One-dose intradermal rabies booster enhances rabies antibody production and avidity maturation.

The incidence of rabies in Thailand reached its peak in 2018 with 18 human deaths. Preexposure prophylaxis (PrEP) vaccination is thus recommended for high-risk populations. WHO has recently recommended that patients who are exposed to a suspected rabid animal and have already been immunized against rabies should receive a 1-site intradermal (ID) injection of 0.1 mL on days 0 and 3 as postexposure prophylaxis (PEP). In Thailand, village health and livestock volunteers tasked with annual dog vaccination typically receive only a single lifetime PrEP dose and subsequent boosters solely upon confirmed animal bites. However, the adequacy of a single PrEP dose for priming and maintaining immunity in this high-risk group has not been evaluated. Therefore, our study was designed to address two key questions: (1) sufficiency of single-dose PrEP-to determine whether a single ID PrEP dose provides adequate long-term immune protection for high-risk individuals exposed to numerous dogs during their vaccination duties. (2) Booster efficacy for immune maturation-to investigate whether one or two additional ID booster doses effectively stimulate a mature and sustained antibody response in this population. The level and persistence of the rabies antibody were determined by comparing the immunogenicity and booster efficacy among the vaccination groups. Our study demonstrated that rabies antibodies persisted for more than 180 days after cost-effective ID PrEP or the 1st or the 2nd single ID booster dose, and adequate antibody levels were detected in more than 95% of participants by CEE-cELISA and 100% by indirect ELISA. Moreover, the avidity maturation of rabies-specific antibodies occurred after the 1st single ID booster dose. This smaller ID booster regimen was sufficient for producing a sufficient immune response and enhancing the maturation of anti-rabies antibodies. This safe and effective PrEP regimen and a single visit involving a one-dose ID booster are recommended, and at least one one-dose ID booster regimen could be equitably implemented in at-risk people in Thailand and other developing countries. However, an adequate antibody level should be monitored before the booster is administered.

HIV RNA measurement in dried blood spots of HIV-infected patients in Thailand using Abbott m2000 system.

World Health Organization recommends using dried blood spots (DBS) for HIV RNA viral load (VL) measurement whenever plasma processing is not convenient or feasible. DBS collected from 80 treatment-naïve HIV-infected patients presenting in three hospitals of two different regions of Thailand were shipped to a central laboratory along with corresponding plasma specimens. Viral load was measured in both DBS and plasma using the Abbott m2000 system. HIV RNA levels were strongly correlated (r = 0.94) with a mean of differences of 0.23 log10 copies/mL. Using the 1,000 copies/mL cut-off, the sensitivity of DBS was 97% (95%CI, 91-100%) and specificity was 75% (95%CI, 19-99%). DBS are useful to scale-up HIV RNA VL testing in settings with limited access to VL testing.

Prevalence of chronic hepatitis B virus infection in Thailand: a systematic review and meta-analysis.

OBJECTIVE: To estimate the number of people living in Thailand with chronic hepatitis B (CHB), a major cause of liver cirrhosis and cancer, in view of the implementation of programs to prevent CHB complications. METHODS: Using PubMed/Medline and ScienceDirect, all studies reporting hepatitis B surface antigen (HBsAg) seroprevalence estimates conducted in Thailand and published between 1975 and 2015 were reviewed systematically. Pooled prevalence estimates and their 95% confidence intervals (CIs) were calculated, and potential sources of heterogeneity investigated. RESULTS: A high heterogeneity was observed between prevalence estimates. There was a significant decrease in the 150 estimates of HBsAg prevalence with more recent decades of birth (p<0.001), even before the implementation of the national universal immunization program in 1992. When restricted to the general population, the pooled prevalence estimate was 5.1% (95% CI 4.3-6.0%), which would translate to an estimated number of individuals with CHB living in Thailand in 2015 as high as three million. CONCLUSIONS: The high burden of CHB in Asian countries is a major challenge for the incorporation of national programs to prevent CHB complications within health care systems.

Prevention of mother-to-child transmission of hepatitis B virus: a phase III, placebo-controlled, double-blind, randomized clinical trial to assess the efficacy and safety of a short course of tenofovir disoproxil fumarate in women with hepatitis B virus e-antigen.

BACKGROUND: Chronic hepatitis B virus (HBV) infection is complicated by cirrhosis and liver cancer. In Thailand, 6-7 % of adults are chronically infected with HBV. The risk of mother-to-child transmission (MTCT) of HBV has been estimated to be about 12 % when mothers have a high hepatitis B viral load, even if infants receive passive-active prophylaxis with HBV immunoglobulin (HBIg) and initiate the hepatitis B vaccine series at birth. We designed a study to assess the efficacy and safety of a short course of maternal tenofovir disoproxil fumarate (TDF) among women with a marker of high viral load for the prevention of MTCT of HBV. METHODS: The study is a phase III, multicenter (17 sites in Thailand), placebo-controlled, double-blind, randomized 1:1, two-arm clinical trial of TDF 300 mg once daily versus placebo among pregnant women from 28 weeks' gestation through 2-month post-partum. All infants receive HBIg at birth, and a hepatitis B (HB) vaccination series according to Thai guidelines: birth, and age 1, 2, 4 and 6 months. Participant women at study entry must be age ≥18 years, hepatitis B surface antigen (HBsAg) and e-antigen (HBeAg) positive, have alanine aminotransferase (ALT) level < 30 IU/L at screening (confirmed < 60 IU/L pre-entry), negative hepatitis C serology, creatinine clearance >50 mL/min, and no history of anti-HBV antiviral treatment. The target sample size of 328 mother/infant pairs assumed 156 evaluable cases per arm to detect a ≥9 % difference in MTCT transmission (3 % experimental arm versus 12 % placebo arm) with 90 % power. Mothers and infants are followed until 12 months after delivery. The primary infant endpoint is detection of HBsAg, confirmed by detection of HBV DNA at six months of age. Secondary endpoints are maternal and infant adverse events, acute exacerbations of maternal hepatitis B disease (ALT >300 IU/L, defined as a "flare") following discontinuation of study treatment, infant HBV infection status and growth up to 12 months of age. DISCUSSION: The results of this randomized trial will clarify the efficacy and safety of a short course of antiviral treatment to prevent mother-to-child transmission of HBV and inform international guidelines. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT01745822 .