What Should You Know About Flu Shot Symptoms?

Flu shot symptoms are usually mild and short-lived, such as soreness at the injection site, tiredness, headache, or a low fever. These effects reflect your immune system responding to the vaccine and do not mean that the injection has given you influenza. Some people have no noticeable symptoms at all.

The arm may feel tender, warm, or slightly swollen where the needle went in. You may also feel achy, sleepy, or generally under the weather for a short time. These reactions often begin soon after vaccination and settle as your immune response calms. A flu vaccine cannot cause influenza because the injected vaccine does not contain a live flu virus capable of causing the illness.

A runny nose, cough, vomiting, or diarrhoea is not typical of a simple injection-site reaction. Such symptoms may come from an infection or another cause that happened around the same time, so their severity and timing matter.

Rest if you feel tired and drink fluids regularly. A cool, clean cloth on the sore area can ease discomfort; avoid rubbing or pressing the injection site. Gentle movement of the arm may help it feel less stiff. If you need medicine for pain or fever, check with a pharmacist or clinician about a suitable choice, especially if you are pregnant, have a long-term condition, or take other medicines.

Keep watching how you feel rather than taking fever-reducing medicine in advance unless a clinician has advised it. If symptoms are worsening, interfering with normal activities, or not settling, contact a healthcare professional for individual advice.

Seek emergency help for trouble breathing, swelling of the face or throat, widespread hives, fainting, severe weakness, or sudden confusion after vaccination. These can be signs of a serious allergic reaction or another urgent problem.

Contact a clinician promptly if you develop a high or persistent fever, severe or unusual symptoms, or increasing redness, warmth, swelling, or pain at the injection site. Tell them when the vaccine was given and describe any other symptoms.

Ask which symptoms are expected for your vaccine, what you can take for discomfort, and whether your medical conditions or medicines change the advice. If you have had a previous reaction to a flu vaccine, ask whether you need an allergy assessment before another dose.