Comparison of the immunogenicity and safety of 3 inactivated hepatitis A vaccines in Korean children aged 12 to 18 months: An open-label, randomized, prospective, multicenter study

Several approved inactivated hepatitis A (HA) vaccines are available in Korea. These have been shown to be immunogenic and safe in European children; however, their immunogenicity and safety have not been investigated among Korean children. We aimed to compare the immunogenicity and safety of the most commonly used HA vaccines in ethnic Korean children aged 12 to 18 months.In this open-label, randomized, prospective, multicenter study, 108 children were enrolled and randomized to receive a pediatric form of Avaxim, Epaxal, or Havrix. The 2nd dose was administered after an interval of 6 months. Anti-HA virus (HAV) immunoglobulin (Ig) G was measured to assess geometric mean concentrations (GMCs) and seropositvity rates (≥20 mIU/mL anti-HAV IgG). To assess safety, local solicited adverse events (AEs), systemic solicited AEs, unsolicited AEs, and serious AEs (SAEs) were graded.Among the 108 participants enrolled, 37, 34, and 37 received Avaxim, Epaxal, and Havrix, respectively. After administration of 2 doses, the seropositivity rates in the Avaxim, Epaxal, and Havrix groups were all 100% (95% confidence intervals [CIs]: 99.0-100, 98.9-100, and 99.0-100, respectively; P < .001). The anti-HAV GMCs in the Avaxim, Epaxal, and Havrix groups were 5868.4 (95% CI: 4237.2-8126.6), 1962.1 (95% CI: 1298.0-2965.9), and 2232.9 mIU/mL (95% CI: 1428.4-3490.4), respectively, after administration of 2 doses (P < .001). There were no significant differences in the proportions of participants reporting local solicited AEs, systemic solicited AEs, unsolicited AEs, and SAEs among the 3 vaccine groups after the 1st and 2nd doses. All local solicited and unsolicited AEs were grade 1 or 2. Grade 3 systemic solicited AE occurred in 5.4% and 2.9% of the participants in the Havrix group after the 1st and 2nd doses, respectively. SAEs after the 1st and 2nd doses were reported in 2 participants and 1 participant, respectively, but none was assessed as being related to vaccination.The results indicate that these vaccines were safe and immunogenic in ethnic Korean children. The results have contributed to the establishing of an HA vaccination policy in Korea and will be informative to countries that plan to initiate vaccination programs against HAV.

A waterborne outbreak involving hepatitis A virus genotype IA at a residential facility in the Republic of Korea in 2015

BACKGROUND

Hepatitis A virus (HAV), a major cause of acute hepatitis, has had the highest occurrence among group 1 nationally notifiable infectious diseases in Korea since 2010.Recently,the annual increase in the HAV infection rate among young adults has become a public health concern.

OBJECTIVES

The aim of this study was to describe an outbreak of acute hepatitis in a residential facility in April 2015 and to identify potential sources of this outbreak.

STUDY DESIGN

Sera from all exposed residents were tested for anti-HAV IgM or IgG antibodies by ELISA. Clinical (sera and stool) and environmental samples were screened for the presence of HAV RNA using one-step RT-PCR and nested PCR. The VP3-VP1 regions of HAV were analyzed using the BLAST database and MEGA7 software.

RESULTS

Of the 82 persons in the facility, 12 (14.6%, including 10 residents and 2 health care workers) were diagnosed with hepatitis A. Clinical symptoms were evident in 9 individuals, one of whom died, and the remaining four patients were asymptomatic. Traceback investigation revealed that HAV-RNA (genotype IA) was detected in the patients' stools and the groundwater used in the facility.

CONCLUSIONS

We described an HAV outbreak in a facility for the disabled due to using a water supply that was mixed with contaminated groundwater. Therefore, HAV vaccination and periodic water inspections in group facilities should be emphasized to prevent HAV infection.

Nationwide Seropositivity of Hepatitis A in Republic of Korea from 2005 to 2014, before and after the Outbreak Peak in 2009

Background/Aims

The epidemiologic shift of hepatitis A virus (HAV) infection in the South Korean population resulted in a peak outbreak of hepatitis in 2009. The aim of this study was to clarify the seropositivity of anti-HAV antibody (anti-HAV) and its demographic characteristics before and after the peak outbreak from 2005 to 2014.

Methods

This retrospective study analyzed the anti-HAV data of all individuals from 1,795 medical institutions referred to a major central laboratory from January 2005 through December 2014, as a sentineal tool for monitoring annual variation of anti-HAV positivity. The prevalence of anti-HAV was adjusted for age and area with the standard population based on the 2010 Census data.

