BCG vaccination in India and tuberculosis in children: newer facets

Abstract

With the extended programme of immunisation and since 1985 the universal programme of immunisation and the coverage status of BCG vaccination in India has been very good, although it is still unsatisfactory in the eastern states. It is emphasized that BCG vaccination cannot prevent natural tuberculous infection of the lungs and its local complications, although it reduces the haematogenous complications of primary infection. However, this is not true for malnourished children who, inspite of BCG vaccination, develop serious, and often fatal types of tuberculosis such as miliary, meningitic and disseminated tuberculosis. The tuberculin anergy in malnourished children, is mainly responsible for high morbidity and mortality. BCG vaccinated, well-nourished children manifest modified patterns of tuberculous disease, following infection. The most important manifestation is the increased incidence of intrathoracic tuberculosis, specially enlargement of the various groups of mediastinal nodes and their local complications. Localisation of the disease by T cell immunity, due to BCG vaccination is responsible for this and the much lower incidence of haemotological complications such as neurotuberculosis and disseminated disease. In these children, the clinical picture of neurotuberculosis is also modified, with a tendency for more localised involvement of the brain and meninges. Similarly, vaccinated children may present with hepatomegaly, splenomegaly or isolated organ disease. It is important to relearn the new patterns of tuberculosis disease seen in vaccinated, non-malnourished children, and to a lesser extent in children with grade 1 to 2 protein energy malnutrition (PEM). With these limitations of BCG vaccination, other strategies like chemoprophylaxis need multicentric trials in high risk children, in different parts of the country.

PIP: Tuberculosis is a major global public health problem with 8 million new cases of pulmonary tuberculosis in the world per year and 2.89 million deaths. In India in 1989, the approximate morbidity of tuberculosis was 2%, i.e., there were 15 million cases of pulmonary tuberculosis. Of these 25% were sputum positive, posing a serious threat of transmitting the infection to children. Of the 4 million infectious patients, over 1 million would be considered as chronic or relapsing cases who have been partially treated. The Indian National Tuberculosis Program (NTP) has now completed 25 years. Every year, 1 million new cases of adult tuberculosis are detected. 70% of these patients do not complete standard regimens and 45% do not complete short course regimens. In 1983 about 80.71 million children under 16 years old in India were infected. In a survey carried out in 1990 in urban and rural areas of Delhi, BCG vaccination coverage was 90% in the urban and 84.7% in the rural areas. Impact of BCG vaccination has demonstrated that classical or generalized tuberculosis meningitis, miliary TB, disseminated tuberculosis, and other serious complications of primary infections go on occurring in malnourished BCG-vaccinated children. The variable efficacy of the present BCG vaccine observed in different prospective human trials has shown the necessity of conducting research of immunoregulatory mechanisms, and developing newer vaccines for global control of tuberculosis. Other topics include immune responses to the present BCG vaccine (cellular immunity, macrophage, T-lymphocytes); BCG vaccination and tuberculin test; BCG vaccination by nebulization (aerosol BCG vaccine) by the respiratory route; a booster dose of BCG vaccine in the preschool period; protein energy malnutrition and delayed hypersensitivity reaction; BCG test in non-vaccinated and vaccinated children; HIV infections or their symptoms as a contraindication to BCG vaccination; and BCG lymphadenitis in children (7% in seropositive HIV children).