What is the cause of pus oozing out from the BCG vaccination site?

Q: Our newborn was given the BCG vaccine after her birth. A week later, she developed a pus mark on the spot of the vaccination. The pus was oozing so we squeezed/extracted the remaining pus from the sore and cleaned it with alcohol. Our paediatrician told us that we should not have done that. We are worried whether the vaccine will be effective anymore or not. Did we do any harm to our baby by extracting the pus?

A:The child will need to be examined to give a categorical reply. It is important to evaluate if some other infection has caused the pus, or whether it is related to a rare side effect of the BCG vaccine (see for lymph node enlargement in the axilla). The treatment for both is different, and also depends upon whether the pus is draining now or not.