The most common side effect of the flu vaccine is soreness at the injection site. Some people do also find that they have symptoms resembling the common cold, such as a headache, runny nose, cough, or sore throat. These usually pass in a few days.
In very rare cases, vaccination can lead to anaphylaxis (a severe allergic reaction). However this tends to happen very quickly after injection. All LloydsPharmacy pharmacists administering the vaccine are trained in the emergency treatment of anaphylaxis.