Which of the following is an example of a contraindication to vaccination?

• A. Severe allergic reaction to a vaccine component or following a prior dose
• B. Mild fever
• C. History of seasonal allergies
• D. Past vaccine reaction that was minor

Answer: (A)

The main idea is recognizing conditions that make vaccination unsafe due to a high risk of a serious reaction. A severe allergic reaction to a vaccine component or to a previous dose is an absolute contraindication because giving the vaccine again could trigger life-threatening anaphylaxis. In contrast, a mild fever isn’t a contraindication; vaccination can often proceed when illness is mild, since delaying for every minor symptom would leave people unprotected. A history of seasonal allergies or a past vaccine reaction that was minor doesn’t prevent future vaccination, because these situations don’t indicate a dangerous risk from the vaccine itself. The key is weighing the risk of a severe allergic response against the benefits of protection, and a severe allergic reaction to a component or prior dose stands out as the reason vaccination would be withheld.