OBJECTIVES: During March-May, 2000, a measles outbreak occurred at Youngduk, Korea. This county is divided into two areas with different historical and socioeconomic background. The outbreak occurred in one of these areas. We conducted a comparative epidemiologic study on the two areas in order to evaluate the factors related to the epidemic. MATERIALS AND METHODS: We selected two groups, grades 3 and 5 in a primary schools in each area. We investigated outbreak-related factors using parent-questionnaires, the vaccination history from the students health record and the records concerning the recent measles-outbreak from the local health center. Serologic test on measles-IgG and -IgM antibody was done. RESULTS: The infection rate was 31.6% for the epidemic area and 3.7% for non-the epidemic area according to clinical or serological criteria (p<0.001). No difference was seen in the measles vaccination rate, residence at the time of vaccination or past measles infection history between the two areas. In the epidemic area, the attack rate for the 4-6 year-old MMR booster group(20.5%) was higher than the non-booster group(32.4%), but was not found significantly. Vaccine efficacy was 29.6% in the epidemic area and 87.0% in the non-epidemic area (p<0.001). The IgG level and positive rate were significantly different between the two areas (median 10727 IU/ml, 98.9% in epidemic area; median 346 IU/ml, 85.9% in the non-epidemic area, p<0.001). However, the IgG level and positive rate between the measles-cases and non-cases were not significantly different. CONCLUSIONS: This outbreak took place in mostly vaccinated children. These results suggest that a reduction of herd immunity for immunity failure after vaccination may be one of the feasible factors related to the outbreak pattern in the two areas. The results of the IgG level and positive rate suggest that re-establishment of a normal value for IgG level and of a qualitative method for IgG are needed.
Child ; Epidemiologic Studies ; Humans ; Immunity, Herd ; Immunoglobulin G ; Korea ; Measles* ; Reference Values ; Serologic Tests ; Vaccination

The epidemiology of human group A rotavirus was analyzed by examining genotypic data acquired from 1989 to 2009 in South Korea. This information was derived from all the available published articles on rotavirus studies in South Korea, retrieved from both the PubMed and KoreaMed databases. Four common G types (G1, G2, G3, and G4) and three common P types (P[8], P[4], and P[6]) accounted for approximately 93% and 99% of the rotavirus reports, respectively. The G9 type was frequently detected after 2000, and because of this prevalence, it is considered to be the fifth most important G type rotavirus after the G1.G4 genotypes. Less common G types of the virus such as G12, G11, and G10 were detected in some geographic settings, and it is important to consider the context of these subtypes and their epidemiological significance. The P[9] virus genotype was observed in the study and has been discussed in many other studies; however, the P[3], P[10] and P[25] genotypes were rarely detected in the epidemiological research. In general, the distributions of the G and P genotypes showed temporal and geographical fluctuations, and a nationwide rotavirus vaccine program that targeted these genotypes demonstrated effectiveness in protecting against the circulating rotavirus strains. However, further analysis is needed to determine the true long-term effectiveness of these vaccines; the analysis should also consider the unexpected effects of vaccinations, such as vaccine-induced diseases, herd immunity, and changes in host susceptibilities.
Epidemiology ; Genotype* ; Humans ; Immunity, Herd ; Prevalence* ; Republic of Korea* ; Rotavirus* ; Vaccination ; Vaccines ; Viruses

Humans ; Mass Vaccination ; COVID-19 Vaccines/therapeutic use* ; COVID-19/prevention & control* ; Immunity, Herd ; Vaccination

PURPOSE: To evaluate the epidemiologic characteristics of aseptic meningitis in Daejeon, Korea from 1987 to 2003. METHODS: A total of 2201 medical records of children with aseptic meningitis admitted to the Catholic University of Korea, Daejeon St. Mary's Hospital, was retrospectively analyzed. RESULTS: The mean annual number of cases was 129, with a higher rate of occurrence in the summer season(May to August, 74.1%). Outbreaks of aseptic meningitis were noted in the years 1990, 1993, 1996, 1997, 2001, and 2002. The age distribution was relatively even, with higher incidences in the 4-7 years group and in the under one year old group. The male-to-female ratio was 2 : 1. Comparing the epidemics of 1997 and 2002, there were no marked differences in age distribution, except in the less than 1 year old age group(11.8% vs. 4.4%), nor in the monthly incidence. Neurologic complications were found in 0.7% of the patients. CONCLUSION: Outbreaks of aseptic meningitis occurred every one to three years in Daejeon, reflecting typical nationwide epidemics that occurred from 1987 to 2003. The incidence of disease in the less than 1 year age group during each epidemic may reflect the herd immunity of the maternal generation.
Age Distribution ; Child ; Disease Outbreaks ; Epidemiologic Studies* ; Epidemiology ; Humans ; Immunity, Herd ; Incidence ; Korea ; Medical Records ; Meningitis, Aseptic* ; Retrospective Studies

