Like all medicines, COVID-19 vaccines can cause side effects. Most of these are mild to moderate and short-term. Not everyone gets side effects.

If you are concerned about side effects, phone your GP for advice.

Serious side effects, like a severe allergic reaction, are extremely rare. Your vaccinator is trained to treat allergic reactions.

Fever after COVID-19 vaccines

It’s common to develop a fever (temperature of 38 degrees Celsius or above) after COVID-19 vaccination. This usually happens within 48 hours of getting a vaccine.

If you feel uncomfortable, take paracetamol or ibuprofen following the instructions on the box or leaflet.

If your fever starts more than 2 days after you are vaccinated, or lasts longer than 2 days, you should self-isolate (stay in your room).

Side effects of COVID-19 vaccines

The side effects for all the COVID-19 vaccines that have been used in Ireland are listed below.

Very common side effects

Very common side effects may affect more than 1 in 10 people.

These include:

  • tenderness or swelling in your arm where you had the vaccine
  • feeling tired
  • headache
  • muscle pain
  • joint pain
  • diarrhoea
  • fever (temperature of 38 degrees Celsius or above)
  • chills

Common side effects

Common side effects may affect up to 1 in 10 people.

These include:

  • nausea
  • vomiting
  • redness in your arm where you had the vaccine

Uncommon side effects

Uncommon side effects may affect up to 1 in 100 people.

These include:

  • itchiness where the vaccine was given
  • itchiness in general
  • a rash
  • swelling of the lymph glands – more often seen after the booster
  • sleeplessness
  • excessive sweating
  • night sweats
  • decreased appetite
  • lethargy, asthenia (lack of energy) and malaise (feeling unwell)
  • pain in the arm where you had the vaccine

Rare side effects

Rare side effects may affect up to 1 in 1,000 people.

These include:

  • an allergic reaction that can cause hives or swelling of the face
  • weakness in the muscles on one side of your face (that may cause it to droop temporarily)

Very rare side effects

Very rare side effects may affect up to 1 in 10,000 people.

These include:

  • myocarditis
  • pericarditis

Myocarditis and pericarditis are inflammatory heart conditions.

These conditions are more likely to occur after the second dose, and mostly happen within 14 days of getting the vaccine. The risk of these very rare conditions is higher in young men.

2 European studies have estimated the risk of myocarditis, after the second dose of the vaccine as:

  • 1 additional case for every 38,000 men aged 12 to 29 (within 7 days)
  • 1 additional case for every 17,500 men aged 16 to 24 (within 28 days)

We do not know the risk of myocarditis or other rare side effects after a booster dose yet.

Symptoms of myocarditis and pericarditis

Get urgent medical help if you get any of these symptoms in the weeks after the Pfizer/BioNTech vaccine:

  • breathlessness
  • palpitations (a forceful heartbeat that may be irregular)
  • chest pain

Extremely rare side effects

We do not know yet how many people are affected by extremely rare side effects. There is not enough data available at this time.

These include:

  • extensive swelling of the limb where you got your vaccine
  • tingling or prickling sensation, or loss of sensation in some part of the body
  • people who have had facial fillers may develop swelling of their face
  • a severe allergic reaction (anaphylaxis)
  • erythema multiforme – a skin reaction that causes red spots or patches on the skin. It may look like a target or ‘bulls-eye’ with a dark red centre surrounded by paler red ring

Very common side effects

Very common side effects may affect more than 1 in 10 people.

These include:

  • feeling tired
  • tenderness or swelling where you had the vaccine
  • headache
  • swollen lymph glands under the arm where you had the vaccine
  • muscle pain
  • joint pain
  • nausea or vomiting
  • fever (temperature of 38 degrees Celsius or above)
  • chills

Common side effects

Common side effects may affect up to 1 in 10 people.

These include:

  • diarrhoea
  • rash
  • rash, redness, or hives where you had the injection
  • reaction a few days after where you had the injection

Uncommon side effects

Uncommon side effects may affect up to 1 in 100 people.

