A 13-month-old child receives the first dose of varicella vaccine today. The parents want MMR vaccine given at the same visit, but it is unavailable in the clinic. When can the MMR be administered at the earliest?
- A Any time after 2 weeks
- B After a minimum interval of 4 weeks ✓
- C After a minimum interval of 8 weeks
- D After 3 months, to avoid interference
Correct answer: B. After a minimum interval of 4 weeks
Explanation
If two live parenteral vaccines are not administered on the same day, they must be separated by at least 28 days (4 weeks), because a live vaccine given earlier induces interferon responses that blunt replication of the subsequently injected live vaccine. Two-week separation risks failure of seroconversion, while intervals of 8 weeks or more are unnecessary delays that leave the child unprotected longer.
Reference: AAP Red Book: Report of the Committee on Infectious Diseases, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.