Controversies in chicken-pox immunization.

Chicken-pox is one more newer vaccine in our armamentarium against infectious diseases. Due to its extremely contagious nature, varicella is experienced by almost every child or young adult in the world. Each year from 1990 to 1994, prior to availability of varicella vaccine, about 4 million cases of varicella occurred in the United States. Of these cases approximately 10,000 required hospitalization and 100 died. Although varicella is not commonly perceived as an important public health problem, the socioeconomic consequences in industrialized countries of a disease that affects practically every child and causes the carrier absence from work should not be underestimated. The varicella vaccines available in the market are safe and effective. A recent cost-benefit analysis in USA showed that routine chicken-pox vaccination is likely to save five times the investment. Even when only direct costs were considered, benefits almost balanced the costs. At present similar studies from developing countries are not available. The public health impact of varicella and zoster may be increasing in regions with high endemic rates of HIV infection. Varicella vaccine may be used either at an individual level to protect susceptible adolescents and adults, or at a population level, to cover all children as part of a national immunization programme. Vaccination of adolescents and adults will protect at-risk individuals, but will not have a significant impact on the epidemiology of the disease on a population basis. On the other hand, extensive use as a routine vaccine in children will have a significant impact on the epidemiology of the disease. If sustained high coverage can be achieved, the disease may virtually disappear. If only partial coverage can be obtained, the epidemiology may shift, leading to an increase in the number of cases in older children and adults. Hence, routine childhood varicella immunization programmes should emphasize high, sustained coverage. At present, this vaccine will have a lower priority in the National Immunization Schedule that does not have MMR and typhoid, which have a greater socioeconomic impact. Hence, at the present time WHO does not recommend the inclusion of varicella vaccination into the routine immunization programmes of developing countries.