Results

A total of 424,245 individuals were included in this study. The overall age-adjusted anti-HAV prevalence decreased from 65.6% in 2005 to 62.2% in 2014. During the 10-year period, the seroprevalence continuously decreased in persons aged 30 to 39 years (69.6% to 32.4%) and those aged 40 to 49 years (97.9% to 79.3%) due to the cohort effect. In contrast, it increased in persons aged 10 to 19 years (15.4% to 35.2%), while it was the lowest (8.7%) in 2010 before rebounding to 20.2% in 2014 in persons aged 20 to 29 years due to a vaccination effect.

Conclusion

Although the HAV vaccination rate increased, the anti-HAV seropositivity in South Korea decreased from 65.6% to 62.2% in this study population. In particular, the immunity of young adults was still low, and an outbreak of HAV is possible in the near future. Therefore, continuous monitoring and optimal preventive measures to prevent future outbreaks should be considered.

Hepatitis A in Korea from 2011 to 2013: Current Epidemiologic Status and Regional Distribution

The hepatitis A virus (HAV) has been the leading cause of viral hepatitis in Korea since the 2000s. We aimed to describe the current status and regional differences in hepatitis A incidence. We studied the total number of hepatitis A cases reported to the Korea Centers for Disease Control and Prevention through the National Infectious Diseases Surveillance System between 2011 and 2013. Additionally, National Health Insurance Review and Assessment Service data and national population data from Statistics Korea were used. In total, 7,585 hepatitis A cases were reported; 5,521 (10.9 cases per 100,000 populations), 1,197 (2.3 cases per 100,000 populations), and 867 (1.7 cases per 100,000 populations) in 2011, 2012, and 2013, respectively. Fifty-eight patients were infected outside of the country and 7,527 patients represented autochthonous HAV infection cases. Autochthonous HAV infection occurred more frequently among men than women (4,619 cases, 6.1 cases per 100,000 population vs. 2,908 cases, 3.9 cases per 100,000 population). The incidence rate was higher in the 20-29 yr-old group (2,309 cases, 11.6 cases per 100,000 populations) and 30-39 yr-old group (3,306 cases, 13.6 cases per 100,000 populations). The majority of cases were reported from March to June (53.6%, 4,038/7,527). Geographic analyses revealed a consistently high relative risk (RR) of HAV infection in mid-western regions (2011, RR, 1.25, P=0.019; 2012, RR, 2.53, P<0.001; 2013, RR, 1.86, P<0.001). In summary, we report that hepatitis A incidence has been decreasing gradually from 2011 to 2013 and that some regions show the highest prevalence rates of HAV infection in Korea.

Reappraisal of the Immunogenicity and Safety of Three Hepatitis A Vaccines in Adolescents

Although the overall incidence of hepatitis A in Korea has been decreasing, adolescents remain highly vulnerable to its outbreaks. This study was conducted to compare the immunogenicity and safety of three hepatitis A vaccines in Korean adolescents. Healthy anti-hepatitis A virus seronegative subjects aged 13 to 19 yr were randomized in three equal groups to receive two doses of Avaxim™, Epaxal®, or Havrix®, 6 to 12 months apart. Seroconversion rates one month after the first dose were 98%, 95%, and 93% for Avaxim™, Epaxal®, and Havrix®, respectively. Seroconversion rates reached 100% for all vaccine groups one month after the second dose. Anti-HAV geometric mean concentrations (GMCs) were 7,207.7 mIU/mL (95% CI, 6023.1-8684.7), 1,750.5 mIU/mL (95% CI, 1362.9-2248.3), and 1,953.5 mIU/mL (95% CI, 1459.4-2614.7) after two doses of Avaxim™, Epaxal®, and Havrix® respectively. Avaxim™ was significantly more immunogenic than Epaxal® and Havrix®, whereas there were no significant differences in antibody responses between Epaxal® and Havrix®. Local and systemic solicited adverse events (AEs) were mostly of mild-to-moderate intensity and resolved within 5 days. No serious AEs were reported. In conclusion, all three vaccines are highly immunogenic and well-tolerated in Korean adolescents. (Clinical Trial Registry NCT00483470).

