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.

You should have already received one of the below COVID-19 vaccine courses:

  • 2 doses of Pfizer/BioNTech - ‘Comirnaty’
  • 2 doses of AstraZeneca - 'Vaxzevria'
  • 2 doses of Moderna - 'Spikevax'
  • 1 dose of Johnson & Johnson - 'Janssen'

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 for those with a weak immune system

If you had a weak immune system at the time of your initial course of COVID-19 vaccination, you may be offered another COVID-19 vaccine dose to give you better protection.

For example, if you already had 2 doses of the Pfizer vaccine, you will be offered a third dose at least 2 months later. This will hopefully give you better protection against COVID-19.

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.

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 HSE vaccination centre near you, or your hospital if you're an inpatient. GPs may also vaccinate some people.

You will need an appointment for your additional dose. You cannot get an additional dose at a walk-in vaccination clinic.

Going to your vaccine appointment

Read about:

Which vaccine you will get

Regardless of which COVID-19 vaccine course you had previously, you will be offered a single dose of either the:

You should get this additional dose at least 2 months after you are fully vaccinated. 

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 aged 12 and older should get vaccinated against COVID-19. 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: 20 October 2021 at 11.45am

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