These include:

  • itchiness where you had the vaccine injection
  • dizziness

Rare side effects

Rare side effects may affect up to 1 in 1,000 people.

These include:

  • Bell’s Palsy – a weakness in the muscles on one side of your face (that may cause it to droop temporarily)
  • swelling of your face – this can happen in people who have had facial fillers
  • reduced sense of touch or sensation in a part of the body

Very rare side effects

Very rare side effects may affect up to 1 in 10,000 people.

These include:

  • myocarditis
  • pericarditis

Myocarditis and pericarditis are inflammatory heart conditions.

The risk of these very rare conditions is higher in younger men.

These conditions are more likely to occur after the second dose and mostly happen within 14 days of getting the vaccine.

2 European studies have estimated the risk of myocarditis, after the second dose of the vaccine as:

  • 1 additional case for every 7,600 men aged 12 to 29 (within 7 days)
  • 1 additional case for every 5,320 men aged 16 to 24 (within 28 days)

We do not know the risk of myocarditis or other rare side effects after a booster dose yet.

Symptoms of myocarditis and pericarditis

Get urgent medical help if you get any of these symptoms in the weeks after the Moderna COVID-19 vaccine:

  • breathlessness
  • palpitations (a forceful heartbeat that may be irregular)
  • chest pain

Extremely rare side effects

We do not know yet how many people are affected by extremely rare side effects. There is not enough data available at this time.

These include:

  • erythema multiforme – a skin reaction that causes red spots or patches on the skin. It may look like a target or ‘bulls-eye’ with a dark red centre surrounded by paler red ring
  • hypersensitivity reactions (unwanted increased response from the immune system)
  • severe allergic reaction (anaphylaxis)
  • flare-ups of capillary leak syndrome

Symptoms of capillary leak syndrome

Capillary leak syndrome causes fluid to leak from small blood vessels. There is a possible risk of flare-ups in people with a history of capillary leak syndrome. Even though the risk of the condition is extremely low, you should know the signs to watch for.

Get urgent medical help if you get any of these symptoms after the Moderna vaccine:

  • rapid swelling of the limbs (arms and legs)
  • sudden weight gain

You may also feel faint due to low blood pressure.

People usually reported capillary leak syndrome within the first few days of getting this vaccine. Watch out for these symptoms in the days after your vaccination.

The Novavax COVID-19 vaccine is called Nuvaxovid.

Very common side effects

Very common side effects may affect more than 1 in 10 people.

These include:

  • feeling tired
  • feeling generally unwell
  • headache
  • nausea or vomiting
  • muscle pain
  • joint pain
  • tenderness or pain in your arm where you had the vaccine injection

Common side effects

Common side effects may affect up to 1 in 10 people.

These include:

  • fever (temperature of 38 degrees Celsius or above)
  • chills
  • pain in extremities (arm, hand, leg or foot)
  • redness or swelling where the vaccine was given

Uncommon side effects

Uncommon side effects may affect up to 1 in 100 people.

These include:

  • swelling of the lymph glands
  • high blood pressure lasting for a few days after vaccination
  • a rash
  • redness of the skin
  • general itchiness
  • itchiness where the vaccine was given
  • hives

Some side effects are seen more often after the second dose.

Novavax vaccine is new

This COVID-19 vaccine has gone through the same clinical trials and safety checks as all other licensed vaccines. But the vaccine is new and long-term side effect information is limited.

As more people in Ireland and around the world get this vaccine, more information on side effects may become available. We will update this page with any new side effects information.

Very common side effects

Very common side effects may affect more than 1 in 10 people.

These include:

  • feeling tired
  • pain in the arm where you had the vaccine injection
  • headache
  • muscle pain
  • nausea

Common side effects

Common side effects may affect up to 1 in 10 people.

