For a 15-month-old toddler, who is being treated for acute lymphoid leukemia, there are vaccines contraindicated, especially if the child undergoing chemotherapy. For example, live vaccines such as varicella, oral polio, measles-mumps-rubella (MMR) and bacillus Calmette-Guérin (BCG) should not be given to children under chemo. Although, inactive vaccines may be fine but active vaccines should not be administered.