Waning Effectiveness of One-dose Universal Varicella Vaccination in Korea, 2011–2018: a Propensity Score Matched National Population Cohort

Background@#Despite high coverage (~98%) of universal varicella vaccination (UVV) in the Republic of Korea since 2005, reduction in the incidence rate of varicella is not obvious.The study aimed to evaluate the vaccine effectiveness (VE) of one-dose UVV by timeline and severity of the disease. @*Methods@#All children born in Korea in 2011 were included for this retrospective cohort study that analyzed insurance claims data from 2011–2018 and the varicella vaccination records in the immunization registry. Adjusted hazard ratios by Cox proportional hazard models were used to estimate the VE through propensity score matching by the month of birth, sex, healthcare utilization rate, and region. @*Results@#Of the total 421,070 newborns in the 2011 birth cohort, 13,360 were matched for age, sex, healthcare utilization rate, and region by the propensity score matching method. A total of 55,940 (13.29%) children were diagnosed with varicella, with the incidence rate 24.2 per 1000 person-year; 13.4% of vaccinated children and 10.4% of unvaccinated children. The VE of one-dose UVV against any varicella was 86.1% (95% confidence interval [CI], 81.4–89.5) during the first year after vaccination and 49.9% (95% CI, 43.3–55.7) during the 6-year followup period since vaccination, resulting in a 7.2% annual decrease of VE. The overall VE for severe varicella was 66.3%. The VE of two-dose compared to one-dose was 73.4% (95% CI, 72.2–74.6). @*Conclusion@#We found lower long-term VE in one-dose vaccination and waning of effectiveness over time. Longer follow ups of the vaccinated children as well as appropriately designed studies are needed to establish the optimal strategy in preventing varicella in Korea.

Waning Effectiveness of One-dose Universal Varicella Vaccination in Korea, 2011–2018: a Propensity Score Matched National Population Cohort

Background@#Despite high coverage (~98%) of universal varicella vaccination (UVV) in the Republic of Korea since 2005, reduction in the incidence rate of varicella is not obvious.The study aimed to evaluate the vaccine effectiveness (VE) of one-dose UVV by timeline and severity of the disease. @*Methods@#All children born in Korea in 2011 were included for this retrospective cohort study that analyzed insurance claims data from 2011–2018 and the varicella vaccination records in the immunization registry. Adjusted hazard ratios by Cox proportional hazard models were used to estimate the VE through propensity score matching by the month of birth, sex, healthcare utilization rate, and region. @*Results@#Of the total 421,070 newborns in the 2011 birth cohort, 13,360 were matched for age, sex, healthcare utilization rate, and region by the propensity score matching method. A total of 55,940 (13.29%) children were diagnosed with varicella, with the incidence rate 24.2 per 1000 person-year; 13.4% of vaccinated children and 10.4% of unvaccinated children. The VE of one-dose UVV against any varicella was 86.1% (95% confidence interval [CI], 81.4–89.5) during the first year after vaccination and 49.9% (95% CI, 43.3–55.7) during the 6-year followup period since vaccination, resulting in a 7.2% annual decrease of VE. The overall VE for severe varicella was 66.3%. The VE of two-dose compared to one-dose was 73.4% (95% CI, 72.2–74.6). @*Conclusion@#We found lower long-term VE in one-dose vaccination and waning of effectiveness over time. Longer follow ups of the vaccinated children as well as appropriately designed studies are needed to establish the optimal strategy in preventing varicella in Korea.

Erratum: Addition of a Co-Author: Etiology of Invasive Bacterial Infections in Immunocompetent Children in Korea (2006–2010): a Retrospective Multicenter Study

The authors regret that one co-author (Kyung-Hyo Kim) was missing in the article.

