ABSTRACT
The prevalence of antibodies to hepatitis A virus was studied in 961 children and adolescents, randomly selected from five different provinces in Thailand (Chonburi, Lopburi, Udonthani, Nakhon Si Thammarat and Lopburi). The highest prevalence was found in Nakhon Si Thammarat, with 32.1 percent of those aged 10-14 years and 57.1 percent of those aged 15-18 years showing evidence of protective immunity. However, this high rate could be explained by an outbreak of hepatitis A in 1992. In the remaining four provinces, the pattern was typically age-related in that all individuals showed between zero and 13 percent antibody prevalence until reaching the 15-to-18-year age group where it increased to between 5.6 and 22.7 percent. The overall sero-prevalence among all age groups was 7.9 percent. Thus, the majority of the younger generation is susceptible to hepatitis A virus infection thereby enhancing the impact, should an outbreak occur. Preventive measures that might be taken are education aimed at better hygiene and sanitation, as well as vaccination of susceptible individuals within high-risk populations.
Subject(s)
Adolescent , Child , Child, Preschool , Disease Susceptibility/immunology , Hepatitis A/epidemiology , Hepatitis A Antibodies , Hepatitis Antibodies/blood , Humans , Infant , Seroepidemiologic Studies , Thailand/epidemiologyABSTRACT
One hundred and twenty-three children who had received no, incomplete and complete primary hepatitis B vaccination but had negative or very low anti-HBs titer were immunized with a single dose of recombinant hepatitis B vaccine. Blood tests for anti-HBs were obtained at 30 +/- 5 days after the booster immunization. Twelve of 18 (66.7%) children without prior immunization (group 1) seroconverted following the single dose Seroconversion rates in children who had undetectable anti-HBs with incomplete and complete primary immunization (group 2 and 3) were 83.34% and 94.5%, respectively. All children with complete 3- dose vaccination but who had low anti-HBs titer (group 4) also seroconverted. This study confirmed that immunological memory, allowing a protective anamnestic response, lasted at least 8 years in children who had received primary HB immunization with undetectable anti-HBs. Therefore, we conclude that the booster dose after complete vaccination is not necessary in healthy children.
Subject(s)
Child, Preschool , Hepatitis B Antibodies/biosynthesis , Hepatitis B Vaccines/administration & dosage , Humans , Immunization, Secondary , Thailand , Treatment Outcome , Vaccines, Synthetic/administration & dosageABSTRACT
Hepatitis A antibody prevalence in Southeast Asia has markedly declined among children and adolescents. Therefore increasing a number of susceptible populations could result in an outbreak or epidemic. This paper reports an intensive study of an outbreak of hepatitis A in a primary school children during an endemic at Nakhon Si Thammarat, Southern Thailand. Eighty-nine children were inspected randomly from the total of 269 students, age ranged from 7-12 years old. The school children and parents were interviewed for their illness. Serological tests for antiHAV IgM and antiHAV (total antibody) were performed by ELISA. There were 36 cases of clinical acute hepatitis were positive for antiHAV IgM because of serological tests were performed nearly 4 months later. Seventy of 89 children tested were positive for antiHAV and 16 of them were positive for IgM class. Seven of 16 children with antiHAV IgM positive were asymptomatic. The significant risk factors for children with positive antiHAV were occurrence of hepatitis patients in the family and no latrine (p < 0.01). Endemic transmission in this outbreak occurred rapidly. Therefore preventive measures are essential in reducing the infection rate. In addition to personal hygiene, immunoprophylaxis with either immunoglobulin or HAV vaccine is recommended.