.

“Overall, reports of hepatitis A cases increased 294% during 2016–2018 compared with 2013–2015,” says Dr. Foster, “with the majority of cases related to ongoing outbreaks affecting people who report drug use, homelessness, or both.” During that period, CDC tested nearly 4,300 specimens, of which 91% had detectable HAV RNA. Among that 91%, 84% were genotype IB, 15% were genotype IA, and less than 1% were genotype IIIA. Person-to-person outbreaks that started to be observed in 2017 were among individuals that the Advisory Committee on Immunization Practices (ACIP) recommends for vaccination, including people who use both injection and non-injection drugs and those experiencing homelessness. ACIP also recommends HAV vaccination for men who have sex with men and—as of June 2019—people living with HIV.

“Hepatitis A outbreaks among groups who are recommended to be vaccinated indicate there may be gaps in vaccination programs for vulnerable populations at risk,” notes Dr. Foster. “Given recent increases in hepatitis A cases, and the ongoing outbreaks nationwide, it is important that physicians continue to stay abreast of current ACIP recommendations for groups who should be vaccinated for HAV. Continued efforts to increase HAV vaccination coverage among the ACIP-recommended risk groups is vital to halting the current outbreaks and reducing overall incidence in the US.”