These include:

  • redness or swelling where you had the injection
  • joint pain
  • cough
  • fever (temperature of 38 degrees Celsius or above)
  • chills

Uncommon side effects

Uncommon side effects may affect up to 1 in 100 people.

These include:

  • feeling weak or generally unwell
  • back pain
  • dizziness
  • muscle weakness
  • pain in the limbs
  • pain in the throat
  • a rash
  • sneezing
  • excessive sweating
  • a tremor
  • diarrhoea
  • an unusual feeling in the skin, such as tingling or a crawling feeling (paraesthesia)

Rare side effects

Rare side effects may affect up to 1 in 1,000 people.

  • allergic reaction or hives
  • decreased feeling or sensitivity, especially in the skin (hypoesthesia)
  • swollen lymph glands
  • vomiting
  • ringing in the ears (tinnitus)
  • blood clots in the deep veins – such as deep vein thrombosis and pulmonary embolisms

Blood clots in deep veins are more likely in people who have pre-existing risk factors for these conditions.

Very rare side effects

Very rare side effects may affect up to 1 in 10,000 people.

These include:

  • very unusual blood clots with low platelets
  • Guillain-Barré syndrome (GBS)

Very unusual blood clots with low platelets

Very rarely, 1 in 300,000 people may develop very unusual blood clots with low platelets. 1 in 10 of these people may die. The risk of this very rare condition is higher in younger people.

Talk to your GP, doctor or the person giving you your vaccination about the risks and benefits of getting this vaccine.

Most people who got this very rare side effect got it within 14 days of getting the Janssen vaccine.

Symptoms of very rare blood clots

Get urgent medical help and mention your recent vaccination if you:

  • are breathless
  • have pain in the chest or stomach
  • have swelling or coldness in a leg
  • get a severe or worsening headache (particularly 3 or more days after the vaccine)
  • have blurred vision
  • feel confused
  • have seizures
  • have persistent bleeding under the skin where there was no previous injury
  • have many small bruises, reddish or purplish spots, or blood blisters under the skin

Guillain-Barré syndrome (GBS)

GBS is a rare and serious condition that affects the nerves. Symptoms can range from mild weakness to severe paralysis (being unable to move a part of your body). Most people eventually fully recover even from the most severe symptoms. Some may continue to experience weakness.

Getting GBS after having the Janssen vaccine is very rare. Only a small number of people have reported getting the condition after being vaccinated.

You should know the symptoms to look out for in the weeks after being vaccinated.

Get urgent medical help if you develop:

  • double vision or difficulty moving your eyes
  • difficulty swallowing, speaking, or chewing
  • co-ordination problems and unsteadiness
  • difficulty walking
  • tingling sensations in your hands and feet
  • weakness in your arms, legs, chest or face
  • problems with bladder control and bowel movements

Extremely rare side effects

We do not know yet how many people are affected by extremely rare side effects. There is not enough data available at this time.

These include:

  • severe allergic reaction (anaphylaxis)
  • capillary leak syndrome
  • immune thrombocytopenia
  • transverse myelitis (inflammation of the spinal cord)
  • cutaneous small vessel vasculitis (inflammation of blood vessels in the skin)

Capillary leak syndrome

A very small number of people have experienced capillary leak syndrome after getting the Janssen vaccine.

Capillary leak syndrome is a very rare but serious condition. It can sometimes be fatal. Do not get the Janssen vaccine if you have previously had capillary leak syndrome.

Get urgent medical attention if you have had a Janssen vaccine in the past few days and you notice:

  • rapid swelling of your arms or legs
  • sudden weight gain

You may also feel faint due to low blood pressure.

Capillary leak syndrome is usually reported within 4 days of getting the Janssen vaccine. Watch out for these symptoms in the days after your vaccination.

Immune thrombocytopenia

Extremely rarely, very low levels of blood platelets (immune thrombocytopenia) may happen. This can cause bleeding and can sometimes be fatal. It usually happens within 4 weeks of getting the Janssen vaccine. Some cases have been seen in people who have previously had immune thrombocytopenia.

