A guide for people with a weakened immune system

People who have a severely weakened immune system are being offered a third dose of coronavirus (COVID-19) vaccine. This is to help improve any protection you may have built from your first 2 doses.

What is coronavirus or COVID-19?

COVID-19 is a very infectious respiratory disease caused by the SARS-CoV-2 virus. It can be very serious in people who have a weakened immune system. There is no cure for COVID-19 although some newly tested treatments do help to reduce the risk of complications.

Why are you being offered a third dose of the COVID-19 vaccine?

This third dose is being offered to all those aged 12 years and older who had a weakened immune system around the time they had their first 2 doses of the COVID-19 vaccine. It is possible that you may not have responded as well as other people. This third dose may help to improve your immune response and give you better protection.

Your specialist can advise whether this applies to you. By having the third dose you may reduce your chance of catching the COVID-19 infection. And, if you do, the symptoms may be less severe and the illness shorter, than if you had not had the third vaccination.

People who need a third dose are those who had a severely weakened immune system around the time they had their first 2 doses.

This includes those who had or have:

  • blood cancers (such as leukaemia or lymphoma)
  • lowered immunity due to treatment (such as steroid medication, biological therapy, chemotherapy or radiotherapy)
  • lowered immunity due to inherited disorders of the immune system
  • an organ or bone marrow transplant
  • diseases that affect the immune system such as poorly controlled HIV
  • other diseases or treatments as advised by your specialist

How many doses will you need?

At this time you will need this 1 extra dose to help improve your protection. Like your previous doses, the vaccine will be given in your upper arm.

Timing of third dose

This should be given at least 8 weeks after your second dose but the timing will depend on any treatment you may be having. Your specialist will advise you on the best time to have your third dose.

Side effects

Very common side effects include:

  • having a painful, heavy feeling and
  • tenderness in the arm where you had your injection. This tends to be worst around 1 to 2 days after the vaccine
  • feeling tired
  • headache
  • general aches, or mild flu like symptoms

You can rest and take paracetamol (follow the dose advice in the packaging) to help make you feel better. Although feeling feverish is not uncommon for 2 to 3 days, a high temperature is unusual and may indicate you have COVID-19 or another infection.

Symptoms following vaccination normally last less than a week. If your symptoms seem to get worse or if you are concerned, you can call your GP or Practice Nurse.

How to get the vaccination

The COVID 111 Vaccination Team consult regularly with local Specialists to determine who is eligible to receive a third primary COVID-19 vaccination and the COVID 111 team will let you know when it is your turn to receive a COVID-19 third primary vaccine.

If you are receiving treatment with an off island specialist or think you are eligible for a third primary vaccination, please call the COVID 111 vaccination team who will refer you for a clinical review so that they can identify whether a third primary dose should be administered or if you actually require a booster COVID-19 vaccine.

People who shouldn’t have the third vaccination

If you’ve had a very severe reaction to the previous dose of the vaccine, you should discuss this with your doctor.

If you miss a vaccination

If you have not yet had either of your first 2 doses of the vaccine you should have them as soon as possible.

You will still need the third dose but the timing of it will depend on any treatment you may be having. Your specialist should be able to advise on the best timing.

Further information


Also view what to expect after vaccination or visit to download a copy of the information leaflet.

Updated 7 December 2021