Increasing susceptibility to HAV among members of the young generation in Thailand.

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.

Cost benefit analysis of Japanese encephalitis vaccination program in Thailand.

Using decision analysis, we estimated benefits, risks, and costs of implementing the Japanese encephalitis (JE) vaccination program in children aged 18 months and 6 years in Thailand. The costs for inclusion of JE vaccine into the routine immunization program at 18 months and 6 years are $2.16 and $3.68 per person, respectively. In the baseline model, the JE vaccination program will prevent 124 JE cases in the program for 18 months old children and 153 JE cases in the program for 6 years old children. The 18 month child program is more cost-effective than the 6 year child program. The cost-effectiveness ratio in the 18 month child program is $15,715 compared with $21,661 in the 6 year child program. The benefits of the JE vaccination program are the savings in treatment cost, disability care, and the future lifetime earnings from JE prevented. The 18 month child program will save $72,922 per one prevented JE compared with $66,197 in the 6 year child program. The JE vaccination program is cost-beneficial under the base-case assumption. Sensitivity analysis which alters various assumptions indicates that the JE vaccination program is worth implementing unless the incidence of JE is less than 3 per 100,000 population. Otherwise, the cost of vaccine has to be reduced.

Frequency and risk of HIV infection among men attending a clinic for STD in Chiang Mai, Thailand.

A prospective study was conducted in the Chiang Mai Sexually Transmitted Diseases Clinic to determine the frequency of HIV seroconversion among men following high risk sexual contacts and to establish risk factors for HIV infection. HIV antibodies were detected in 26 out of 150 men on the initial recruitment with a seroprevalence rate of 21%. Among 124 initial HIV negative subjects; 100, 77, 68, and 55 subjects were followed for 2, 4, 12, and 24 weeks, respectively. One subject had HIV seroconversion documented with the rate of 1.0% (1/100, 95% confidence interval [CI] = 0.03-5.4%). Logistic regression analysis found significantly independent associations of HIV prevalence with prostitute visits at least once a month (OR = 3.6, 95% CI = 1.2-10.9), and with cigarette smoking (OR = 3.5, 95% CI = 1.2-10.5). Intensive health education should be elucidated to decrease the high rate of HIV infection among this population.