Kawasaki disease that had been identified and reported as a new syndrome complex by a Japanese pediatrician Kawasaki in 1967 still remains as a disease of unknown etiology despite the enormous research efforts throughout the world. We conducted this literature review study with an attempt to formulate causal gypothesis on Kawasaki disease based on research findings published. Summarizing the research results in terms of clinical, pathologic and epidemiologic characteristics we could characterize the causative agent as followings: (1) The agent should have high infectivity and low pathogenicity causing generalized infection, perhaps with more frequent inapparent infection than apparent infection, particularly among immunocompromized, feeble children by preceded infection, (2) The target organ of the agent seems to be endothelial cells of arteries, (3) The agent appears to take airborne transmission route in very special environment where the agent can be supplied by reservoirs other than human beings, and (4) the agent should be quite ubiquitous around human living environment resulting in high herd immunity among adult population. For the time being we propose Coxiella burneti as a possible causative agent that could satisfy the most of the above characteristics.
Adult ; Arteries ; Asian Continental Ancestry Group ; Child ; Coxiella ; Endothelial Cells ; Humans ; Immunity, Herd ; Mucocutaneous Lymph Node Syndrome* ; Virulence

The importance of vaccine on public health is related to the herd protection related to the levels of vaccine coverage, which directly influences the vaccinated individuals as well as the unvaccinated community. Reaching the level of herd protection by increasing vaccine coverage is the basic strategy to eradicate related infectious diseases. Again, herd protection has played an important role in public health practices. With the increasing interests in estimating the vaccine herd protection, we however, have seen only few relevant papers including observational population-based and cluster-randomized clinical trials reported in China. We hope to discuss the study designs for evaluating the vaccine herd protection in order to generate evidence-based related research in this field.
China/epidemiology* ; Communicable Disease Control ; Communicable Diseases/immunology* ; Humans ; Immunity, Herd/immunology* ; Research Design ; Vaccination/trends* ; Vaccines/immunology*

Outbreaks of porcine reproductive and respiratory syndrome virus (PRRSV) in vaccinated sow herds from occurrence to stabilization were monitored and analyzed in terms of serology and reproductive performance. Three different conventional pig farms experienced severe reproductive failures with the introduction of a type 1 PRRSV. These farms had adopted mass vaccination of sows using a type 2 PRRSV modified live vaccine (MLV). Therefore, to control the type 1 PRRSV, an alternative vaccination program utilizing both type 1 and type 2 MLV was undertaken. Following whole herd vaccinations with both types of MLV, successful stabilization of PRRS outbreaks was identified based on serological data (no viremia and downward trends in ELISA antibody titers in both sows and suckling piglets) and recovery of reproductive performance. Additionally, through comparison of the reproductive parameters between outbreak and non-outbreak periods, it was identified that PRRSV significantly affected the farrowing rate and the number of suckling piglets per litter at all three pig farms. Comparison of reproductive parameters between periods when the different vaccination strategies were applied revealed that the number of piglets born in total and born dead per litter were significantly increased after the introduction of the type 1 PRRS MLV.
Agriculture ; Disease Outbreaks ; Enzyme-Linked Immunosorbent Assay ; Immunity, Herd ; Immunity, Heterologous ; Mass Vaccination ; Porcine Reproductive and Respiratory Syndrome ; Porcine respiratory and reproductive syndrome virus ; Vaccination ; Viremia

