Safety - AstraZeneca COVID-19 vaccine

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.

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

Who should not get the AstraZeneca COVID-19 vaccine

Most people will be able to safely get the AstraZeneca COVID-19 vaccine.

But you should not get the AstraZeneca COVID-19 vaccine if you:

  • have had a severe allergic reaction to a previous dose of this vaccine
  • have been told by a doctor not to get the Janssen vaccine for medical reasons - this is because the AstraZeneca and Janssen vaccines are both viral vector vaccines
  • have had a severe allergic reaction to any of the ingredients in the vaccine, including polysorbate 80. Read the manufacturer’s patient information leaflet on the EMA website
  • had an unusual blood clot with low blood platelets after your first dose of AstraZeneca
  • have previously had 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 have not been given a vaccine yet, you will be offered a different COVID-19 vaccine to the AstraZeneca vaccine.

If you have already had your first dose of the AstraZeneca vaccine, you should still get your second dose.

Being fully vaccinated will reduce the chance of you becoming very unwell.

Read more about COVID-19 vaccines in pregnancy

Very rare side effects

Very rare side effects of the AstraZeneca vaccine include:

  • very unusual blood clots
  • capillary leak syndrome

Very unusual blood clots

Very rarely, people may develop very unusual blood clots with low platelets after getting the AstraZeneca vaccine.

The European Medicines Agency has approved this vaccine for use in those aged 18 and over with the overall benefits outweighing the risks.

Though the risk of developing blood clots with low platelets is very low, it is slightly higher in those under 50 years of age.

It is seen in approximately:

  • 1 in 100,000 people aged 50 and over
  • 1 in 50,000 people aged 18 to 49

These blood clots are less likely to be reported after the second dose of the vaccine.

Capillary leak syndrome

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

Capillary leak syndrome can cause rapid swelling of your arms and legs and sudden weight gain. Along with this, your blood pressure may also drop suddenly.

It is a rare but serious condition. It can sometimes be fatal.

If you are on blood-thinning treatment or at risk of a blood clot

You can still get the AstraZeneca COVID-19 vaccine if you:

  • recently had a blood clot (not vaccine-related)
  • are on blood-thinning treatment
  • have a condition that makes you more likely to get a blood clot
  • have a family history of blood clots

There is no reason to delay vaccination if you are offered this vaccine. The blood clots associated with these very rare side effects after getting the vaccine are unusual blood clots with low platelets.

Like everyone who gets the vaccine, you should know the very rare side effects to look out for.

If you are worried, talk to your GP.

Viral vector vaccine

The AstraZeneca COVID-19 vaccine is a viral vector vaccine.

Work to develop COVID-19 vaccines moved much faster than usual to make them available as soon as possible.

Read about COVID-19 vaccine development

Ingredients of the AstraZeneca COVID-19 vaccine

The AstraZeneca 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 AstraZeneca vaccine.


This content was fact checked by vaccine experts working in Ireland.

Last updated: 19 October 2021 at 2.20pm

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