The Economic Burden of Hepatitis A, B, and C in South Korea

The prevalence of hepatitis in South Korea is relatively high compared to that in other high-income countries. For this reason, viral hepatitis infection not only affects the population's health, but also impacts national healthcare costs. This study was performed in order to estimate the individual economic costs of the hepatitis A, B, and C viruses as well as to determine, using nationally representative data, the trends in South Korea with respect to these viruses during the 2008-2011 period. The study found that the prevalence of hepatitis A had decreased, but those of hepatitis B and C had increased overall. The mortality rate of hepatitis C was higher than that of the other two types. The mortality rate of hepatitis B had changed little, whereas that of hepatitis C had risen. The total cost of hepatitis A had decreased, from US $62.2 million to US $45.7 million, although a notable exception occurred in 2009, when the cost was US $126.6 million. Conversely, the total cost of hepatitis B had increased rapidly during the same period, from US $501.4 million to US $607.8 million. Finally, the total cost of hepatitis C had also increased from US $63.9 million to US $90.7 million. The direct costs of hepatitis A, B, and C were estimated to account for approximately 35.5%, 46.6%, and 58.0% of the total, respectively. These findings demonstrate the economic burden associated with hepatitis A, B, and C, and demonstrate the need to establish an effective prevention and management policy for future planning in South Korea.

Public acceptance and willingness to hepatitis a vaccination in children aged 7-18 years in Republic of Korea

Hepatitis A can cause serious illness among adolescents and adults with low vaccination coverage. Even though hepatitis A vaccine is one of the strong candidates for Korean national immunization program, adolescents aged older than 12 yr would not benefit. Our purpose was to assess the willingness and analyze the correlates of Korean mothers for hepatitis A (HepA) vaccination to develop strategies for HepA vaccination. A national telephone survey on 800 mothers with children aged 7-18 yr was conducted with random-digit dialing method. Sixty-two percent and 92% of the mothers reported that they were willing to HepA vaccination at current cost and at half of the current cost, respectively. However, at current cost, only 79% wished to vaccinate their child in an epidemic and 32% wished to vaccinate promptly. Having two or more children, not having future plans to send the child overseas, and low family income were significantly associated with not willing to HepA vaccination. Low perception of the susceptibility for hepatitis A and perception of the current cost as barrier increased the odds of unwillingness to vaccination at current cost and to prompt vaccination. The mothers' willingness to HepA vaccination for the children aged 7-18 yr in Korea was not very high at current cost and associated socioeconomic status and health-belief. Targeted intervention or strategies are needed to increase the HepA vaccination rate among children in Korea.

Changes in the seroprevalence of IgG anti-hepatitis A virus between 2001 and 2013: experience at a single center in Korea

Background/Aims

The incidence of symptomatic hepatitis A reportedly increased among 20- to 40-year-old Korean during the late 2000s. Vaccination against hepatitis A was commenced in the late 1990s and was extended to children aged <10 years. In the present study we analyzed the changes in the seroprevalence of IgG anti-hepatitis A virus (HAV) over the past 13 years.

Methods

Overall, 4903 subjects who visited our hospital between January 2001 and December 2013 were studied. The seroprevalence of IgG anti-HAV was analyzed according to age and sex. In addition, the seroprevalence of IgG anti-HAV was compared among 12 age groups and among the following time periods: early 2000s (2001-2003), mid-to-late 2000s (2006-2008), and early 2010s (2011-2013). The chi-square test for trend was used for statistical analysis.

Results

The seroprevalence of IgG anti-HAV did not differ significantly between the sexes. Furthermore, compared to the seroprevalence of IgG anti-HAV in the early 2000s and mid-to-late 2000s, that in the early 2010s was markedly increased among individuals aged 1-14 years and decreased among those aged 25-44 years (P<0.01). We also found that the seroprevalence of IgG anti-HAV in individuals aged 25-44 years in the early 2010s was lower than that in the early 2000s and mid-to-late 2000s.

Conclusions

The number of symptomatic HAV infection cases in Korea is decreasing, but the seroprevalence of IgG anti-HAV is low in the active population.

