Saturday, September 07, 2013

What is the normal reaction after getting the BCG vaccination?

Question: What is the normal reaction after getting the BCG vaccination?
Answer: Children in India are routinely given BCG at birth. 
In the individuals previously uninfected by M.tuberculosis, about 2 to 4 weeks after the 
vaccination, erythema around an area of induration appears. Approximately at the site of prick 
of injection a nodule shows up. Within 3 to 10 days time, it softens giving rise to a pustule. 
Bursting of the pustule in about 2 to 5 days after its appearance results in an ulcer 4 to 8 mm 
in size. This painless depressed ulcer with undermined edges is soon covered by a thin crust 
or scab, which tends to peel off at the slightest provocation. The healing of ulcer in to a 
depressed, thin, shining scar with undermined edges in 4 to 6 weeks of its formation, marks 
the uneventful termination of sequence of occurrences at the site of BCG vaccination. 
In an individual previously infected with Mycobacteria, exaggerated and accelerated reaction of 
similar nature as described above, is seen. The reaction in this case starts within hours after 
vaccination and ulcer, 6 to 12 mm in size, occurs within a week. Ulcer also heals into the scar 
earlier. Size of the erythema, induration, nodule, pustule, ulcer and scar all are bigger than 
those in the uninfected. 
Similarly a repeat BCG vaccination also results in bigger local reactions. They are, however, 
smaller than those in the infected individuals. Onset of reaction in them, is almost similar to the 

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