BCG (Bacilles-Calmette-Guerin) vaccination, revaccination and chemoprophylaxis are worldwide methods of tuberculosis specific prevention. For vaccination and revaccination the BCG strain is used, it is harmless, has specificity, immunogenity, keeps residual virulence, has limited multiplication in vaccinated organism, being in lymphatic nodes. For immunization in Russian Federation a dry BCG vaccine is applied as most stable, and capable for enough time to keep required quantity alive MBT.
The duration and stability of post-vaccinated immunity is determined by character of immuno-morphological changes and vegetation of BCG strain in inoculated organism. BCG strain gets accustomed in organism vegetating in it, stimulating development of anti-tubercular immunity. In two weeks after BCG vaccination L-forms are begun to transform. In such situation MBT of BCG strain can exist in organism for a long time, maintain anti-tubercular immunity. The efficiency of BCG vaccinations is shown by the fact that among vaccinated and revaccinated children, teenagers and adults incidence of new tuberculosis cases and mortality rate is lower than among not vaccinated. The duration of post-vaccination immunity maintain during 5-7 years after intradermal BCG vaccination.
Application of a BCG vaccine and its dosing.
On territory of Russian Federation intradermal BCG vaccine vaccination is used as the most effective and economical method of vaccination. BCG vaccination of newborn is carried out on 4 – 7-th day of life without preliminary tuberculin test. BCG revaccination or repeated inoculation against tuberculosis will be carried out in decreed (approved) periods at presence of negative reaction on Mantoux test with 2 TU PPD-L. The first revaccination is carried out in the age of 7 years (1-st school class), second in 11-12 years (5-th school class), third – 16-17 years (10-th school class). Subsequent revaccinations will be carried out with an interval 5 – 7 years up to 30-years of age. Method of revaccination is the same at the vaccination.
Chemoprophylaxis.
The term chemoprophylaxis has been applied to two distinct types of preventive therapy of tuberculosis.
- Primary chemoprophylaxis where the drug is given to individuals who have not been infected (with negative tuberculin test) in order to prevent development of disease (e.g. infant being breastfed, being in contact with bacillary patient).
- Secondary chemoprophylaxis where the anti-tubercular drugs is used to prevent development of disease in people who have already been infected but being in condition of repeated infection or fall ill with tuberculosis.
The groups of populations eligible for chemoprophylaxis.
Chemoprophylaxis will be carried out for the prevention of susceptibility to tuberculosis in the following groups of the population:
- children, teenagers and adults who are being in constant contact with tuberculosis patients;
- healthy children without clinical signs, teenagers and persons of young age till 30 years of age, for the first time MBT infected;
- persons with constant hyper-allergic reactions on tuberculin;
- newborn (BCG vaccinated in the maternity house), born from the tubercular breast feeding mothers, whose disease was not revealed in time;
- person with newly positive tuberculin reactions;
- the persons with previous tuberculosis signs, at presence of the adverse factors (acute forms of diseases, operation, traumas, pregnancy etc.), capable to cause an aggravation of tuberculosis, and also persons, earlier treated from tuberculosis, with the large residual changes in lungs, being in a dangerous environment;
- the persons with signs of old tuberculosis but at presence they have concomitant diseases capable of causing activation of tuberculosis (diabetes, colagenosis, silicosis, sarcoidosis, ulcer of stomach, operation on a stomach etc.).
Among the persons, undergone chemoprophylaxis, the number of incidence of tuberculosis in 5-7 times is less in comparison with the appropriate groups of the persons, without chemoprohylaxis.
Drugs.
For chemoprophylaxis isoniazid or ftivasid are used during 3 month, and if epidemic danger remains chemoprophylaxis is repeated twice per year for 2-3 months. To the persons with hypersensitivity to tuberculin test prophylaxis is recommended with two preparations —isoniazid and pirazinamid (ethanbutol).
Doses.
For the adult and the teenagers the daily doze of isoniazid for every day administration 0,3 g., for children 8-10 mg/kg. If intolerance of isoniazid occurs, it is possible to use chemoprophylaxis with ftivasid. Ftivasid is prescribed for the adult 0,5 g twice per day, children 20-30 mg/kg. Both adults, and children should necessarily thus receive vitamins B6 and С.
The application of secondary chemoprophylaxis is most justified by seasonal courses (in a autumn-spring season) during 2-3 month twice per year.