Clinical characteristics and outcomes of acute hepatitis a in Korea: a nationwide multicenter study

The aim of this study was to investigate the clinical characteristics of acute hepatitis A during a recent outbreak in Korea. Data of patients diagnosed with acute hepatitis A from 2007 to 2009 were collected from 21 tertiary hospitals retrospectively. Their demographic, clinical, and serological characteristics and their clinical outcomes were analyzed. A total of 4,218 patients (mean age 33.3 yr) were included. The median duration of admission was 9 days. The mean of the highest ALT level was 2,963 IU/L, total bilirubin was 7.3 mg/dL, prothrombin time INR was 1.3. HBsAg was positive in 3.7%, and anti-HCV positive in 0.7%. Renal insufficiency occurred in 2.7%, hepatic failure in 0.9%, relapsing hepatitis in 0.7%, and cholestatic hepatitis in 1.9% of the patients. Nineteen patients (0.45%) died or were transplanted. Complications of renal failure or prolonged cholestasis were more frequent in patients older than 30 yr. In conclusion, most patients with acute hepatitis A recover uneventfully, however, complication rates are higher in patients older than 30 yr than younger patients. Preventive strategies including universal vaccination in infants and active immunization of hepatitis A to adult population should be considered for prevention of community-wide outbreaks of hepatitis A in Korea.

Abnormality on liver function test

Children with abnormal liver function can often be seen in outpatient clinics or inpatients wards. Most of them have respiratory disease, or gastroenteritis by virus infection, accompanying fever. Occasionally, hepatitis by the viruses causing systemic infection may occur, and screening tests are required. In patients with jaundice, the tests for differential diagnosis and appropriate treatment are important. In the case of a child with hepatitis B virus infection vertically from a hepatitis B surface antigen positive mother, the importance of the recognition of immune clearance can't be overstressed, for the decision of time to begin treatment. Early diagnosis changes the fate of a child with Wilson disease. So, screening test for the disease should not be omitted. Non-alcoholic fatty liver disease, which is mainly discovered in obese children, is a new strong candidate triggering abnormal liver function. Muscular dystrophy is a representative disease mimicking liver dysfunction. Although muscular dystrophy is a progressive disorder, and early diagnosis can't change the fate of patients, it will be better to avoid parent's blame for delayed diagnosis.

Low level of immunity against hepatitis A among Korean adolescents: vaccination rate and related factors

BACKGROUND

We evaluated the current vaccination rate and immunity in the Korean adolescent population and analyzed their parents' attitudes toward hepatitis A virus (HAV) vaccination.

METHODS

Between March and April 2011, sera were collected for immunoglobulin (Ig) G anti-HAV testing from students in their first year of high school from 12 different high schools located in southwestern Seoul. Simultaneously, questionnaires were given to the parents of the students to evaluate factors related to HAV vaccination, including demographics, HAV vaccination status, reason for getting the vaccination, and awareness regarding HAV.

RESULTS

Sera from 2,879 subjects and questionnaires from their parents were collected. The HAV vaccination rate among adolescents aged between 14 and 17 years was 18.9%, and the seroprevalence was 15.4%. Among subjects who reported receiving the HAV vaccination, the IgG anti-HAV seropositivity rate was only 42.2%. For subjects who were not vaccinated, the IgG anti-HAV seropositivity rate was 9.1%. The most significant reason for receiving the vaccination was recommendation from health care providers; the most important source of information regarding the vaccination was public health organizations.

CONCLUSION

HAV vaccination rate and anti-HAV seroprevalence in Korean adolescents was low; the seropositivity rate in the vaccinated group was lower than expected. Actively recommending HAV vaccination in this group is required, and routine, nationwide, government-sponsored vaccination of adolescents against HAV should be considered.

Full-length genomic sequence of subgenotype IIIA hepatitis A virus isolate in Republic of Korea

Hepatitis A virus is known to cause acute hepatitis and has significant implications for public health throughout the world. In the Republic of Korea, the number of patients with hepatitis A virus infection has been increasing rapidly since 2006. In this study, the Kor-HAV-F strain was identified as subgenotype IIIA by RT-PCR, and its identity was confirmed by nucleotide sequencing and alignment analysis. Moreover, detailed phylogenetic analysis indicated that the Kor-HAV-F strain clustered into subgenotype IIIA, including strains isolated in Japan, Norway, and India. The entire amino acid sequence of the VP1 and 2A regions was compared with that of the reference strains isolated in various countries. We found 2 amino acid changes (T168A and L96P, resp.) in the VP1 and 2A regions, which had not been found in any other hepatitis A virus strain. To our knowledge, this study is the first to report the full-length sequence of a hepatitis A virus isolated in the Republic of Korea.

