Like all medicines, vaccines can cause side effects. These are usually mild and only last a few days, and not everyone gets them. Even if you do have symptoms after the first dose, you still need to have the second dose.
Very common side effects include:
• having a painful, heavy feeling and tenderness in the arm where you had your injection for several days after the vaccine
• feeling tired
• headache
• general aches, or mild flu like symptoms
Although a mild fever is not uncommon for two to three days, a high temperature is unusual and may indicate you have COVID-19 or another infection. You can take the normal dose of paracetamol (follow the advice in the packaging) and rest to help you feel better. Do not exceed the normal dose.
An uncommon side effect is swelling of the local glands. These symptoms normally last less than a week. If your symptoms seem to get worse or if you are concerned, look at 111.wales.nhs.uk online, and if necessary call NHS 111 Wales or your GP surgery. If 111 is not available in your area, please call 0845 46 47. Calls to NHS 111 Wales are free, calls to 0845 46 47 cost 2p per minute (plus your telephone provider’s usual charge).
If you do seek advice from a doctor or nurse, make sure you tell them about your vaccination (show them your vaccination card if possible) so that they can assess you properly. You can also report suspected side effects to vaccines and medicines through the Yellow Card scheme.
Rarely, some people have an allergic reaction soon after a vaccination. This may be a rash or itching affecting part or all of the body. Even more rarely, some people can have a severe reaction soon after vaccination, which causes breathing difficulties and may cause them to collapse.
This is called anaphylaxis and can happen with other medicines and food. These reactions are rare and nurses are trained to manage them. People who have an anaphylactic reaction can be successfully treated and usually recover within a few hours.