From the Research
BCG granulomas typically form within 2-4 weeks after BCG vaccination. The formation of these granulomas is part of the normal immune response to the Bacillus Calmette-Guérin vaccine, which contains attenuated Mycobacterium bovis. Initially, the injection site may show redness and swelling within days of vaccination. This progresses to a papule in 1-2 weeks, which then develops into a pustule by 2-3 weeks. The pustule may ulcerate and drain before healing, leaving a small scar. The granuloma formation represents the cell-mediated immune response where macrophages, T lymphocytes, and other immune cells surround and contain the BCG organisms. This process is essential for developing immunity against tuberculosis. In some cases, the timeline may vary slightly depending on individual immune responses, with some granulomas appearing as early as 10 days or as late as 6 weeks post-vaccination, as reported in a case of granuloma annulare-like reaction to the BCG vaccination 1. Complications such as prolonged ulceration or lymphadenitis are rare but may occur in some individuals.
Some studies have reported various cutaneous complications of BCG vaccination, including granuloma annulare, foreign body granuloma, and lupus vulgaris 2, 3, 4. However, these complications are relatively rare and do not affect the overall timeline of granuloma formation. A review of the literature on skin complications of BCG vaccination highlights the importance of recognizing both anticipated and unexpected cutaneous findings 4. In general, the formation of BCG granulomas is a benign process that does not require treatment and is a necessary step in developing immunity against tuberculosis.
It is worth noting that the exact timeline of granuloma formation may vary depending on individual factors, such as immune response and vaccine strain. However, based on the available evidence, the typical timeframe for BCG granuloma formation is 2-4 weeks after vaccination, with some variations reported in the literature 5, 1.