Final answer:
The best response by the nurse is to inform the parents that the child should receive the second dose of the MMR vaccine in the next week to maintain the catch-up schedule recommended by the CDC.
Step-by-step explanation:
The nurse in a pediatric clinic notices a preschool client is on a delayed immunization schedule for the measles, mumps, and rubella (MMR) vaccine. Since it has only been 3 weeks since the initial administration, the best response by the nurse would be to call the parents and explain that the child will need to be seen in the next week to receive the second dose of the MMR vaccine to stay on schedule. This aligns with the CDC's catch-up immunization schedule, which recommends a second dose of the MMR vaccine for optimal protection against these diseases. It's important to refute any misinformation regarding vaccines, such as the debunked claim that the MMR vaccine causes autism, and emphasize the importance of following the recommended schedule to maintain public health and prevent outbreaks.