Pertussis is a pediatric infectious disease with one of the highest degrees of infectivity. Although pertussis may cause asymptomatic infections in children and adults with immunity, it can cause life-threatening diseases in newborn babies or infants. We report three cases of pertussis in infants <3 months of age without DTaP immunization who have received symptomatic treatment with the diagnosis of bronchiolitis from other hospitals, and subsequently correctly diagnosed and treated. The patients did not have the characteristic whooping cough, but the main symptoms were episodic cough, intermittent vomiting, and cyanosis. Based on culture results for Bordetella pertussis and PCR, pertussis was diagnosed and treated without any complications. As it is assumed that adults, adolescents, and asymptomatic patients may serve as sources of infection, immunization with Tdap vaccine is recommended to prevent dissemination of pertussis from adolescents and adults to infants, and thus maintain herd immunity.
Adolescent ; Adult ; Asymptomatic Infections ; Bordetella pertussis ; Bronchiolitis ; Child ; Communicable Diseases ; Cough ; Cyanosis ; Humans ; Immunity, Herd ; Immunization ; Infant ; Infant, Newborn ; Polymerase Chain Reaction ; Vomiting ; Whooping Cough

Haemophilus influenzae type b(Hib) conjugate vaccines prevent Hib disease in individuals and reduce the carriage and transmission of the organism in the community. The incidence of Hib disease has been decreased dramatically in a diverse range of countries through the use of a variety of conjugate vaccines and vaccine schedules. In some countries, the vaccine has caused a near-disappearance of invasive Hib disease through a combination of direct protection and herd immunity. The effectiveness of the vaccine was not modified by the type of conjugate vaccine, the number of doses given(two, three or four), age at first vaccination(two months, 42 to 90 days, three months) and whether the vaccine was tested in an industrialized or developing country. Over 15 years of international experience with vaccines has also demonstrated that they are safe. In 2004, Hib vaccines were adapted in routine immunization in 92 countries in the world. Decisions regarding the use of the Hib vaccine in routine immunization schedules depend not only on the effectiveness and efficacy of the vaccine but also on factors such as burden of disease, vaccine cost, and competing priorities. In Korea, Hib disease burden seemed to be lower than other developed countries(~10/100,000). Moreover Hib vaccines showed excellent immunogenicity in Korean children in many studies. Therefore, a potential approach to economize the cost of Hib vaccines could be to explore the possibilities of using reduced vaccine doses for immunization as some other countries.
Appointments and Schedules ; Child ; Developing Countries ; Haemophilus influenzae type b ; Haemophilus influenzae* ; Haemophilus* ; Humans ; Immunity, Herd ; Immunization Schedule ; Immunization* ; Incidence ; Korea ; Vaccines ; Vaccines, Conjugate

BACKGROUND: Diphtheria epidemics in Russia have spread to all the other independent states of the former Soviet Union and East European countries around 1990s. One of the most important measures in preventing diphtheria is to maintain high levels of immunity in the population. We studied the diphtheria antibody levels of 1,086 participants to investigate herd immunity in Korea. METHODS: The tested 1,086 serum specimens were collected from healthy individuals from September 1995 to March 1996. Diphtheria antitoxin titers were measured by a micro cell culture method using Vero cells. Antibody titer of 0.01 IU/ml to neutralize diphtheria toxin is an internationally accepted protective level. RESULTS: We studied the diphtheria antitoxin titer levels of 1,086 cases consisting of 579 males and 507 females. The proportion of protective antitoxin level to diphtheria is 69.2%. Diphtheria antitoxin levels showed no significant difference between males and females. The highest seropositive rate was observed in the 5 to 9-year old age group(95.8%). The seropositivity rate declined with age. The lowest seropositive rate was observed in the 20~39 years of age, maximally 43.4 %. Over 40 years of age, the seropositive rates increased again. CONCLUSION: The antibody titers in the Korean population declined from 95.8% to below 50% with age in the 1~39 year-old age group. To maintain the rate of population with protective antibodies to diphtheria, we recommend Td booster immunization to adults with low antitoxin titers and continuous survey for antitoxin titers.
Adult ; Antibodies ; Cell Culture Techniques ; Child ; Diphtheria Antitoxin ; Diphtheria Toxin ; Diphtheria* ; Female ; Humans ; Immunity, Herd ; Immunization, Secondary ; Korea ; Male ; Russia ; USSR ; Vero Cells