Which of the following medications is NOT recommended for discomfort after vaccination?

Aspirin is not recommended for discomfort after vaccination, particularly in children and adolescents. This recommendation is primarily due to the risk of Reye's syndrome, a rare but serious condition that can cause severe liver damage and neurological complications. Reye's syndrome has been associated with the use of aspirin in individuals under the age of 19 during viral infections, including those that may occur after vaccination.

On the other hand, ibuprofen and acetaminophen (which is also known by the brand name Tylenol) are commonly used to alleviate discomfort following vaccinations. They can help manage fever and pain without posing the same risks associated with aspirin. Therefore, the choice of aspirin as a medication for post-vaccination discomfort is not advisable, distinguishing it clearly as the option that is not recommended.