How can the skin test of BCG be successful if the ppd test of BCG is normal?

BCG vaccine is usually inoculated within 24 hours after birth, and then goes through a long process of redness, swelling, swelling, suppuration and scab, which takes 2-3 months. After three months of BCG vaccination, it is necessary to confirm whether BCG vaccination is successful or not, and ppd test is generally needed. So, how can the BCG skin test be successful? Pictures of normal ppd test of BCG?

BCG skin test is what we usually call tuberculin test, also called ppd test. Doctors can use this test to determine whether antibodies have been successfully produced in the body. The skin test of BCG vaccine is generally carried out with 5u pure tuberculin derivative, which will produce local red and swollen lumps within 48-72 hours. As long as the diameter of the swollen lump is more than 5mm and less than 20mm, then even if the inoculation is successful, if the diameter of the lump is less than 5mm, then it is not successful. At this time, it is necessary to replant BCG.

Usually, the skin test is carried out three months after the baby is vaccinated with BCG, so parents must not forget the time. Some parents think that BCG vaccination is successful as long as the baby's arm goes through the process of redness, pus and scab, so they don't do skin test review. In fact, this process will not happen to every child, nor does it mean that BCG vaccination is successful. It is more accurate to do ppd test.