Which of the following is a potential severe allergic reaction to vaccines?

Anaphylaxis is a severe, potentially life-threatening allergic reaction that can occur after vaccination. It is characterized by rapid onset of symptoms that may include difficulty breathing, swelling of the throat or tongue, hives, and a significant drop in blood pressure. While these reactions are rare, they are serious and require immediate medical attention, often involving the administration of epinephrine.

The other symptoms listed, such as fever, nausea, and headache, are common, mild side effects that can occur after vaccination but are not classified as severe allergic reactions. They generally resolve on their own and do not pose a significant risk to the individual’s health. Understanding the distinction between these different types of reactions is important for recognizing when immediate medical intervention might be necessary.