Fever after receiving inactivated hepatitis A vaccine

Fever, also known as pyrexia, following hepatitis A inactivated vaccination is usually caused by vaccine reaction or allergy. Targeted management should be based on the specific cause. The details are as follows:

1. Vaccine Reaction

The hepatitis A inactivated vaccine stimulates the human immune system and activates immune cells after injection. To combat the perceived threat, immune cells secrete cytokines such as interleukins and interferons. These cytokines are pyrogenic—they act on the hypothalamic temperature regulation center, raising the body's temperature set point, which leads to an imbalance between heat production and dissipation, ultimately resulting in fever. This is a normal response and generally not a cause for concern. Close observation of symptoms is recommended.

2. Allergic Reaction

If the individual has a hypersensitive constitution and is allergic to the hepatitis A inactivated vaccine, an allergic reaction may occur after vaccination, presenting with fever along with local skin rashes, itching, and other symptoms. In such cases, patients should take antihistamine medications such as levocetirizine hydrochloride tablets or loratadine tablets under medical guidance.

It is recommended that individuals monitor their symptoms closely after vaccination. If any discomfort occurs, they should promptly inform their healthcare provider and seek timely treatment to avoid delays in managing potential complications.