What should you know about an inactivated flu shot?

An inactivated flu shot trains your immune system with treated influenza material and cannot cause influenza infection. It is given by injection, commonly into an upper-arm muscle, and is designed to help your body recognise influenza viruses if you encounter them later.

Inactivated means the viral material has been treated so it cannot multiply in the body. The vaccine can still show the immune system features it needs to recognise. A sore arm, tiredness, or a mild fever can occur as the immune system responds; these effects are different from having influenza. Protection is not immediate, so vaccination is best discussed before influenza is circulating widely.

Tell the vaccinator about a previous serious reaction to a flu vaccine or any severe allergy, and mention if you are unwell or have a condition or treatment that affects immunity. Wear clothing that leaves the upper arm accessible. After the injection, remain for the observation period recommended by the clinic. Rest, drink fluids, and use a cool compress for local soreness if helpful. Follow the product and clinician advice before taking medicine for discomfort.

Seek urgent help for trouble breathing, swelling of the face or throat, widespread hives, collapse, or severe dizziness after vaccination. Contact a clinician if the injection-site reaction is worsening, pain is severe, or fever or illness is persistent. These symptoms need assessment because they may have another cause or require treatment.

Ask which inactivated formulation is suitable for your age and health, whether another vaccine should be spaced from it, and what to do if you have had a previous reaction. You can also ask when protection is expected and whether your current symptoms should delay vaccination.