This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
A neonate following BCG vaccination developed a side effect. Which of the following side effect would the neonate most likely develop after vaccination? 
Select and explain. 
A. Fever, B. Ulceration, C. Osteomyelitis, D. Regional lymphadenitis
B: Ulceration
Answer: B: Ulceration 
Explanation: Ulceration is the most common side effect post BCG vaccination. Following vaccination, the local tissue response begins in 2-3 weeks, with scar formation and healing within 3 months. Side effects most commonly are ulceration at the vaccination site and regional lymphadenitis. Some vaccine strains also rarely cause osteomyelitis. In immunocompromised states, disseminated BCG infection can occur. Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition