Jiseun Lim

The immunogenicity of a single dose of hepatitis A virus vaccines (Havrix® and Epaxal®) in Korean young adults.

Purpose Assessing the immunogenicity of a single dose of hepatitis A virus (HAV) vaccines is important because some people receive only a single dose. However, previous studies have shown variable results and have not examined the effects of demographic characteristics other than gender. This study was performed to examine the immunogenicity of a single dose of HAV vaccine according to the vaccine type and demographic characteristics in young adults. Materials and Methods Seronegative medical school students were randomly allocated to receive either Havrix or Epaxal. Results After approximately 11 months, the seroconversion rate in 451 participants was 80.7%. In men, the Havrix group showed a significantly higher seroconversion rate (81.9%) than the Epaxal group (69.2%), whereas both vaccine groups showed similarly high immunogenicity in women (Havrix: 90.1%, Epaxal: 92.9%; P for interaction=0.062). According to the results of a multivariate analysis, Epaxal showed significantly lower immunogenicity than Havrix only in men. Age, obesity, drinking, smoking, and follow-up time did not significantly affect seroconversion in either gender. Conclusion The seroconversion rate of single-dose HAV vaccines was low in men, particularly in those who received Epaxal. Our results suggest that gender effects should be considered when comparing the immunogenicity of different HAV vaccines.

Seropositivity among Korean Young Adults Approximately 2 Years after a Single-Dose Vaccination against Hepatitis A Virus.

We previously observed 80.7% seropositivity and a significant interaction between gender and hepatitis A virus (HAV) vaccine type (Havrix vs. Epaxal) on the seropositivity approximately 11 months after single-dose HAV vaccinations in Korean young adults. Our objective was to evaluate seropositivity approximately 2 years after a single-dose HAV vaccination and the influence of demographic characteristics on seropositivity, including the interaction between gender and vaccine type. Seronegative medical school students were randomly vaccinated with Havrix or Epaxal. Based on a total serum anti-HAV antibody titer cutoff of 20 IU/mL, 338 participants (76.0%) of the 445 vaccinees were seropositive 20–25 months after a single-dose HAV vaccination. The seropositive rates were similar after vaccination with Havrix (77.0%) and Epaxal (74.9%). Univariate analysis indicated that female (p = 0.052) and less obese (p < 0.001) participants had a higher seropositive rate, whereas other characteristics such as age, alcohol use, smoking history, vaccine type, and follow-up duration were not associated with seropositivity. Multivariate analysis indicated that women (p = 0.026) and participants with moderate alcohol use (p < 0.001) showed significantly higher seropositive rates than men and participants with no or low alcohol use, respectively. The seropositive rates after vaccination with Havrix and Epaxal were 70.9% and 67.5% in men and 87.7% and 91.3% in women, respectively (p for interaction = 0.304). Compared with the seropositive rate approximately 11 months after vaccination, the seropositive rate decreased substantially only in men in the Havrix group (11.0% points), and consequently, the interaction between gender and vaccine type disappeared while seropositivity remained high (87.7% and 91.3% in Havrix and Epaxal groups, respectively) among women approximately 2 years after vaccination. Further studies are needed to assess whether the seropositive rate would be maintained in all groups more than 2 years after a single-dose HAV vaccination.

Evaluation and sensitivity analysis of the effectiveness of unadjuvanted A(H1N1)pdm09 vaccine in hospital workers using multi-center cohort study in Korea

The A(H1N1)pdm09 vaccine was developed and administered to hospital workers at first during the peak of the outbreak in Korea. The present multicenter cohort study was conducted to evaluate whether the A(H1N1)pdm09 vaccine effectively protected hospital workers. The study vaccine contained 15μg of A/California/7/2009 NYMC X-179A(H1N1) without adjuvant, Greenflu-S™. Participants were requested in December 2009 and April 2010 to answer a questionnaire about whether they had been confirmed to be A(H1N1)pdm09 patients based on the real-time reverse transcription-polymerase chain reaction (RT-PCR) assay and had received the A(H1N1)pdm09 vaccine. The vaccination and incidence rates of the A(H1N1)pdm09 were 96.4% (8769/9097), and 0.6% (57/9097), respectively. The crude vaccine effectiveness (VE) was calculated to be 81.8% [95% confidence interval (CI); 61.0-91.5%], while the effectiveness adjusted for hospital, immunization with seasonal trivalent influenza vaccine (TIV) in 2009-10, contact with A(H1N1)pdm09 patients, pre-existing disease, smoking history, and date of follow-up start was 81.9% (95% CI; 52.8-93.1%). When we defined insufficiently immunized cases as unvaccinated, instead of deleting them from the cohort, the adjusted VE increased up to 93.3%. In conclusion, the unadjuvanted monovalent A(H1N1)pdm vaccine was highly protective in hospital workers against laboratory-confirmed A(H1N1)pdm09 infections. VE estimates were sensitive to varying adjustment or assumptions (75.4-93.3%), which suggest the necessity of careful analysis of VE.

