BCG vaccine, a type of vaccine, is given to children at birth to prevent the occurrence of tuberculosis. However, some parents report that there is no BCG scar on their child’s arm, does this mean that the vaccination was not successful? The BCG vaccination time The BCG vaccination time is usually performed within 24 hours of the baby’s birth, and the vaccination site is the outer part of the deltoid muscle of the upper arm. The Ministry of Health stipulates that babies who have not received BCG vaccination can be replenished directly if they are less than 3 months old; if they are between 3 months and 3 years old, a tuberculin (PPD) test should be performed and a negative result will allow them to be replenished; babies 4 years old and older will not be replenished. If the average diameter of local redness at the injection site of BCG vaccine is 5-10 mm, it is a normal strong positive phenomenon, which means that BCG vaccination is successful, but if there is no local redness or redness <5 mm, it is negative, which means that the vaccination may not be successful and the vaccine is not alive in the body, so you should go for a review of BCG vaccination and timely replanting. If no reaction has occurred by 3 months after vaccination, it is likely that the vaccination has failed. At this time, a tuberculin (PPD) test is performed to conclude whether the vaccination was successful by intradermal injection and observation of the local reaction. If the site of PPD injection has only needle-eye size traces and no hard nodules, it is a negative reaction, indicating no effect of BCG vaccination; if there is redness and swelling and hard nodules of about 5-10 mm in diameter, it is a positive reaction, indicating successful BCG vaccination. People who cannot be vaccinated with BCG 1. People who are suspected of having tuberculosis or are suspected of being infected with tuberculosis should first undergo a tuberculin test to determine that they are not infected with tuberculosis, that is, a negative tuberculin test, before they can be vaccinated with BCG; 2. People suffering from acute fever, fever, skin diseases, severe eczema, chronic diseases, acute infectious diseases and premature babies or newborns weighing less than 2500 grams should not be vaccinated for the time being BCG vaccine should not be given to people with congenital or acquired immune deficiency.