Declining trend in the seroprevalence of infection with hepatitis A virus in Thailand.

Since the mid 1970s, infection with hepatitis A virus (HAV) in Thailand has shifted from hyper-endemic to mesoendemic. In 2004, to explore this trend in prevalence further, 3997 subjects from four geographically distinct provinces of Thailand were tested, in a commercial ELISA, for antibodies to HAV. The results indicate that the seroprevalence of HAV continues to fall, almost certainly because the profound socio-economic development that has occurred over the last few decades in Thailand has brought with it significant improvements in sanitation and personal hygiene. As exposure to HAV declines, however, the risks of symptomatic and potentially severe infection in adulthood (rather than asymptomatic infection during childhood) and of epidemics of such infection, which would lead to profound economic loss, increases. Improvements in hygiene and sanitation to reduce exposure to the virus and measures to reduce the incidence of symptomatic disease in those infected, such as vaccination (which may only be cost-effective when targeted at high-risk groups), need to be carefully considered.

Perinatal HIV infections in Thailand.

A collaborative study group of researchers from seven hospitals from all regions of Thailand was formed to collect information on children born to HIV-infected mothers since the beginning of the first hospital case until the end of June 1994. The study conducted to verify the status of perinatal transmission of HIV infection in Thailand showed a rapid increase in HIV seropositivity among Thai mothers with vertical transmission rates varying between 25% in Rayong and 42% in Chiang Rai Hospitals, respectively. The majority of children with symptomatic HIV infection had clinical presentations of delayed growth development, pneumonia, diarrhea, oral candidiasis, lymphadenopathy, hepato-splenomegaly. Cases of Penicillium marneffei infection were found only at Chiang Rai Prachanukroh Hospital. The ages at which diagnosis of HIV disease was made were mostly within the first year of life. One third of children with AIDS died during the period of study.

Immunogenicity of low dose Japanese encephalitis vaccine (BIKEN) administered by the intradermal route: preliminary data.

Two hundred twenty-four immune and non-immune adults were systematically assigned to receive a single dose of Nakayama strain JEVAC in one of four study "arms": 0.1 ml ID, 0.2 ml ID (injection of 0.1 ml at two sites), 0.3 ml ID (injection of 0.1 ml at three sites), or 1.0 ml SC. Immune responses after this single dose (in many cases "booster") was assumed to reflect immune responses of a primary series and was assessed qualitatively (percent seroconvertion) and quantitatively (geometric mean titer) a 30 and 90 days post immunization. The results showed that JEVAC given 0.1 ml. ID at two sites is likely to be as immunogenic as 1.0 ml. given SC.