Which of the following individuals should not receive the MMR vaccine?

The MMR vaccine, which protects against measles, mumps, and rubella, is a live attenuated vaccine. Therefore, there are specific circumstances where it is contraindicated, particularly in pregnant individuals.

During pregnancy, especially in the third trimester, administering live vaccines like MMR is not recommended due to the potential risk they could pose to the developing fetus. The immune response to the live vaccine may not be favorable, and there could be concerns regarding the vaccine's effect on fetal development. Thus, a 23-year-old woman in her third trimester should not receive the MMR vaccine.

Other groups mentioned may have considerations but do not have the same absolute contraindication. For instance, individuals with chronic conditions, though they might require careful assessment, could still receive the vaccine if the benefits outweigh the risks.