FAQs 6 months - 4 years

The following questions and answers have been developed by the National Immunisation Office. 

Which COVID-19 vaccine is approved for children aged 6 months to 4 years?

The only COVID-19 vaccine which has been approved in Ireland for use in children aged 6 months to 4 years is Comirnaty® 3 micrograms (0.2ml).

Spikevax 25 micrograms (0.25ml) has been licensed in other countries for children aged 6 months to 5 years but it is not being marketed in Ireland.

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Why is the COVID-19 vaccine being made available for children aged 6 months to 4 years?

A primary course of COVID-19 vaccination is recommended for those aged 6 months to 4 years with underlying conditions that place them at higher risk of severe COVID-19. The presence of an underlying condition (as listed in the table below) significantly increase the risk of hospitalisation and severe disease.

However, COVID-19 vaccination is being offered to all children aged 6 months to 4 years because of:

  • the protection provided against severe COVID-19 infection and Multisystem Inflammatory Syndrome in Children (MIS-C, further details below) and their late consequences
  • the enhanced protection vaccination gives to those who have had COVID-19 infection
  • the modest protection for immunocompromised and other household contacts who are too young to be vaccinated
  • the safety profile of the vaccines
  • similar vaccine immunogenicity to that in older children and adolescents.

Multisystem Inflammatory Syndrome in Children (MIS-C) is a rare but serious hyperinflammatory syndrome related to prior SARS-CoV-2 infection, in which different organs can become inflamed. The incidence of MIS-C is about 100/100,000 in those under 21 years of age, with a median age of 9 years old, and 75% of cases with no underlying medical condition. Most children recover with appropriate treatment.

See NIAC Immunisation Guidelines for Ireland Table 5a.2 for conditions or treatments associated with very high or high risk of severe COVID-19 disease.



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What is the dose of Comirnaty® for children aged 6 months to 4 years?

The dose of Comirnaty® for children aged 6 months to 4 years is 3 micrograms (0.2ml). The primary course for all children in this age group (including children with immune compromise) is three doses.

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What is the recommended interval between doses?

The primary course consists of three doses with an interval of three weeks between dose one and two, and an interval of eight weeks between dose two and three.

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What should I do if the interval between doses is longer than recommended?

If the interval between doses is longer than the recommended interval, the next dose should be given as soon as possible. The course does not need to be restarted.

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What should I do if the interval between doses is shorter than recommended?

If the second dose is given more than four days before the minimum interval this is not considered a valid dose. A further dose should be given at least eight weeks after the invalid dose.

If the third dose is given more than four days before the minimum interval this is not a valid dose. A minimum interval of 21 days may be used if there is urgency to achieve protection. A further dose should be given at least eight weeks after the invalid dose.

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How should the vaccine be stored?

The vaccine is supplied to sites/clinics by the HSE NCCS at +2°C to +8°C with a shelf life of up to 10 weeks. Vials should be stored in pharmaceutical fridge between +2°C to +8°C. The new “use before “date and time is on the “HSE Scan me label” which has been affixed by NCCS once vials are removed from ULT freezer. Do not refreeze vials.

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What volume of 0.9% saline should be used to dilute a vaccine vial?

The vaccine must be diluted with 2.2ml of 0.9% sodium chloride. Gently invert the vaccine vial 10 times prior to use. Do not shake the vial.

After dilution, the vaccine must be kept at +2°C to +30°C and used within 12 hours, after which the vial must be discarded.

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How many doses of 0.2mls are in a diluted vial of the vaccine?

After dilution, there are 10 doses of 0.2ml in a vial of the vaccine. If 11 or 12 doses of 0.2ml can be safely and accurately withdrawn from a diluted vial, they can be used as valid doses. There should not be any more than 12 doses of 0.2ml when the vial has been diluted properly. There should be no pooling of the contents of different vials.

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Where should the vaccine be injected?

The vaccine must be delivered intramuscularly (IM injection). For infants aged 6 months to 11 months, the recommended injection site is the anterolateral aspect of the thigh. For children aged 1 year to 4 years of age, either the deltoid muscle or the anterolateral aspect of the thigh can be used (depending on muscle mass) as the injection site.

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What technique should be used for those with bleeding disorders or on anticoagulants?

Individuals with a bleeding disorder or receiving anticoagulant therapy may develop haematomas in IM injection sites. Prior to vaccination, inform the parent/guardian about this risk. For those with thrombocytopoenia (platelet count <50 x109L), consult the supervising consultant. Those with inherited coagulopathies receiving factor replacement therapy should receive it on the day of vaccination, prior to IM vaccination. If there is uncertainty about the need for replacement therapy, contact the child’s supervising consultant.

Those receiving long-term anticoagulation with either warfarin or heparin are not considered to be at higher risk of bleeding complications following immunisation. There is no reason to expect that there is a greater risk of bleeding complications with the newer types of anticoagulants and antiplatelet agents, than with other anticoagulants.

