Anaphylactoid and/or hypersensitivity reactions might occur. Asplenic patients with lymphoid tumors who receive either chemotherapy or irradiation respond poorly. Use with caution in severely immunocompromised patients (e.g. patients receiving chemo/radiation therapy or other immunosuppressive therapy, including high-dose corticosteroids). Use in pediatric patients under 2 years of age usually not recommended. Packaging may contain natural latex rubber. Some dosage forms contain thimerosal.