Cutaneous small vessel vasculitis

A very small number of cases of cutaneous small vessel vasculitis (inflammation of blood vessels in the skin) have occurred in people after this vaccine. In most cases, symptoms get better with supportive care.

The official name of AstraZeneca’s COVID-19 vaccine is ‘Vaxzevria’. But most people call it ‘AstraZeneca’.

This vaccine is not available in Ireland at this time.

Very common side effects

Very common side effects may affect more than 1 in 10 people.

These include:

  • feeling tired
  • feeling unwell
  • tenderness, bruising, pain, warmth or itching in the arm where you had the vaccine injection
  • headache
  • muscle pain
  • joint pain
  • nausea
  • feeling feverish or having chills

Common side effects

Common side effects may affect up to 1 in 10 people.

These include:

  • redness or swelling where you had the injection
  • diarrhoea
  • vomiting
  • fever (temperature of 38 degrees Celsius or above)
  • pain in hands and feet
  • flu-like illness
  • lack of energy
  • a low platelet count – this is a mild, temporary decrease in blood platelets that can be picked up on blood tests but does not cause any symptoms

Uncommon side effects

Uncommon side effects may affect up to 1 in 100 people.

These include:

  • reduced appetite
  • dizziness
  • sleepiness
  • excessive sweating
  • swollen lymph glands
  • rash
  • lethargy (lack of energy)
  • itchy skin or hives
  • abdominal (tummy) pain
  • muscle spasms

Rare side effects

Rare side effects may affect up to 1 in 1,000 people.

This includes:

  • one-sided facial drooping

Very rare side effects

Very rare side effects may affect up to 1 in 10,000 people.

These include:

  • very unusual blood clots with low platelets
  • Guillain-Barré syndrome

Extremely rare side effects

We do not know yet how many people are affected by extremely rare side effects. There is not enough data available at this time.

These include:

  • severe allergic reaction (anaphylaxis)
  • hypersensitivity
  • an allergic reaction that can cause your face to swell
  • capillary leak syndrome
  • immune thrombocytopenia – some cases have been seen in people who have previously had immune thrombocytopenia
  • unusual blood clots in the brain, not associated with low level of blood platelets
  • transverse myelitis (inflammation of the spinal cord)
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If you get COVID-19 symptoms after your vaccine

COVID-19 vaccines cannot give you COVID-19.

It’s possible to get COVID-19 before getting your vaccine and not realise you have the symptoms until after your vaccination.

If you have any symptoms of COVID-19, self-isolate (stay in your room).

Reporting side effects of COVID-19 vaccines

As with all vaccines, you can report suspected side effects to the Health Products Regulatory Authority (HPRA).

You can report a COVID-19 vaccine through the HPRA’s online adverse reaction report form

Give as much information as possible. Include the vaccine batch number if you have it. You’ll find this on your vaccine record card. You can also ask your doctor or a family member to report side effects for you.

The HPRA cannot provide clinical advice on individual cases. Talk to your doctor or pharmacist about any medical concerns you may have.

Read more about reporting vaccine side effects to the HPRA

Safety of COVID-19 vaccines

All vaccines are tested to make sure they are safe and work before they can be used. The HSE only uses a vaccine if it meets the required standards of safety and effectiveness.

Most people can have any of the COVID-19 vaccines, but some people are only offered certain vaccines. For example, the Moderna vaccine is only used in adults aged 30 and older.

You will be offered the vaccine that is most suitable for you.

Most people can safely get the Pfizer/BioNTech COVID-19 vaccine.

