BCG VACCINE

The BCG vaccine (Bacille Calmette Guérin) is a live virus vaccine prepared from attenuated strains of Mycobacterium Bovis. Use of BCG vaccine is recommended by the Expanded Programme on Immunizations of the World Health Organization for administration at birth and is currently used in more than 100 countries, including Guatemala. BCG vaccine is used to prevent disseminated and other life threatening manifestations of Tuberculosis in infants and young children. However BCG vaccine does not prevent infection with Mycobacterium Tuberculosis. The various BCG vaccines used throughout the World differ in compositor and efficacy.

Two big studies of Publisher clinical trials concluded that BCG vaccine has relatively high protective efficacy (around 80%) against meningeal and disseminated (called miliar) tuberculosis in children. The protective efficacy against pulmonary tuberculosis however is not as definite.

TUBERCULIN TESTING

The tuberculin skin test (TST) is the only practical tool for diagnosing Latent Tuberculosis infection in asymptomatic people. The test is recommended by the American Academy of Paediatrics fro children who are at increased risk of acquiring TB (Tuberculosis). Factor that have correlated consistently with increased risk of latent tuberculosis include recent contact with a case of TB, family history of TB, positive TST reactions n other current household members and foreign birth or prolonged travel to a country with high TB rates.

INTERPRETATION OF TST RESULTS IN PREVIOUS RECIPIENTS OF BCG VACCINE

Generally, interpretation of TST result in BCG recipients is the same as for people who have not received the BCG vaccine. Alter BCG vaccine immunizations, distinguishing between a positive TST result caused by Mycobacterium tuberculosis infection and that caused by the BCG vaccine can be difficult. The size of TST reaction (ie, induration) attributable to BCG immunization depends on many factors, including age at BCG immunization, quality and strain of BCG vaccine used, number of doses of BCG received, nutritional and immunologic status of the vaccine, recipient and frequency of TST administration.

Disease caused by Mycobacterium tuberculosis should be suspected strongly in any symptomatic person with a positive TST results, regardless of history of BCG immunization. When evaluation an asymptomatic child who has a positive TST result but who possible received BCG, verification of previous BCG immunization by written documentation or identification of the typical BCG immunization scar should be undertaken. Although a positive TST result never can be proven to be attributable to BCG vaccine, certain factors, such as documented receipt of several BCG immunizations, decrease the likelihood that the positive TST result is attributable to TB infection. Evidence that increases the probability that a positive TST result is due to infection includes known contact with a person with contagious TB, a family history of TB, immigration form a country with high prevalence of TB, along interval since the last dose of BCG (more than 5 years) and a TST reaction of more than 15mm..

Prompt radiologic evaluation of all children with a positive TST reaction is recommended, regardless of the child’s BCG immunization status. Chest radiographic findings of a granuloma, calcification or adenopathy can be causes by Mycobacterium tuberculosis but not by BCG immunization. I most situations, an asymptomatic BCG-immunized child with a positive TST result will have a normal chest radigraphy findings. For some children, such as recently immunized with BCG vaccine, children with documented multiple BCG immunizations or children who immigrated from a country with a low prevalence of TB, treatment may not be indicated. In Such cases follow up should include patient education and awareness of the signs and symptoms of tuberculosis disease.