Socioeconomic inequalities in health in the context of multimorbidity: A Korean panel study

Socioeconomic inequalities in health are commonly known to decrease at late age. Yet, it remains unclear whether socioeconomic inequalities in health at late age appear in relation to multimorbidity, particularly in Korea where social support remains unsatisfactory for older people. Using three waves of Korea Health Panel, data of 19,942 observations with repeated measure were constructed to ensure a temporal sequence between three socioeconomic measures (i.e., poverty, employment status, and education) and multimorbidity with a t to t+1 year transition. A multilevel multinomial model was applied to quantify the socioeconomic impact across different age, diseases and disease groups, both separately and in combination. There were associations between socioeconomic position (SEP) and multimorbidity, and increasing trends of socioeconomic inequalities not only with greater number of morbidity but also with age. The latter result was only observed with employment status through mid-to-early old age; i.e., between the 40s (odds ratio (OR) = 2.45, 95% confidence interval (CI):1.08–5.57) and 70s (OR = 3.48, 95%CI: 1.24–9.74). The patterns of socioeconomic inequalities in multimorbidity varied for particular pairs of diseases and were stronger in the disease pairs co-occurring with mental and cardiovascular diseases but weaker in the disease pairs co-occurring with cancer. Accumulation of adversity tended to intensify with increase in number of diseases and older age, though this finding was not consistently supported. The labour market should be encouraged to actively participate in actions to promote healthy aging needs to be complemented by the provision of more generous and universal income support to the elderly in Korea.

Risk factors for feelings of sadness and suicide attempts among cancer survivors in South Korea: findings from nationwide cross-sectional study (KNHANES IV–VI)

Introduction As the number of cancer survivors is rapidly increasing with the increased incidence of the disease and improved survival of patients, the prevalence of, and risk factors for, mental health problems and suicidality among cancer survivors should be examined. Methods and analysis Using data obtained from the Korean National Health and Nutrition Examination Survey (2007–2013), we examined 1285 and 33 772 participants who had been and never been diagnosed with cancer, respectively. We investigated the risks of feelings of sadness and suicide attempts among cancer survivors and general population and examined differences in the risks of cancer survivors among subgroups according to cancer-related characteristics. Results The median age of survivors at the time of the survey and at diagnosis was 63 and 54 years, respectively. After adjusting for sex, level of education, household income, occupation, marital status, cancer type, current status of treatment, age at diagnosis and years since diagnosis, the risk of suicide attempts was significantly higher in participants diagnosed with cancer before 45 years of age compared with those diagnosed at 45–64 years (adjusted OR=3.81, 95% CI 1.07 to 13.60, P=0.039), and the higher risk of suicide attempts with borderline significance was found in those for whom more than 10 years had passed since diagnosis compared with those for whom the diagnosis was made only 2–10 years ago (adjusted OR=3.38, 95% CI 0.98 to 11.70, P=0.055). However, feelings of sadness were not significantly associated with any cancer-related characteristic. Conclusion Our results reveal an increased risk of suicide attempts among cancer survivors diagnosed early in life and in those for whom more than 10 years has passed since the diagnosis, suggesting the need for intensive monitoring and support for mental health problems and suicidal risks in this population.

