The effectiveness and limitation of the national childhood hepatitis A vaccination program in the Republic of Korea: Findings from the Korean National Health and Nutrition Examination Survey (KNHANES), 2015

Abstract

BackgroundVaccination for hepatitis A virus (HAV) has been implemented as one of the national vaccination programs despite the epidemiological transition of HAV in the Republic of Korea. While the national HAV vaccination program is largely associated with the shift of socioeconomic trend in the country, concerns have been raised on the effectiveness of the HAV immunization. The objective of this study was to examine the epidemiological trend of HAV and assess the effectiveness of the nationwide HAV vaccination policy based on a nationally representative sample of the Korean population collected in 2015.MethodsWe analyzed anti-HAV of 5,856 respondents aged ≥10 years collected from Korean National Health and Nutrition Examination Survey (KNHANES) data in 2015. We estimated age-adjusted anti-HAV prevalence by sociodemographic and other characteristics. We evaluated the factors associated with anti-HAV positivity among each age group (10–19, 20–29, 30–45 and over 45 years old).ResultsThe prevalence of anti-HAV among adults aged ≥10 years was 72.5% (95% confidence interval, CI, 73.7–71.4) in 2015. The lowest age-specific prevalence was among adults aged 20–29 years with 11.9% (95% CI 9.3–15.1%). The prevalence of anti-HAV among those aged 10–14 and 15–19 years was 59.7% (95% CI 52.7–66.4) and 24.0% (95% CI 19.5–29.3), respectively. The prevalence of anti-HAV among adults aged between 30 and 44 years rapidly increased from below 20% to above 90%. The prevalence of anti-HAV among adults aged ≥45 years was 97.8% (95% CI 96.0–97.6). Factors significantly associated with anti-HAV positivity among those aged 10–19 years old were young age, higher house income and high influenza vaccination rate. Compared to the respondents aged 10–19 years (those who were subject to the national childhood vaccine recommendation), those aged 20–29 years (those who were not subject to the recommendation) had low adjusted odds ratio (OR, 0.52 95% CI 0.34–.81 P-value = 0.004) for anti-HAV positivity.ConclusionsThe age-adjusted anti-HAV prevalence showed a U-shaped association, implying the high dependence of anti-HAV prevalence on age and the epidemiological shift. The inclusion of the hepatitis A vaccine into the national immunization recommendation was effective shown by the increase of immunity in the general population. However, the vaccination rate was low in the low-income group. Young adults aged 20–39 years may benefit from inclusion in the HAV vaccination program due to the significantly low vaccination rate.

Causes and countermeasures for repeated outbreaks of hepatitis A among adults in Korea

“…As these cohorts age, the immunity level of Korean adults is likely to decrease [6,7]. According to the results of the 2015 Korea National Health and Nutrition Examination Survey, the seropositivity by age was 12.6% among participants in their 20s, 31.8% among those in their 30s, and 80.3% among those in their 40s, comparable to those in other reports (Table 1) [6,8].…”

“…HAV, hepatitis A virus.1Seroprevalence of anti-HAV was adjusted by area from 2005 to 2009 and by area and sex from 2010 to 2014.2From 2005 to 2009, people over 50 years old presented in groups because of the small numbers and similar seroprevalence.3Overall seroprevalence was adjusted by age, area, and/or sex using the 2010 population.Data sources from: 2005-2014: Kim et al PLoS One 2017;12:e0170432 [6]; 2015: Lim et al PLoS One 2017;12:e0189210 [8]. …”

“…Data sources from: 2005-2014: Kim et al PLoS One 2017;12:e0170432 [6]; 2015: Lim et al PLoS One 2017;12:e0189210 [8]. …”

The Shifting Epidemiology of Hepatitis A in the World Health Organization Western Pacific Region

“…Hepatitis A became a notifiable disease in Korea in 2001. In 1997, hepatitis A vaccination was recommended to children over 12 months as part of the National Immunization Program [ 60 ] and the two-dose regimen is currently included as one of the government-supported vaccines [ 17 ]. Effectiveness of the vaccination program has been supported by the observation of increasing seropositivity in the general population following vaccine introduction; however, there is a low vaccination rate among the low-income groups [ 60 ].…”