Protective antibody after a 'one dollar' hepatitis B vaccine.

The seropositivity rate of anti-HBs after hepatitis B vaccines, "Hepavax B", a one-dollar per dose vaccine produced by Korean Green Cross Corporation, Korea which were widely distributed and used for the first few years in the National Expanded Program on Immunization in Thailand were assessed in children who regularly came for immunization at the Well Baby Clinic at the Children's Hospital between June to December 1994. The schedule for hepatitis B immunization is at birth, 2 and 6 months of age. The seropositivity rate of anti-HBs at 6 months after the last dose were 86.3% and 87.7% at 12 months which was comparable to the seropositivity rate after other more expensive hepatitis B vaccines at 2 years (88.1%). This result should convince people that a one-dollar hepatitis B vaccine, "Hepavax" is immunogenic and expected to be as effective as other expensive hepatitis B vaccines. The marked reduce in the cost of hepatitis B vaccines will enable us to prevent and ultimately control of worldwide hepatitis B infections in the future.

A field study on Nakayama and Beijing strains of Japanese encephalitis vaccines.

A field study to compare the immune response of children aged 1-6 years to Nakayama and Beijing strains JE vaccines was carried out in Mae Hong Son Province, northwest Thailand, where there was low incidence of JEV infection. The first and second dose of each vaccine was given 1-2 weeks apart and the third dose was 1 year after the second dose. Seroconversion rate was similarly high, about 94% in both groups of vaccinees. At 6 and 12 months after 2 doses of vaccines, the seroconversion rates dropped in both groups of vaccinees, so there were 10-20% of children (50-65% if cross protection was considered) susceptible to JEV infections during this period. After the third dose of vaccine, the seroconversion rate rose to 100% in both groups. The GMT in Bejing strain vaccinees were slightly higher than Nakayama strain JE vaccines. To reduce the number of susceptible children during 6-12 months after the second dose and for longer protection, the primary JE immunization should be 3 doses and the timing for the third dose should be at 6 months after the second dose. Either Nakayama or Beijing strain vaccine could be used in Thailand.

Age-specific prevalence of hepatitis A antibody in Thai children.

Age-specific prevalence of anti-HAV was determined for 3 groups of children whose mean ages were 12.6, 20.7 and 52.5 months. There were 41, 43 and 99 children in the respective age groups. All children were healthy, from middle to low socioeconomic families in Bangkok and vicinity. None of the children in the two younger age groups had anti-HAV antibody while 2 of 99 children in the oldest age group did. One of them resided in central Bangkok (Amphoe Dusit) and the other in Nonthaburi Province. The overall prevalence of anti-HAV in children under 5 years old was 1.1%. This demonstrates that hepatitis A transmission rates in Bangkok are very low when compared to ten years ago when prevalence rates were as high as 50-65%. From this study hepatitis A vaccine is recommended for 4-5 years old children in Bangkok. We need more epidemiologic data concerning hepatitis A transmission in Thailand before we can consider hepatitis A immunization for the whole country.

A study of erythrocyte sedimentation rate in dengue hemorrhagic fever.

Erythrocyte sedimentation rate (ESR) was determined in 180 DHF patients and 70 patients with various viral and bacterial infections using the Winthrobe method. Seventy-seven percent of DHF patients had normal ESR (less than 20 mm/hour) and 15% had slightly elevated ESR value (between 21-30 mm/hour). The other 8% had ESR in the range of 31-49 mm/hour. Among 7 patients in the latter group, one had definite evidence of complicating urinary tract infection while the other 6 cases had anemia and severe bleeding. The mean ESR in DHF patients (10.71 mm/hour) was significantly lower than the mean values in other groups of patients with viral infection (20.46 mm/hour), bacterial infection (34.81 mm/hour) and miscellaneous illnesses (35.29 mm/hour). The mean ESR in shock cases was 7.63 mm/hour while in non-shock cases it was 13.87 mm/hour and they are statistically different (p less than 0.05). The mean ESR during the time of shock was lower than in the pre-shock and post-shock period. Hemoconcentration, low level of albumin and fibrinogen and the presence of disseminated intravascular clotting (DIC) in a majority of DHF patients are most likely responsible to this observed lower ESR especially during shock period. The determination of ESR, which is simple, is therefore useful in differentiating DHF from bacterial infections and dengue shock syndrome from septic shock.