An 18-year-old female receives a booster dose of MMR; which precaution is appropriate?

• A. She should not become pregnant within the next 4 weeks
• B. She can become pregnant immediately
• C. She should delay MMR until after pregnancy
• D. Pregnancy status doesn't matter

Answer: (A)

Live vaccines, like MMR, are live attenuated vaccines and carry a precaution to avoid conceiving for a short period after vaccination. After a booster dose of MMR, the recommended precaution is to refrain from pregnancy for 28 days. This window helps prevent any theoretical risk to a developing fetus from the live vaccine virus. Since she just received the booster, the appropriate instruction is to not become pregnant in the next four weeks.

If she were already pregnant, MMR is generally avoided. The other statements don’t fit: becoming pregnant immediately isn’t advised after MMR, delaying vaccination until after pregnancy isn’t the standard precaution in this scenario, and pregnancy status does matter with live vaccines.