It is commonly asserted that the sub-Saharan African HIV/AIDS epidemic is predominantly due to heterosexual transmission. However, recent re-examination of the available evidence strongly suggests that unsafe health care is the more likely vector. The present report adds to the evidence for health-care transmission by showing that Kenyan women who received prophylactic tetanus toxoid injections during pregnancy are 1.89 times (95% confidence interval [CI]:1.03–3.47) more likely to be HIV-1 seropositive than women who did not receive this vaccination. In contrast, recent sexual behaviour (condom use, number of partners) was not related to HIV status. The findings are unconfounded by reverse causality (all injections were purely prophylactic rather than for treatment of any HIV-related illnesses, and none of the women reported knowing that she was HIV seropositive). Focus on a specific injection may have improved participant recall. The results are consistent with health care being a very important vector for HIV in sub-Saharan Africa. It is recommended that there be a reallocation of resources to address healthcare transmission of HIV/AIDS