Etiology of Invasive Bacterial Infections in Immunocompetent Children in Korea (2006–2010): a Retrospective Multicenter Study

BACKGROUND: Invasive bacterial infections in apparently immunocompetent children were retrospectively analyzed to figure causative bacterial organisms in Korea. METHODS: A total of 947 cases from 25 university hospitals were identified from 2006 to 2010 as a continuance of a previous 10-year period study from 1996 to 2005. RESULTS: Escherichia coli (41.3%), Streptococcus agalactiae (27.7%), and Staphylococcus aureus (27.1%) were the most common pathogens in infants < 3 months of age. S. agalactiae was the most prevalent cause of meningitis and pneumonia and E. coli was the major cause of bacteremia without localizing signs in this group. In children 3 to 59 months of age, Streptococcus pneumoniae (54.2%), S. aureus (20.5%), and Salmonella spp. (14.4%) were the most common pathogens. S. pneumoniae was the leading cause of pneumonia (86.0%), meningitis (65.0%), and bacteremia without localizing signs (49.0%) in this group. In children ≥ 5 years of age, S. aureus (62.8%) was the predominant pathogen, followed by Salmonella species (12.4%) and S. pneumoniae (11.5%). Salmonella species (43.0%) was the most common cause of bacteremia without localizing signs in this group. The relative proportion of S. aureus increased significantly over the 15-year period (1996–2010) in children ≥ 3 months of age (P < 0.001), while that of Haemophilus influenzae decreased significantly in both < 3 months of age group (P = 0.036) and ≥ 3 months of age groups (P < 0.001). CONCLUSION: S. agalactiae, E. coli, S. pneumoniae, and S. aureus are common etiologic agents of invasive bacterial infections in Korean children.

Factors associated with mumps meningitis and the possible impact of vaccination / 소아과

PURPOSE: Mumps meningitis is a common complication of mumps infection; however, information on mumps meningitis in the postvaccine era is limited. The purpose of the present study was to determine factors associated with mumps meningitis and to discuss the effect of vaccination on this disease. METHODS: We retrospectively reviewed patients younger than 19 years with mumps, diagnosed at a university hospital in Korea between 2003 and 2013. Patients were divided into groups with and without meningitis, and the clinical features of the 2 groups were compared. RESULTS: The study enrolled 119 patients: 19 patients with meningitis and 100 patients without. Univariate analysis showed that older age (median: 15 years vs. 9.5 years, respectively), a longer interval from last vaccination (median: 10.2 years vs. 4.8 years, respectively), and febrile presentation (94.7% vs. 31.0%, respectively) were significantly associated with mumps meningitis. Sex, number of vaccination doses, bilateral parotitis, and the presence of complications other than meningitis did not differ between the 2 groups. In multivariate logistic regression analysis, age (odds ratio, 1.38; 95% confidence interval, 1.01-1.89; P=0.04) and fever (odds ratio, 30.46; 95% confidence interval, 3.27-283.61; P<0.01) remained independent factors for mumps meningitis. CONCLUSION: Clinicians in the postvaccine era should be aware of the possibility of mumps meningitis in febrile cases of mumps in adolescents, regardless of the number of vaccination doses. To establish the role of vaccination in mumps meningitis, further studies will be necessary.

Helicobacter pylori Infection and Intestinal Metaplasia among Healthy Adolescents

BACKGROUND/AIMS: The purpose of our study was to investigate the change in incidence of intestinal metaplasia (IM) in healthy, young adults over 10 years. MATERIALS AND METHODS: Urease test and histopathology by endoscopic biopsies were performed from volunteers between 1995 and 2005. Histopathological grade was assessed using the updated Sydney System. RESULTS: In total, 714 subjects with a median age of 22.4 years were enrolled. Helicobacter pylori was observed at the antrum and body in 44.5% and 35.1%, respectively. IM limited to the antrum was present in 1.1% of the subjects. The degree of IM correlated negatively with age (P=0.04) but there was no correlation with H. pylori levels or the degree of chronic or active gastritis. Compared to the beginning of the study period, the positivity rate at the end of the study period droped to 45%. IM incidence did not change over the 11-year study period, whereas H. pylori-positivity and the frequency of chronic and active gastritis in the antrum and body dropped significantly over this period (P<0.05). CONCLUSIONS: This result suggests that other factors, besides chronic H. pylori infection or degree of gastritis, may contribute to the progression of atrophy to IM in healthy, young adults.

