What type of reactions may occur as a hypersensitivity response to the Hepatitis B vaccine?

Hypersensitivity reactions to vaccines, including the Hepatitis B vaccine, can manifest as allergic responses. Urticaria, commonly known as hives, and anaphylaxis are specific immune system reactions that can occur when an individual has an allergy to components present in a vaccine, which may prompt the body to react inappropriately.

Urticaria involves the development of itchy, raised welts on the skin, while anaphylaxis is a severe, life-threatening reaction that can cause difficulty breathing, swelling of the throat, rapid heartbeat, and even a drop in blood pressure. These reactions are part of the spectrum of hypersensitivity responses and can happen shortly after vaccination.

In contrast, fatigue and dizziness, severe headaches, and nausea and vomiting may be observed as side effects from the vaccine but do not reflect the immediate immune system responses that classify as hypersensitivity reactions. These symptoms are typically more common and do not involve the immune system's allergy pathway, which is why they are not categorized with urticaria or anaphylaxis. Thus, the recognition of urticaria and anaphylaxis as potential hypersensitivity reactions is critical for patient safety and monitoring after vaccination.