Final answer:
The nurse should plan to administer the Diphtheria, tetanus, and pertussis (DTaP) vaccine last when preparing to administer immunizations to a toddler.
Step-by-step explanation:
The nurse should plan to administer the Diphtheria, tetanus, and pertussis (DTaP) vaccine last when preparing to administer immunizations to a toddler. This is because the DTaP vaccine can cause local redness, swelling, or soreness at the injection site, which may negatively affect the placement or interpretation of other tests or vaccines. By administering the DTaP vaccine last, the nurse can minimize the risk of interference or confusion with other immunizations or tests.