The correct answer is administration of vaccination.
DTaP refers to a vaccine, which assists the younger children below the age of 7 to develop immunity against the three dreadful ailments caused by bacteria, like tetanus, diphtheria, and whooping cough.
Mild fever after the DTaP vaccine is not unusual, thus, the vaccination should not be withheld for that reason. However, vaccination can be withheld in case of previous anaphylactic sensitivity or reaction to a component in the vaccination.
To prevent cells from either shrinking or swelling you should keep them in an isotonic solution. Isotonic solution is a solution with equal amount of solute and solvent. Therefore, when cells are placed in such a solution they will not lose or gain water, as opposed to hypertonic (more solute than solvent) and hypotonic (more solvent than solute) solutions.