Adult immunization is a neglected and underpublicised issue in Southeast Asia. Vaccine-preventable diseases cause unnecessary morbidity and mortality among adults in the region, while inadequate immunization results in unnecessary costs, including those associated with hospitalization, treatment, and loss of income. Childhood vaccination coverage is high for the EPI diseases of diphtheria, tetanus and pertussis; however, unvaccinated, undervaccinated, and aging adults with waning immunity remain at risk from infection and may benefit from vaccination. Catch-up immunization is advisable for adults seronegative for hepatitis B virus, while immunization against the hepatitis A and varicella viruses may benefit those who remain susceptible. Among older adults, immunization against influenza and pneumococcal infections is likely to be beneficial in reducing morbidity and mortality. Certain vaccinations are also recommended for specific groups, such as rubella for women of child-bearing age, typhoid for those travelling to high-endemicity areas, and several vaccines for high-risk occupational groups such as health care workers. This paper presents an overview of a number of vaccine-preventable diseases which occur in adults, and highlights the importance of immunization to protect those at risk of infection.
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.