The Bacillus Calmette-Guérin (BCG) vaccine is a live attenuated Mycobacterium bovis vaccine administered within the first few days of life in most countries to prevent childhood tuberculous meningitis and miliary disease. With more than 3 billion people having received it, it is the most widely used vaccine worldwide [30]. It is not generally recommended for use in the United States due to a relatively low prevalence of tuberculosis and the variable effectiveness of immunization against adult pulmonary tuberculosis.
In general, the BCG vaccine exhibits an excellent safety profile. The main adverse events to vaccination are local reactions, including scarring (up to 92% of healthy neonates), pustule formation and drainage [31]. These usually respond to conservative management. Axillary and cervical lymphadenopathy are the most common regional adverse effects, and may persist for a few months, occasionally resulting in surgical drainage [32]. Disseminated BCG infection is a rare complication, occurring in less than one per million individuals. It has been reported in children with congenital immune disorders, such as severe combined immunodeficiency, chronic granulomatous disease, and the acquired immunodeficiency syndrome. About half of the cases of disseminated BCG infection in children are linked to rare immunodeficiencies of the IFN-γ and IL-12 pathways [33], including a report of fatal BCG infection in an infant with IFN-γ-receptor deficiency [34]. A relatively high incidence of osteitis, osteomyelitis and disseminated BCG infection was noted upon use of the Danish 1331 BCG vaccine strain manufactured by Statens Serum Institut, involving several hundreds of children in Finland between 2000 and 2006. Retrospective analysis suggested that the increased reporting rate, although within the expected frequency of adverse reactions expected for the product, might be due to a combination of factors including heightened awareness surrounding use of the newly available BCG Vaccine SSI following publicity associated with the withdrawal of the previously used product, the relatively higher potency/reactogenicity of the Danish 1331 strain, and administration errors (incorrect dose or route of administration) [35, 36]. The low and declining rate of tuberculosis in Finland, prompted a change in vaccination policy in Finland from universal to risk-group targeting [37].