Risk factors for acute hepatitis A infection in Korea in 2007 and 2009: a case-control study

This study aimed to identify the risk factors associated with acute hepatitis A virus (HAV) infection in the Korean population. Participants were recruited from five referral hospitals across the country in 2007 and from 11 hospitals in 2009. Patients with positive anti-HAV IgM antibody tests became the case group, while patients treated for non-contagious diseases at the same hospitals were recruited as controls. A total of 222 and 548 case-control pairs were studied in the 2007 and 2009 surveys, respectively. Data from the surveys were analyzed jointly. In a multivariate analysis, sharing the household with HAV-infected family members (OR, 6.32; 95% CI, 1.4-29.6), contact with other HAV-infected individuals (OR, 4.73; 95% CI, 2.4-9.4), overseas travel in 2007 (OR, 19.93; 95% CI, 2.3-174.4), consumption of raw shellfish (OR, 2.51; 95% CI, 1.8-3.5), drinking bottled water (OR, 1.64; 95% CI, 1.3-8.4), and occupation that involve handling food (OR, 3.30; 95% CI, 1.3-8.4) increased the risk of HAV infection. Avoiding contact with HAV-infected individuals and avoiding raw foods eating could help minimize the risk of hepatitis A infection. Immunization must be beneficial to individuals who handle food ingredients occupationally or travel overseas to HAV-endemic areas.

Epidemiological changes in hepatitis A in Korea: increasing age and its effect on clinical outcomes

Korea has recently experienced an increasing number of acute hepatitis A cases. We investigated the dynamics of hepatitis A and changes in the mean age of patients in a hospital in Seoul, Korea. Mean age increased consistently from 19 years in 1996 to 30 years in 2009 (P < 0·0001). Between two acute hepatitis A outbreaks in 1998–1999 and in 2008–2009, mean age increased from 23 to 30 years (P < 0·001). However, the hepatitis A clinical outcomes were similar between the outbreaks. Duration of hospital stay, creatinine level and prothrombin time did not differ. Throughout the study period, individuals born in the 1970s and 1980s comprised the largest proportion (84%) of patients. As this susceptible generation ages, the mean age of hepatitis A patients in Korea will increase consistently. However, at present, the impact of increasing age on clinical outcomes is not apparent.

Infectious diseases in children and adolescents in the Republic of Korea; Past & recent status

Compared to the past decades, in recent decades, environmental and hygienic conditions in the Republic of Korea have improved along with socioeconomic developments, and the incidence of most infectious diseases, especially vaccine-preventable diseases, has greatly decreased due to active immunization with the developed level of health care. However, the incidence of some diseases has been increasing, and new diseases have been emerging. To cope with such changes actively, the government put the "Law for Control and Prevention of Infectious Diseases" into effect; this law was entirely revised on December 30, 2010. In this report, I review the past and recent status of infectious diseases in the Republic of Korea, following the introduction of this law, on the basis of data in the "National Notifiable Disease Surveillance System", which had been accumulated between the years 1960 and 2010.

Prevalence of IgG anti-HAV in patients with chronic hepatitis B and in the general healthy population in Korea

Background/Aims

Few studies have investigated hepatitis A virus (HAV) seroepidemiology in Koreans with chronic liver disease (CLD). This study compared the prevalence of IgG anti-HAV between the general healthy population and patients with hepatitis B virus-related CLD (HBV-CLD), with the aim of identifying predictors of HAV prior exposure.

Methods

In total, 1,319 patients were recruited between June 2008 and April 2010. All patients were tested for IgG anti-HAV, hepatitis B surface antigen (HBsAg), and antibodies to hepatitis C virus. The patients were divided into the general healthy population group and the HBV-CLD group based on the presence of HBsAg. The seroprevalence of IgG anti-HAV was compared between these two groups.

Results

The age-standardized seroprevalence rates of IgG anti-HAV in the general healthy population and patients with HBV-CLD were 52.5% and 49.1%, respectively. The age-stratified IgG anti-HAV seroprevalence rates for ages ≤19, 20-29, 30-39, 40-49, 50-59, and ≥60 years were 14.3%, 11.2%, 45.5%, 90.5%, 97.6% and 98.3%, respectively, in the general healthy population, and 0%, 9.8%, 46.3%, 91.1%, 97.7%, and 100% in the HBV-CLD group. In multivariate analysis, age (<30 vs. 30-59 years: OR=19.339, 95% CI=12.504-29.911, P<0.001; <30 vs. ≥60 years: OR=1060.5, 95% CI=142.233-7907.964, P<0.001) and advanced status of HBV-CLD (OR=19.180, 95% CI=4.550-80.856, P<0.001) were independent predictors of HAV prior exposure.

Conclusions

The seroprevalence of IgG anti-HAV did not differ significantly between the general-healthy-population and HBV-CLD groups. An HAV vaccination strategy might be warranted in people younger than 35 years, especially in patients with HBV-CLD.

