Are there side effects of the flu vaccine?

Generally, influenza vaccines may have side effects, but these are mostly mild and transient local or systemic reactions. Severe side effects are extremely rare, and the overall safety profile is high. There is no need to refuse vaccination due to concerns about side effects. The details are as follows:

In terms of side effect types, they can be divided into common mild reactions and rare severe reactions. Common mild reactions are primarily local, such as redness, pain, and induration at the injection site, which usually resolve spontaneously within 1–2 days. Systemic reactions are less common and may include low-grade fever, fatigue, headache, and muscle aches, typically lasting 1–3 days and requiring no special treatment. These responses are normal signs of the body's immune system reacting to the vaccine, not actual illness.

Severe side effects are extremely rare and mainly include severe allergic reactions and Guillain-Barré syndrome. The incidence of severe allergic reactions is approximately 1 per million doses, while Guillain-Barré syndrome occurs in about 1–2 per million doses. These serious events are often associated with specific vaccine types or individual allergic predispositions. Immediate medical attention is required if they occur, but risks can be further reduced through pre-vaccination health screening.

The risk of side effects from the flu vaccine is far lower than the health risks posed by influenza itself. Individuals who meet vaccination criteria should prioritize getting vaccinated. If unusual symptoms such as persistent high fever or severe rashes occur after vaccination, prompt medical evaluation is recommended, though excessive concern is unnecessary.