From the Guidelines
The BCG vaccine can cause several potential complications, though serious adverse events are rare, and individuals with compromised immune systems face higher risks of serious complications. Most commonly, patients experience localized reactions at the injection site including redness, swelling, and the formation of a small ulcer that typically heals within 2-3 months, often leaving a small scar, as noted in 1. Some individuals may develop enlarged lymph nodes (lymphadenopathy) near the injection site, which usually resolves without treatment. Fever is another common side effect that typically subsides within 24-48 hours. More serious but rare complications include:
- Abscess formation at the injection site
- Disseminated BCG infection (occurring in approximately 1 in a million cases) 1
- Osteitis (bone inflammation), which typically develops 4 months to 2 years after vaccination 1 These complications occur because BCG contains live attenuated Mycobacterium bovis bacteria, which can cause localized or systemic infections, particularly in those with weakened immune systems. It is crucial to contraindicate the BCG vaccine in people with primary or secondary immunodeficiencies, including HIV infection, as stated in 1 and 1, to prevent severe complications. If severe reactions occur, treatment with anti-tuberculosis drugs like isoniazid may be necessary. The risk of fatal disseminated BCG disease, although rare, underscores the importance of careful consideration before administering the vaccine, especially to immunocompromised individuals 1.
From the Research
Potential Complications of the BCG Vaccine
The BCG vaccine, like any other vaccine, can cause complications in some individuals. These complications can range from mild to severe and can be localized or disseminated.
Localized Complications
- Hypersensitivity reactions, abscesses at the injection site, and localized lymphadenopathy are common localized complications of the BCG vaccine 2.
- These complications are usually self-limiting and can be managed with drainage and chemotherapy with isoniazid or erythromycin 2.
- Injection site reactions and non-suppurative lymphadenitis can be managed conservatively, with good outcomes 3.
Disseminated Complications
- Disseminated disease can occur in people with impaired immunity, and it is often fatal 2.
- BCG should never be given to people who are known to be infected with HIV, but the risk of complications in children born to HIV-infected mothers is low 2.
- Disseminated disease can also result from intravesical instillation of BCG to treat bladder cancer, but this responds to antituberculosis chemotherapy 2.
- Severe combined immunodeficiency is the most common primary immunodeficiency disease associated with BCG vaccine complications, and it also shows the highest BCG-related mortality 4.
Management and Outcome
- The management of BCG complications varies between clinicians, and the optimal approach remains uncertain 3.
- The majority of children with injection site reactions can be managed conservatively, with complete resolution within 6 months 3.
- Children with lymphadenitis may require anti-tuberculous therapy and/or a procedure, and the outcome can vary 3.
- Patients with primary immunodeficiency diseases are prone to develop vaccine-derived complications, and systemic neonatal PID screening programs may help to prevent a substantial amount of BCG vaccination complications 4.
Risk Factors
- The frequency of adverse effects is inversely related to age at vaccination 5.
- The vaccine can cause severe disseminated BCG infection, especially in subjects with congenital or acquired immunodeficiency (notably HIV infection and immunosuppressive therapy) 5.
- The risk of adverse effects can be minimized by avoiding patients with contraindications and by careful administration 5.