Why is the tuberculosis vaccine not routinely offered to patients?

There are a few reasons why the tuberculosis (TB) vaccine is not routinely offered to patients in all countries:

1. Risk of exposure: Not all individuals are at the same risk of being exposed to TB bacteria, and vaccination may not be necessary for those at low risk. Tuberculosis is more prevalent in certain areas or populations with factors like overcrowding, poor hygiene, and malnutrition, so vaccination efforts are often targeted towards those regions or vulnerable groups.

2. BCG vaccine efficacy: The Bacillus Calmette-Guérin (BCG) vaccine, the most commonly used TB vaccine, provides variable protection against TB. While it has been effective in preventing severe forms of TB, such as childhood TB meningitis and miliary TB, its overall effectiveness against pulmonary TB in adults varies and is about 50-60%.

3. Duration of immunity: BCG vaccination provides immunity for a limited duration, typically 10 to 15 years, after which the protective effect may decline. However, the exact duration of protection is not well-established. This necessitates repeated vaccination in countries with high TB incidence, which can be logistically challenging and resource-intensive.

4. Contraindications and adverse reactions: BCG vaccine is contraindicated in certain individuals, such as those with severe immunodeficiencies, positive tuberculin skin tests, or known or suspected HIV infection. Additionally, some people may experience adverse reactions to the vaccine, such as local inflammation or tenderness at the injection site, fever, or lymphadenopathy.

5. Cost-effectiveness: The decision to include BCG vaccination in a routine immunization program is often based on cost-effectiveness considerations. In some countries with a relatively low incidence of TB and limited resources, the cost of vaccination may outweigh the benefits, especially for those considered to be at low risk of exposure.

Based on these factors, many countries have different policies when it comes to tuberculosis vaccination, considering factors like the local TB epidemiology, vaccination costs and benefits, and priorities in public health spending. In some countries, the TB vaccine is offered to certain high-risk groups, such as healthcare workers, children in high-incidence areas, or individuals in close contact with TB patients.