The first pediatric case of tularemia in Korea: manifested with pneumonia and possible infective endocarditis / 소아과

Tularemia is a potentially severe zoonotic disease caused by Francisella tularensis. A lack of awareness about tularemia can be embarrassing and could result in delayed treatment because of improper diagnosis. The diagnosis of tularemia is difficult, because the infections are rare and the clinical spectrum is broad. As only 1 adult case has been reported in Korea thus far, pediatricians in Korea may be unfamiliar with tularemia. We report our experience with a 14-year-old male adolescent with tularemia who presented with atypical pneumonia and possible infective endocarditis. Although the infectivity and mortality rates for tularemia are very high if left untreated, we did not suspect tularemia in this case until the incidental isolation of F. tularensis. The present case suggests that clinicians in Korea should be more aware of tularemia. This case also suggests that tularemia should be considered in undetermined cases of atypical pneumonia or acute febrile illness without local signs.

Differences in Clinical and Laboratory Findings between Group D and Non-Group D Non-Typhoidal Salmonella Gastroenteritis in Children / 대한소아소화기영양학회지

PURPOSE: To investigate the differences in clinical features and laboratory findings between group D and non-group D non-typhoidal Salmonella (NTS) gastroenteritis in children. METHODS: A retrospective chart review of children diagnosed with NTS confirmed by culture study was performed. The clinical features and laboratory findings of group D and non-group D NTS were compared. RESULTS: From 2003 to 2012, 75 cases were diagnosed as NTS at our center. The number of group D and non-group D patients was 45 and 30, respectively. The mean age was higher in group D than in non-group D patients (5.1 years vs. 3.4 years, p=0.038). Headaches were more frequently observed (p=0.046) and hematochezia was less frequently observed (p=0.017) in group D than in non-group D NTS gastroenteritis patients. A positive Widal test result was observed in 53.3% of group D and 6.7% of non-group D NTS cases (O-titer, p=0.030; H-titer, p=0.039). There were no differences in white blood cell counts, level of C-reactive protein and rate of antimicrobial resistance between group D and non-group D cases. CONCLUSION: The more severe clinical features such as headache, fever, and higher Widal titers were found to be indicative of group D NTS gastroenteritis. Additionally, group D NTS gastroenteritis was more commonly found in older patients. Therefore, old age, fever, headache, and a positive Widal test are more indicative of group D NTS than non-group D NTS gastroenteritis. Pathophysiological mechanisms may differ across serologic groups.

Differences in Clinical and Laboratory Findings between Group D and Non-Group D Non-Typhoidal Salmonella Gastroenteritis in Children / 대한소아소화기영양학회지

PURPOSE: To investigate the differences in clinical features and laboratory findings between group D and non-group D non-typhoidal Salmonella (NTS) gastroenteritis in children. METHODS: A retrospective chart review of children diagnosed with NTS confirmed by culture study was performed. The clinical features and laboratory findings of group D and non-group D NTS were compared. RESULTS: From 2003 to 2012, 75 cases were diagnosed as NTS at our center. The number of group D and non-group D patients was 45 and 30, respectively. The mean age was higher in group D than in non-group D patients (5.1 years vs. 3.4 years, p=0.038). Headaches were more frequently observed (p=0.046) and hematochezia was less frequently observed (p=0.017) in group D than in non-group D NTS gastroenteritis patients. A positive Widal test result was observed in 53.3% of group D and 6.7% of non-group D NTS cases (O-titer, p=0.030; H-titer, p=0.039). There were no differences in white blood cell counts, level of C-reactive protein and rate of antimicrobial resistance between group D and non-group D cases. CONCLUSION: The more severe clinical features such as headache, fever, and higher Widal titers were found to be indicative of group D NTS gastroenteritis. Additionally, group D NTS gastroenteritis was more commonly found in older patients. Therefore, old age, fever, headache, and a positive Widal test are more indicative of group D NTS than non-group D NTS gastroenteritis. Pathophysiological mechanisms may differ across serologic groups.