Bullous pemphigoid (BP) typically affects the elderly. There are at least 40 reported cases of BP in childhood, 10 reported cases at 1 year of age or younger. The antigen of this autoimmune disease is localized to the hemidesmosome. Neoplasia, recurrent trauma, some systemic diseases, and psoriasis were previously reported as possible triggering factors of bullous pemphigoid in some cases. In the last 5 years, 10 adult and 2 infantile BP cases with a close relation of vaccination have been reported. Anti-influenza vaccine, tetanus toxoid booster, and tetracoq vaccine were the possible causes of these cases. We report herein a 3.5-month-old BP case in whom the lesions developed 24 hours after the first tetracoq vaccine. We suggest that vaccination may be the triggering factor of BP of any age by stimulating the immune system with an unexplained mechanism. (J Am Acad Dermatol 2001;44:348-50.)