Seroepidemiology of hepatitis A in Korea: changes over the past 30 years

This study aimed to assess the immune status of the Korean population against hepatitis A virus (HAV). Residual serum samples from 2008 to 2010 were collected from diagnostic laboratories and a total of 1,872 samples were analyzed. Anti-HAV seroprevalence was 57.3% in subjects aged 1-4 yr, 69.8% at 5-9 yr and decreased to 38.8% at 10-14 yr, 13.0% at 15-19 yr, and 11.7% at 20-29 yr. Seroprevalence increased with increasing age: 52.2% at 30-39 yr, 83.2% at 40-49 yr, 81.4% at 50-59 yr, 93.2% at 60-69 yr, and 95.1% at 70-79 yr. The most susceptible age group consisted of subjects aged 10-29 yr, especially those aged 20-29 yr. This pattern is markedly different from that in the past 3 decades, where the most susceptible group had consisted of children aged less than 10 yr and almost all subjects aged more than 20 yr had developed anti-HAV antibodies. Because of improvements in hygiene and introduction of hepatitis A vaccine, the age demographic of the susceptible population has shifted. These data are important for creating new prevention measures, including vaccination policies, to prevent and control outbreaks of hepatitis A in Korea.

[An epidemiological analysis of hepatitis A virus serologic markers during the recent four years in Korea]

BACKGROUND

To establish effective preventive measures for hepatitis A virus (HAV) infection, a nationwide epidemiologic study on seroprevalence of anti-HAV and the disease prevalence is needed. The aim of this study was to analyze the recent sero-epidemiological changes of hepatitis A markers in Korea.

METHODS

The results of 11,068 anti-HAV total and 32,360 anti-HAV IgM tests by electro-chemiluminescence immunoassay (ECLIA) that had been requested in recent four years (2005-2008) to a reference medical laboratory from 1,699 institutions nationwide were retrospectively analyzed according to the distribution of year, sex, and age groups.

RESULTS

The overall positive rate of anti-HAV total was 62.8%. The overall positive rate of anti-HAV IgM was 11.0%, showing a significantly increasing trend by year: 7.7%, 10.9%, 8.9%, and 14.3% in 2005, 2006, 2007, and 2008, respectively (P<0.0001). The positive rate of anti-HAV IgM was higher in male than in female subjects (11.8% vs 10.0%, P<0.0001), and 81.8% (2,916/3,566) of the anti-HAV IgM positive results were observed in the age groups of 21-40 yr. The annual positive rates of anti-HAV total and anti-HAV IgM showed significantly decreasing and increasing trends, respectively, in the age groups of > or = 21 yr.

CONCLUSION

In accordance with a decreasing sero-positivity of anti-HAV total, the prevalence of acute hepatitis A virus infection has been considerably increased during the recent four years in the age groups of > or = 21 yr. The results of this study could be used effectively as a basic data for establishing effective preventive measures for hepatitis A including vaccination in these susceptible age groups.

Hepatitis A Vaccination Rates and Related Factors in a 2005 Population-based Study in Nonsan, Korea

OBJECTIVES

The incidence of clinical hepatitis A has increased in young Korean adults since the mid-1990s. Although hepatitis A vaccinations have been administered in private clinics over the past 10 yr, no data exist on the vaccination rate and relating factors.

METHODS

In 2005, a population-based survey of 12-35-month-old children was carried out in Nonsan, Korea. An interview survey was completed for 71.3% of the children. All data came from a vaccination card or confirmation from a provider.

RESULTS

The hepatitis A vaccination rate was 42.3% for ≥1 dose and 24.7% for 2-dose. The results of the multivariate regression analysis for the hepatitis A vaccination showed that the second (OR=1.6) and third and successive children (OR=3.3) were less often immunized than the first child. Low economic status (OR=1.6), rural area (OR=1.5) and employed mother (OR=1.5) were also correlated with a lower vaccination rate. The hepatitis A vaccination rate was significantly lower in children who had no other vaccinations: measlesmumps-rubella (OR=2.8 for ≥1 dose and 7.3 for 2-dose), varicella (OR=20.2 and 22.0, respectively) and Haemophilus influenza type b (OR=14.3 and 13.3, respectively).

CONCLUSION

To prevent outbreaks of clinical hepatitis A by enough herd immunity, a vaccination should be included in the National Immunization Program and a vaccination policy developed and implemented that can overcome the barriers to immunization such as late birth order and a mother's employment.