Weak immune system and COVID-19 vaccines - additional dose

It is important that you are vaccinated against COVID-19 if you have a weak immune system (immunosuppressed or immunocompromised).

Having a weak immune system puts you at higher risk of serious illness if you get COVID-19. Getting vaccinated will give you some protection against this.

COVID-19 vaccines may be less effective for you than other people. Because your immune system may not respond as well to vaccination, you could still be at risk of becoming severely ill from COVID-19. You are also at risk of COVID-19 infection lasting for longer.

Additional dose

If you had a weak immune system at the time of your first round of COVID-19 vaccination, you should have been offered an additional dose to give you better protection.

When we say ‘first round of COVID-19 vaccination’ we mean your dose 1 and dose 2 if you got AstraZeneca, Moderna or Pfizer. Or your single dose if you got the Janssen vaccine.

You will still need a booster dose after your additional dose.

Booster dose

People aged 16 and over should get a booster dose at least 3 months after your additional dose.

An example of recommended COVID-19 vaccination for someone over 16 with a weak immune system is:

  • 2 doses of the Pfizer vaccine as your first round of COVID-19 vaccination
  • an additional Pfizer dose at least 2 months after this
  • a booster Pfizer dose at least 3 months after your additional dose

An additional dose followed by a booster will hopefully give you better protection against COVID-19. You may be offered a different vaccine depending on supply.

People who need an additional dose

People with the following conditions or treatments should get an additional dose:

Cancer patients

Cancer patients affected include:

  • all patients with advanced or metastatic cancers
  • haematological cancer - receiving treatment, pending treatment, or within 5 years of treatment

All cancer patients receiving (or within 6 weeks of receiving):

  • systemic cytotoxic chemotherapy
  • targeted therapy
  • monoclonal antibodies or immunotherapies
  • surgery or radical radiotherapy for lung or head and neck cancer
Kidney disease

People who have:

  • chronic kidney disease, on dialysis, or eGFR <30ml/min

People living with HIV not on treatment, or who have CD4 count <200x10-6L for adult


People who have:

  • been listed for solid organ or haematopoietic stem cell transplant (HSCT)
  • had a solid organ transplant at any time
  • had a HSCT within 12 months
Genetic diseases

People who have:

  • autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED)
  • inborn errors in the interferon pathway
Other conditions
  • immunedeficiency including ataxia telangiectasia
  • Brutun agammaglobulinaemia
  • chronic or cyclic neutropaenia
  • chronic granulomatous disease
  • complement deficiency
  • common variable immunedeficiency
  • other immunoglogulin deficiencies including isolated IgAand IgG subclass deficiency
  • Di George syndrome
  • Fanconi’s anaemia
  • severe combined immunedeficiency
  • Wiskott Aldrich Syndrome
  • Other immunedeficiency, meaning anyone considered immunocompromised by a consultant immunologist even if they do not fit into one of the categories specified on this page

People using any of the following for treatment in the last 6 months should have an additional dose:

  • Cyclophosphamide
  • Rituximab
  • Alemtuzumab
  • Cladribine
  • Ocrelizumab
High dose systemic steroids

The following doses of prednisolone (or equivalent dose of other glucocorticoid):

  • individuals over 10kg: ≥40mg/day for more than 1 week, or ≥20mg/day for 2 weeks or longer
  • children under 10kg: 2mg/kg/day for 2 weeks or longer
Other systemic medications potentially associated with immunocompromise

Immunomodulatory Treatments

Predominantly Antiproliferative agents

  • Azathioprine (Imuran®, Imuger®) (1-2 mgs/kg) 
  • 6-Mercaptopurine (Puri-Nethol®, Xaluprine®) (<1mg/kg) 
  • Mycophenolic acid (Cellcept®, Myclausen®, Mycolat®, Myfenax® 
  • Cyclophosphamide (Endoxana®) 
  • Leflunomide (Arava®, Repso®) 
  • Teriflunomide 

Calcineurin or T cell signalling inhibitors 

  • Tacrolimus (Advagraf®, Dailiport®, Envarsus® Modigraf®, Tacforius® 
  • Ciclosporin (Neoral®, Sandimmun®, Deximune®) 
  • Sirolimus (Rapamune®) 
  • Everolimus (Afinitor®, Certican®, Votubia®) 