But this vaccine is not recommended if you:

  • have had a severe allergic reaction to any of the ingredients in this vaccine – including polyethylene glycol or PEG
  • have been told by a doctor that you should not get this vaccine or the Moderna vaccine – they are both mRNA vaccines
  • have had a severe allergic reaction to a previous dose of this vaccine or the Moderna vaccine
  • had myocarditis after a previous dose of this vaccine or the Moderna vaccine

Talk to your doctor before getting this vaccine if you:

  • have had a severe allergic reaction (anaphylaxis) in the past, including to any other vaccine or medication
  • had pericarditis after a previous dose of this vaccine or the Moderna vaccine

Ingredients of Pfizer/BioNTech COVID-19 vaccine

The Pfizer/BioNTech COVID-19 vaccine does not contain eggs, preservatives or latex.

For a full list of ingredients, read the patient information leaflet for the Pfizer/BioNTech COVID-19 vaccine (Comirnaty).

The Moderna (Spikevax) COVID-19 vaccine is only used in adults aged 30 and over in Ireland.

If you are under 30 and had the Moderna vaccine, you should get the Pfizer/BioNTech vaccine for any other doses you need.

Moderna is not recommended if you have had a severe allergic reaction to:

  • any of the ingredients in this vaccine – including polyethylene glycol or PEG
  • Trometamol – an ingredient in contrast dyes used for MRI scans

You should also not get this vaccine if you:

  • have been told by a doctor that you should not get this vaccine or the Pfizer/BioNTech COVID-19 vaccine – they are both mRNA vaccines
  • had myocarditis after a previous dose of this vaccine or the Pfizer/BioNTech COVID-19 vaccine

Talk to your doctor before getting this vaccine if you:

  • have had a severe allergic reaction (anaphylaxis) in the past, including to any other vaccine or medication
  • had pericarditis after a previous dose of this vaccine or the Pfizer/BioNtech COVID-19 vaccine
  • have a history of capillary leak syndrome

Ingredients of Moderna COVID-19 vaccine

The Moderna COVID-19 vaccine does not contain eggs, preservatives or latex.

For a full list of ingredients, read the patient information leaflet for the COVID-19 Moderna vaccine.

Who should not get the Janssen COVID-19 vaccine

You may be offered the Janssen vaccine if it is not safe for you to get the Pfizer vaccine or the Moderna vaccine.

The Janssen vaccine is not recommended for those under the age of 50. This is because of the very rare risk of unusual blood clots with low platelets in people under 50 who get the Janssen vaccine.

You should not get the Janssen COVID-19 vaccine if you:

  • had a severe allergic reaction to any of the ingredients in the vaccine. This includes polysorbate 80. Read the European Medicines Agency’s Janssen COVID-19 vaccine information to see the list of ingredients
  • had a severe allergic reaction to a previous dose of this vaccine or the AstraZeneca vaccine – this is because the Janssen and AstraZeneca vaccines are both viral vector vaccines
  • have been told by a doctor that you should not have this vaccine or the AstraZeneca vaccine for medical reasons
  • had blood clots with low platelets after a previous dose of the AstraZeneca vaccine
  • have a history of capillary leak syndrome

Talk to your GP about the risks and benefits of getting this vaccine if:

  • you have had a severe allergic reaction (anaphylaxis) in the past, including to any other vaccine or medication
  • you have had thrombocytopenia in the past

You will need your platelet levels monitored after this vaccine if you have a history of immune thrombocytopenia.

If you are pregnant

If you are pregnant, you will be offered either the Pfizer/BioNTech vaccine or the Moderna vaccine. You will only be offered the Moderna COVID-19 vaccine if you are aged 30 or over.

Read more about COVID-19 vaccines in pregnancy

Ingredients of the Janssen COVID-19 vaccine

The Janssen COVID-19 vaccine does not contain eggs, preservatives or latex.

For more information, read the European Medicines Agency’s Janssen COVID-19 vaccine page.

Most people aged 18 or older can safely get the Novavax COVID-19 vaccine Nuvaxovid.

But this vaccine is not recommended if you have had:

The Janssen and AstraZeneca COVID-19 vaccines also contain Polysorbate 80.

Talk to your doctor before getting a COVID-19 vaccine if you:

  • have had a severe allergic reaction (anaphylaxis) in the past, including to any other vaccine or medication