People who received a first dose of AstraZeneca can now receive an mRNA (Pfizer/Moderna) vaccine as their second dose

HSE Press Statement: 02 September 2021

People who received a first dose of AstraZeneca can now receive an mRNA (Pfizer/Moderna) vaccine as their second dose

  • NIAC recommends that receiving two doses of the same vaccine are preferred for all age groups, where possible.
  • Dose 2 walk-in vaccination clinics for people who wish to get an mRNA vaccine after their first dose of the AstraZeneca vaccine

From today (02 September 2021) people who have received a first dose of Vaxzevria (AstraZeneca), can now choose to receive an mRNA (Pfizer/Moderna) vaccine as their second dose.

Dr Lucy Jessop, Director of Public Health, HSE National Immunisation Office explains:

“AstraZeneca is a 2-dose vaccine and you need a second dose to be fully vaccinated. If you had your first dose of the AstraZeneca vaccine, you should get a second dose of the same vaccine.

Millions of people have been given 2 doses of the AstraZeneca vaccine. There is extensive research about the safety and effectiveness of 2 doses of this vaccine.”

“However, for the small number of people who have not had a second dose of AstraZeneca, they now have the option to receive an mRNA COVID-19 vaccine dose instead if it is suitable for them, which will mean they are fully vaccinated. The HSE advice is that it’s safer to receive a second dose and become fully vaccinated, than to remain only partially vaccinated.”

Where to get an mRNA Dose 2

People who wish to get an mRNA vaccine after their first dose of the AstraZeneca vaccine, can attend an mRNA dose 2 walk-in vaccination clinic. Most dose 2 walk-in clinics will be offering Pfizer.

People can go to any mRNA dose 2 walk-in clinic location as long as their vaccination is due and they have proof of their first dose (e.g. their vaccination record card). It does not matter where the first dose was given (for example, through a GP, pharmacy, healthcare setting or in another country)

The dose 2 mRNA vaccine should be given at least 28 days after getting the first dose of AstraZeneca. People are fully vaccinated:

  • 7 days after their Pfizer/BioNTech dose
  • 14 days after their Moderna dose

Two doses of an AstraZeneca or an mRNA COVID-19 vaccine are needed for best possible protection against COVID-19.

Attending a Vaccination Centre

Find a walk-in vaccination centre

Timings in the designated vaccination centres will vary across locations. For more information on going to a walk-in vaccination clinic, see the HSE website.


Issued by the HSE National Press Office

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Notes to editor:

Efficacy and safety of mixing vaccines

Studies have been done to check how a person’s immune system responds to getting a second dose of an mRNA vaccine after a first dose of AstraZeneca. The studies have shown that a person may have a stronger immune system response when compared to getting two doses of AstraZeneca.

The strong immune response means that this combination of vaccines is expected to protect against COVID-19 disease but this has not yet been proven. It has also not yet been shown that this response gives you more protection against COVID-19 than two doses of AstraZeneca.

People can choose this option because it has been advised by NIAC in Ireland. It is not yet approved and licensed by the EMA. At the moment, the EMA has approved the use of two doses of the same vaccine only. Visit for more information.

We have less information about the safety of mixing two different COVID-19 vaccines compared with having two doses of the same vaccine. So far, there have not been concerns about serious side effects with this option.

Studies say that some side effects are more common than when two doses of the same vaccine are used. These include pain where the injection was given, headache, muscle aches, tiredness, chills and fever.

Read the information about mRNA vaccines, including side effects of the vaccine.

Last updated on: 02 / 09 / 2021