Predominantly anti-inflammatory agents 

  • Methotrexate (Methofill®, Jylamvo®, Metoject®, Nordimet®) 
  • Apremilast (Otezia®) 
  • Dimethyl Fumarate (Skilarence®, Tecfidera®)

JAK inhibitors 

  • Tofacitinib (Xeljanz®) 
  • Baricitinib (Olumiant®) 
  • Ruxolitinib (Jakavi®) 

Agents for multiple sclerosis 

  • Fingolimod (Gilenya®) 
  • Dimethyl Fumarate (Skilarence®, Tecfidera®) 
  • Cladribine (Mavenclad®) 
  • Ocrelizumab (Ocrevus®) 
  • Natalizumab (Tysabri®) 
  • Alemtuzumab (Lemtrada®)

Other Biological agents 

TNF alpha inhibitors 

  • Adalimumab (Amgevita®, Amsparity®,Halimatoz®, Hefiya®, Hulio®, Humira®, Hyrimoz®, Idacio®, Imraldi®) 
  • Etanercept (Benepali®,Enbrel®, Erelzi®, Lifmior®) 
  • Infliximab (Flixabi®, Inflectra®, Remicade®, Remsima®, Zessly®) 
  • Golimumab (Simponi®) 
  • Certolizumab (Cimzia®)

Interleukin inhibitors 


  • Anakinra (Kineret®)
  • Canakinumab (Ilaris®)


  • Tocilizumab (RoActemra®)


  • Ustekinumab (Stelara®) 
  • Guselkumab (Termfya®) 
  • Tildrakizumab (Ilumetri®) 
  • Brodalumab (Kyntheum®) 
  • Ixekizumab (Taltz®) 
  • Secukinumab (Cosentyx®) 

Other mechanisms 

  • Abatacept (Orencia®)
  • Rituximab (Blitzima®, Mabthera®, Ritemvia®, Rixathon®, Riximyo®, Truxima® 
  • Eculizumab (Soliris®)

Talk to your doctor if you are not sure if you have a weak immune system.

When you should get an additional dose

You should get an additional dose at least 2 months after finishing a COVID-19 vaccine course.

If you had COVID-19 since you were vaccinated, you need to wait for 3 months before getting an additional dose.

How you will get your additional dose

Hospitals will identify the people who need an additional dose. You do not need to register or contact anyone. People who need an additional dose will receive a text message with an appointment for their vaccine.

These additional doses may be given through a HSE vaccination centre near you, or your hospital if you're an inpatient. GPs may also vaccinate some people.

Talk to your hospital team or GP if you have not had your additional dose yet and you need one because of a weak immune system.

Parents or legal guardians of 12 to 15 year olds will need to give consent for their child to get their COVID-19 vaccine.

Going to your vaccine appointment

Read about going to your vaccination appointment

Which vaccine you will get

Regardless of which COVID-19 vaccine course you had previously, if you are 30 years or older, you will be offered a single dose of either the:

If you are 29 years or younger, you will be offered a single dose of the Pfizer/BioNTech COVID-19 vaccine.

You should get this additional dose at least 2 months after you after you complete your first round of COVID-19 vaccination.

It is safe to get your COVID-19 vaccine at the same time as the flu vaccine or other vaccines you may need.

Safety of an additional dose

An additional dose of a COVID-19 vaccine has been:

Studies to date have not shown any concerns about serious side effects in people who have received an additional dose.

If you have any concerns about getting an additional dose, talk to your GP, or vaccinator. 

Staying safe from COVID-19

Continue to follow public health guidelines to protect yourself from COVID-19 after you have been vaccinated. Avoid situations where you could pick up the virus, such as crowded areas.

Everyone you live with who can get vaccinated should get a COVID-19 vaccine and booster dose when it is available to them. This will help to protect both you and them from COVID-19.

Read more about how COVID-19 affects people with a weak immune system, including information on steroids

Last updated: 14 January 2022 at 9.30am

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