Changing patterns of adult asthma incidence: results from the National Health Insurance Service–National Sample Cohort (NHIS-NSC) database in Korea

This study was conducted to assess the changes in the annual incidence of adult asthma in Korea where the prevalence of asthma had increased steadily in recent decades. A population-based cohort study was conducted using the National Health Insurance Service–National Sample Cohort (NHIS-NSC), which consisted of 746,816 adults aged >20 years between 2004 and 2012. Asthma was defined by two or more physician claims on the basis of a primary diagnostic code for asthma and administration of asthma medications within 1 year. The incidence rates and annual percent change were calculated, and the influence of age and sex on the incidence rates was studied. The annual asthma incidence increased from 3.63 in 2004 to 6.07 per 1,000 person-years in 2008. Since 2008, the asthma incidence did not change significantly. The asthma incidence was higher in women than in men throughout the study periods (p < 0.001) and higher in older than younger age groups (p < 0.001). The asthma incidence did not change in all ages since 2008, except for the 20 s who showed a steady increase. The incidence of asthma in adults reached plateau in Korea, which is consistent with the results from studies in other countries.

The Epidemiological Influence of Climatic Factors on Shigellosis Incidence Rates in Korea

Research has shown the effects of climatic factors on shigellosis; however, no previous study has evaluated climatic effects in regions with a winter seasonality of shigellosis incidence. We examined the effects of temperature and precipitation on shigellosis incidence in Korea from 2002–2010. The incidence of shigellosis was calculated based on data from the Korean Center for Disease Control and Prevention (KCDC, Cheongju, Korea), and a generalized additive model (GAM) was used to analyze the associations between the incidence and climatic factors. The annual incidence rate of shigellosis was 7.9 cases/million persons from 2002–2010. During 2007–2010, high incidence rates and winter seasonality were observed among those aged ≥65 years, but not among lower age groups. Based on the GAM model, the incidence of shigellosis is expected to increase by 13.6% and 2.9% with a temperature increase of 1 °C and a lag of two weeks and with a mean precipitation increase of 1 mm and a lag of five weeks after adjustment for seasonality, respectively. This study suggests that the incidence of shigellosis will increase with global climate change despite the winter seasonality of shigellosis in Korea. Public health action is needed to prevent the increase of shigellosis incidence associated with climate variations.

Age, Period, and Cohort Effects on Suicide Mortality in South Korea, 1992–2015

Although the effects of age, period, and cohort (APC) on suicide are important, previous work in this area may have been invalid because of an identification problem. We analyzed these effects under three different scenarios to identify vulnerable groups and thus overcame the identification problem. We extracted the annual numbers of suicides from the National Death Register of Korea (1992–2015) and estimated the APC effects. The annual average suicide rates in 1992–2015 were 31.5 and 14.7 per 100,000 males and females, respectively. The APC effects on suicide were similar in both sexes. The age effect was clearly higher in older subjects, in contrast to the minimal changes apparent during earlier adulthood. The birth cohort effect showed an inverted U shape; a higher cohort effect was evident in females born in the early 1980s when period drift was larger than 3.7%/year. Period effect increased sharply during the early 1990s and 2000s. We found that elderly and young females may be at a particularly high risk of suicide in Korea.

Differentiation of direct and indirect socioeconomic effects on suicide attempts in South Korea

Abstract Despite the wide recognition of the inverse association between socioeconomic position (SEP) and suicidal behaviors, its underlying process and potential mediators are little known. This study investigated the pathway from SEP to suicide attempts with attention to potential mediators. From the Korean Health and Nutrition Examination Survey 2007–2013, which is a nationwide cross-sectional survey of the health and nutritional status, a total of 34,565 participants (≥30 years) were included in the analysis. To unfold the pathways linking SEP to suicide attempts, the direct and indirect effects of 3 SEP measures (educational attainment, household income, and occupational group) and 3 mediators (physical illness, mental health problems, and problematic drinking) were differentiated using structured equation model (SEM). Most of direct and indirect effects of educational attainment, household income, and occupational group on suicide attempts were significant; Nonemployment status had the largest total (&bgr; = 0.291, P < .01) and direct effects (&bgr; = 0.212, P < .01), while educational attainment had the largest indirect effect (&bgr; = −0.124, P < .01). Educational attainment was mainly mediated by physical illness and problem drinking, whereas household income and occupational group were mainly mediated by anxious or depressed mood and problem drinking. Physical illness played a major role in explaining suicide attempts, compared to mental health problem and problem drinking. Overall, experience of socioeconomic disadvantage increased suicide attempts independently of mental and physical problems. An extension of suicide prevention program is required for comprehensively targeting people with general problems such as physical illness and low SEP, complemented to narrowly targeting high risk group with, such as mental health problem.