Final answer:
The variability of Maternally Derived Antibodies (MDA) in kittens leads to a vaccination schedule starting at 6 weeks of age and occurring every 3 to 4 weeks up to 16 weeks to minimize the window of susceptibility.
Step-by-step explanation:
The amount of Maternally Derived Antibodies (MDA) in a kitten at any one time point cannot be predicted because it varies depending on factors such as the amount and type of antibodies the mother has, the kitten's uptake of these antibodies, and their rate of natural decay. As a result, a series of vaccinations is administered to kittens every 3 to 4 weeks through 16 weeks of age in order to increase the chance that successful immunization will occur soon after the decline of MDA to sufficiently low titers. The series is started no sooner than 6 weeks of age, because neonates are more likely to develop vaccine organism-associated disease and may not respond well to vaccination. During administration of the series, a window exists when MDA concentrations are high enough to interfere with immunization but are not sufficient to prevent natural infection. This window of susceptibility can be minimized by strategically timing the vaccinations to ensure that they are administered as the MDA levels decline, without leaving a gap where the kitten is left vulnerable to diseases.