Vaccine BCG is not a lifelong immunity

Vaccine BCG is not a lifelong immunity. Firstly, the duration of BCG is about 20 years. BCG is usually vaccinated once at birth, and a scar will be left, indicating successful vaccination. If there is no scar on the baby's arm, it means that the vaccination was not successful, and a booster dose is needed. The duration of BCG is not yet clear, but it is generally believed that the protection level will decline year by year, reaching an insignificant level after 10 to 20 years.

Secondly, the role of BCG in preventing tuberculosis should also focus on the cultivation of hygiene habits, not just relying on vaccines. BCG cannot prevent the reactivation of latent tuberculosis, which is the main source of infection for the spread of Mycobacterium tuberculosis in the population. Therefore, BCG cannot affect the spread of tuberculosis, and there is little significance for adults to receive BCG again.

Thirdly, what are the reactions after BCG vaccination? 1. Common local reactions include redness and swelling at the injection site 2-3 weeks after vaccination, with the formation of a papular hard lump with an average diameter of about 10mm. Gradually, it softens into a white pustule, which ruptures spontaneously. Most of them heal after 8-12 weeks, and a slightly concave scar (ie BCG scar) is formed locally after the scab falls off. The whole process lasts for 2-3 months. Generally, there is no systemic reaction, but a few people may have mild enlargement of the axillary lymph nodes on the vaccinated side (or on the clavicle in a few cases) within 1-3 months after vaccination, but it does not exceed 10mm, and sometimes ruptures and becomes purulent. 2. Rare reactions include severe rash, purpura, shock, and other abnormal reactions in a very few people after BCG vaccination, and they should seek medical attention promptly. 3. Occasionally, the following reactions may occur during vaccination: (1) Lymphadenitis: about 1-2 months after vaccination, lymphadenitis may occur in the neck, axilla, upper and lower clavicle, etc., with lymph node enlargement (greater than 1.0cm). In those with strong reactions, the lymphadenitis is obvious, which may form abscess or rupture, or have small abscesses at the injection site. The reaction is often stronger in those receiving intradermal injection than in those receiving scratch method. In addition, those with positive old tuberculin (OT) test may also have a strong reaction after vaccination. (2) Lupus-like reaction: It is related to the residual virulence of the tuberculosis strain. (3) Scar: Scar protrusions are formed due to abundant granulation tissue, sometimes presenting as keloid, which is more common in those who receive direct scratch vaccination without OT test. Currently, the duration of BCG is not particularly clear. It is generally believed that its effect will become less significant after 20 years. However, we don't need to worry too much. The risk of tuberculosis after BCG vaccination will be greatly reduced. If BCG vaccination is not successful, a booster dose should be given.