Live attenuated vaccines are contraindicated in:
Live attenuated vaccines contraindicated in immunocompromised individuals because control of limited replication depends on intact innate and adaptive immune compartments. Immunocompromise includes congenital severe combined immunodeficiency affecting T cells, chronic granulomatous disease phagocyte defect, HIV with CD4 count below 200 cells per microliter in adults or below 15 percent in children, chemotherapy causing neutropenia, high dose systemic corticosteroids more than 2 mg per kg prednisone for 2 weeks, biologic agents anti TNF monoclonal antibodies, organ transplant recipients receiving calcineurin inhibitors tacrolimus suppressing T cell activation. In such hosts even attenuated strains can cause uncontrolled replication resulting in disseminated BCGitis with hepatosplenic granulomas after BCG, progressive vaccinia with necrotic lesions after smallpox vaccine, vaccine associated paralytic polio due to persistent poliovirus excretion and reversion, severe varicella from Oka vaccine. Pregnancy also contraindication due to potential fetal infection although risk theoretical. Therefore guidelines WHO advise use of inactivated, toxoid, subunit, conjugate, mRNA vaccines in immunocompromised which cannot replicate. Screening via HIV testing, medication history before live vaccine essential to avoid iatrogenic infection.
Ref: CDC Contraindications immunocompromised live; Plotkin Immunocompromised host; Red Book AAP.