Guo Y, Zhang L, Feng D, et al. - Researchers sought to determine the effects of one dose of live attenuated hepatitis A vaccine in a developing country. An analysis was performed of the listed cases of hepatitis A virus (HAV) infection from 2005 to 2018 in Henan province, China. The childhood immunization information management system provided data of vaccinated children for assessment. In six counties and districts of Henan province, they randomly conducted questionnaire survey and blood sample collection to examine the prevalence of HAV lgG among the population aged 0-70 years. In 2008, initiation of expansion of the program on immunization was observed in Henan province, and one dose of live attenuated hepatitis A vaccine (HepA-L) was provided to children aged 18 months. The data revealed a large reduction in HAV infections in Henan province from 2008 onward in response to the initiation of this immunization program of HepA-L. Since 2008, a cumulative decrease in the HAV incidence was observed from 4,576 to 237 in 2018, indicating a 94.8% decrease, which was especially pronounced among adolescents (98.2%). They noted a continual decrease in the proportion of hepatitis A cases in patients younger than 10 years from 41.6% in 2012 to 3.8% in 2018. They noted a slower reduction of reported cases older than 40 years than that of children. The proportion of hepatitis A cases older than 40 years was 27.6% in 2012; this continually raised to 69.2% (164/237) in 2018. Serological investigation results revealed the lowest anti-HAV IgG prevalence (38.6%) in the 0-1.5-year age group, this increased to 75.0% in the 4-6-year age group, covered by this immunization program.