You can see if you have a bumpy scar on your left upper arm, which is the mark left by the BCG vaccination. Does it mean that you can rest easy after BCG vaccination? The protective power of BCG vaccine is actually controversial in the academic field. According to clinical statistics, the number of people who have been vaccinated with BCG vaccine who have tuberculous meningitis and blood-borne tuberculosis is indeed very small, but it does not change the chance of getting tuberculosis, for example, there is still a possibility of being infected after contacting patients with positive sputum smears. Therefore, it is not safe to assume that the BCG vaccination is a guarantee. The cure rate for tuberculosis in China has improved a lot compared to the past, with the cure rate for primary treatment (the first visit to the hospital) reaching more than 90% and even 98%, and the recurrence rate has also dropped to less than 3%. However, the number of TB cases is still high, and China is one of the 22 countries with a high burden of TB worldwide, with the second highest number of TB cases in the world. In addition, there are many potential TB patients, that is, people who have been infected with TB bacteria but have not yet developed the disease; the reason they have not developed the disease is that their own resistance is so strong that they do not even show symptoms; but not developing the disease now does not mean that they will not develop it in the future. People who have already been exposed to TB patients, the elderly or people with chronic diseases whose immunity is on the decline, as well as students and migrant workers who have to live in groups, should go to the hospital for PPD skin testing. The stronger the PPD skin test reaction, the greater the likelihood of TB infection, and a strong positive PPD skin test means that the patient has been infected with TB. The reaction time is usually at least one month, and elderly people often do not react to the skin test, so it is recommended to take a chest X-ray or sputum test. Usually a negative PPD skin test after BCG vaccination indicates a failure of vaccination. Patients with low immunity are also advised to go to the hospital to test for TB infection, for example, in the case of AIDS patients, the hospital can help to do the test for free. If you have been in contact with infectious TB patients, you can tell your doctor and the designated hospital will provide a free chest X-ray examination.