Bacille Calmette-Guerin (BCG), a live attenuated Mycobacterium bovis vaccine, poses a risk to human immunodeficiency virus (HIV)-infected children; this risk has not been well quantified. We estimate the risk of disseminated BCG disease in HIV-infected children in a setting highly endemic for tuberculosis and HIV.

We conducted a prospective hospital-based surveillance study in the Western Cape Province, South Africa. Clinical and laboratory-confirmed cases of disseminated BCG disease in children <1 year of age from January 2002 to December 2004 at a referral hospital were used as numerator data. Denominator data for calculations of disseminated BCG risk were obtained through estimating the total number of HIV-infected infants receiving BCG based on the known vaccination coverage in the study setting, combined with population data on the total number of children <1 year of age, the known HIV prevalence amongst women attending public antenatal care facilities and different scenarios (5–15%) for the rate of vertical HIV transmission.

Nine cases of disseminated BCG disease were identified over the study period, seven of these were in HIV-infected infants. The estimated risk for HIV-infected infants to develop disseminated BCG disease, given a 95% BCG coverage and an HIV prevalence of 12.4–15.4% amongst women, were as follows for different scenarios of vertical HIV transmission: 329–417/100,000 vaccinees (assuming 5% vertical HIV transmission), 164–208/100,000 vaccinees (assuming 10% vertical HIV transmission) and 110–139/100,000 vaccinees (assuming 15% vertical HIV transmission).

The risk of disseminated BCG disease is increased several hundred fold in HIV-infected infants compared to the documented risk in HIV-uninfected infants. Data on the protective effect of BCG in HIV-exposed and infected children is lacking. Population- and hospital-based surveillance is vitally important to more accurately estimate the safety and benefits of BCG in HIV-exposed and infected infants.