Question
The BCG vaccination was administered on January 11th, and I only noticed the pus-filled blister yesterday. There were no symptoms before that. Is it normal for this blister to appear two months later?
Answer
Generally, after newborns are vaccinated with the BCG vaccine on the second day of life, they can produce effective immunity within 2 to 3 months. The regional reactions after BCG vaccination are different from those of other vaccines. Most children will experience a regional reaction again 3 to 4 weeks (initial vaccination) or 1 to 2 weeks (revaccination) after receiving the BCG vaccine, which goes through a process of redness, swelling, pustule formation, ulceration, and scabbing. Typically, scabs form around 3 months and regional scars are formed. This is a normal reaction process after BCG vaccination and indicates an effective vaccination. If this reaction does not occur again, it may suggest a successful vaccination and a booster dose might be considered. To predict the success of the BCG vaccination, a tuberculin (OT) test can be conducted at the local tuberculosis prevention and treatment center 8 to 14 weeks after vaccination, with a normal regional reaction being a redness of 0.5 to 1.0 centimeters.