A review of Hib epidemiology in Asia.

Meningitis due to an invasive Haemophilus influenzae type b (Hib) infection, has been previously perceived to be relatively uncommon in Asia. However, the incidence of disease and its impact may have been underestimated. In addition to a lack of microbiological facilities in some hospitals, difficulties in culturing the organism and the widespread use of antibiotics may have hidden the true incidence of the disease in some countries. Furthermore, the reported disease burden probably underestimates the incidence of Hib pneumonia. The epidemiology of invasive Hib disease for various Asian nations is reviewed in this paper. Hospital-based studies show that Hib is a major cause of bacterial meningitis and/or pneumonia in the Philippines, India, Thailand, Malaysia, Indonesia and Vietnam. Singapore and Hong Kong have a low incidence of infection compared with Western and other Asian nations. This low incidence is not due to a higher level of natural protective antibodies, but may be related to an interaction between environmental and genetic factors. Therefore the widespread belief that Hib infection is unimportant in Asia does not refer to Asia as a whole and possibly to Chinese patients only, and failure to recognize this has serious implications. The inclusion of Hib vaccine in the routine infant immunization schedule in many industrialized nations has significantly reduced the incidence of invasive disease. Recent studies have shown Hib vaccination is also effective in preventing invasive disease in children in developing countries. While population-based data may be required to confirm the need for public-funded infant Hib immunization in Asia, its introduction in countries with a high incidence of Hib meningitis and/or pneumonia has the potential to significantly improve pediatric health and survival.

Experience with the active immunization method for determining the potency of typhoid vaccine

The study was done to gain experience with the active immunization method for vaccine potency testing. It also determined the relative potency of locally prepared vaccines compared with foreign prepared vaccinesWhite Swiss mice equally distributed as to sex were used as control and test groups. Granular mucin type 1201-w, strain of Salmonella typhosa, and three vaccines (vaccines A,B, and C) were used. The procedure used was the mucin technique of RakeThe LD50 dose was found to be 0.5 ml of a dilution of 10-5-752. It was felt necessary to enhance virulence of the organism, thus another determination was done after two passages. Results of potency determination showed that vaccine A gave a protection to approximately 1,500 LD50 dose. However, vaccines B and C failed to protect immunized animals against the minimal number of LD50 doses measurable in the range of the tests conductedFurther studies involving V: antigen are deemed needed to supplement this initial experience

Hepatitis A virus: declining seroprevalence in children and adolescents in Southeast Asia.

The prevalence of hepatitis A virus (HAV) in a country largely reflects its standards of hygiene and socioeconomic conditions. Countries which undergo socioeconomic development show major change in HAV prevalence from high to low endemicity, and this is largely reflected in patterns of age-related seroprevalence. This paper presents age-related HAV seroprevalence patterns of SE Asian countries, and highlights how these patterns have changed over recent decades. Singapore, Thailand and Malaysia have experienced a decline in childhood and adolescent HAV seroprevalence, typical of countries which undergo socioeconomic development. By contrast, India has remained a country of high endemicity, with almost universal seroconversion in childhood. The Philippines and Vietnam show age-related seroprevalence patterns typical of high to moderate endemicity, while Indonesia shows significant regional variation in HAV seroprevalence. Populations within countries which exhibit major improvements in endemicity and age related HAV seroprevalence patterns are at risk of HAV epidemics, and a paradoxical increase in incidence tends to occur as seroconversion shifts from children to adults. The residents of these countries, a significant number of whom are at-risk, would benefit from a program of vaccination, as would non-infected individuals visiting high-risk areas.