Difference in seroprevalence of IgG antibodies against hepatitis A virus on general population in 1998 and 2019 in Iwate Prefecture, Japan
Background: Hepatitis A virus (HAV) infection, a sporadically occurring disease in general populations, is a major cause of acute hepatitis, but rarely causes death. It is important to know the current situation regarding this infection rate among the general population so that an effective strategy and action plan for HAV vaccination or treatment can be established. Here, we investigated the seroprevalence of IgG antibodies against HAV (anti-HAV) in Iwate Prefecture, Japan, in 1998 and 2019,
... in 1998 and 2019, and compared the seroprevalence patterns over these past two decades. Methods: Altogether, 777 randomly selected serum samples were obtained from health check-up residents in Iwate prefecture in 1998 and 2019. Serum anti-HAV IgG levels were measured by radioimmunoassay (in 1998) and chemiluminescent immunoassay (in 2019). Results: Altogether, 586 serum samples (278 from males, 308 from females; mean age 53 years; range 30–89 years) and 191 serum samples (96 from males, 95 from females; mean age 54 years; range 30–89 years) from 1998 and 2019 were tested, respectively. The overall anti-HAV IgG prevalence in 2019 [16.8% (95% confidence interval, CI; 1.8–22.8%)] was significantly lower than that in 1998 [47.8% (95% CI 43.7–51.9%)] (p<0.001). Subgroup analysis of each age group showed that the anti-HAV IgG prevalence tended to be low in the young, increased with age, and each age group's prevalence became older across the two decades. The anti-HAV IgG prevalence for those older than 50 years in 2019 [28.1% (95% CI 11.8–22.8%)] was significantly lower than that in 1998 [75.6% (95% CI 43.7–51.9%)] (p<0.001). Conclusions: A shift toward older across in anti-HA IgG prevalence was observed from 1998 to 2019, revealing that the younger population lacks immunity to HAV. Thus, selective HAV vaccination might be necessary for prevent severe HAV infection.