3. A child's parents want to delay vaccination until their child is no longer breast-feeding. They are convinced that delaying the vac- cination schedule until at least three months after the child stops nursing is safe. Develop a professional and compassionate response to the parents to address their misconception. 4. At time point A, the patient's IgG titer against antigen X is 1:6; the patient's IgM titer to the same antigen is zero. Later, at time point B, the same patient encounters antigen X. The IgG titer to X is zero, and the IgM titer to X is 1:8. Describe a scenario that could explain these data.