Technique for IM injections in persons with bleeding disorders or on anticoagulants:

  • Only one injection per muscle mass should be given at each visit. Use a 23 or 25 gauge needle to reduce the pressure gradient and cause less trauma to the tissue. The vaccine should be injected slowly (≥5 seconds) to reduce the risk of tissue damage.
  • Firm pressure should be applied to the site for 5 to 10 minutes after injection.
  • Stabilisation of the limb will reduce the risk of a haematoma.
  • The site should not be rubbed or massaged.
  • Instruct the parent/guardian to monitor the injected limb and to report any concerns to their supervising consultant.

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Can other vaccines be co-administered with the COVID-19 vaccine in children aged 6 months to 4 years?

No, in this age group there must be at least a 2 week interval between the administration of the COVID-19 vaccine and any other vaccines. No interaction studies in young children have been performed on coadministration of Comirnaty® with childhood vaccines. Priority should be given to other routine childhood immunisations. Until there is more evidence it is prudent to separate COVID-19 vaccination in children aged 6 months-4 years from other vaccines for a period of 14 days.

As a precaution, if your child has recently received the monkeypox vaccine (Imvanex or Jynneos), they need to wait 4 weeks before they get their COVID-19 vaccine because of the unknown risk of myocarditis.

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What are the recommended observation periods following administration of Comirnaty® 3 micrograms (0.2ml)?

Vaccine recipients: 15 minutes

Those with a history of mastocytosis: 30 minutes

Those with immediate itching, swelling or urticarial reaction at the vaccination site: 30 minutes or longer as clinically indicated.

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What is the vaccine efficacy? 

In a study 1,254 children aged 6 months-4 years who were SARS-CoV-2 negative at baseline received three doses of either Comirnaty® (n=873) or placebo (n=381). The median follow-up period following dose three was 1.3 months. An estimated vaccine efficacy (VE) against SARS-CoV-2 infection of 73% was observed. A total of 21 cases of SARS-CoV-2 were reported in the placebo group and 13 cases in the vaccinated group.

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What is the duration of immunity following vaccination?

There is insufficient information to determine the duration of protection from the vaccine. Vaccine recipients may not have optimal protection until seven days after the third dose, and the vaccine may not protect all vaccinees. Vaccinated children should continue to follow current public health guidance to protect themselves and others.

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What are the most common adverse reactions seen in children aged 6 months to 4 years following the primary course of COVID-19 vaccination?

The most frequent adverse reactions in those that received any primary course dose included:

in infants 6-23 months of age, irritability (> 60%), drowsiness (> 40%), decreased appetite (>30%), tenderness at the injection site (> 20%), injection site redness and fever (> 10%)

in children 2-4 years of age, pain at injection site and fatigue (> 40%), injection site redness and fever (> 10%).

A higher rate of pyrexia was seen after administration of the second dose.

This medicinal product is subject to additional monitoring. This will allow quick identification of new safety information. Healthcare professionals are asked to report any suspected adverse reactions to the HPRA.

In the US, over one million children aged 6 months-5 years have received at least one dose of either Comirnaty® or Spikevax®. The CDC reviewed adverse events and the most commonly reported symptoms were irritability or crying, sleepiness, loss of appetite and fever. Almost all (98%) reports were for non-serious events. Of the serious events reported, two were likely attributable to the vaccination, one febrile convulsion and one anaphylaxis associated with a dosing error. No cases of myocarditis were reported.

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When is an additional dose or booster dose recommended for children aged 6 months to 4 years?

There are currently no indications for additional doses or booster doses for this age group. The primary course of 3 doses of Comirnaty® 3 micrograms (0.2ml) is the only recommendation for COVID-19 vaccination for children aged 6 months to 4 years.

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What are the contraindications and precautions with this vaccine?


Anaphylaxis following a previous dose of the vaccine or any of its constituents (including polyethylene glycol (PEG) and trometamol).

Appropriate support should be available in case of anaphylaxis or fainting after vaccine administration. Precautions should be in place to minimise injury from fainting. 


Acute severe illness; defer until recovery.

Previous history of myocarditis or pericarditis after any COVID-19 vaccine - seek specialist advice.

Vaccination should be postponed in children with a previous history of MIS-C, until clinical recovery or until 90 days or more since diagnosis, whichever is the longer.

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What are the considerations for a child planned to begin immunosuppressing therapy?

Children with planned immunosuppressing therapy should ideally complete vaccination two weeks before treatment. The recommended minimum interval may be used. Specialists should consider the child’s risk and likelihood of disease exposure, and provide advice based on knowledge and understanding of their immune status and likely immune response to vaccination.

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What are the considerations for a child who is immunocompromised?

If the child is already immunocompromised (either due to disease or treatment), they may be vaccinated if they have no contraindications. Vaccine efficacy may be lower in immunocompromised individuals.

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Which Comirnaty® vaccine dose should a child receive if they are currently 4 years of age, but will turn 5 years old before they can receive a second dose?

The dose of Comirnaty® depends on the age at the time of the vaccination e.g., a 4 year old child should receive the first dose of Comirnaty® 3 micrograms (0.2ml) and if they have turned 5 years of age at the time of a subsequent dose, the dose given should be Comirnaty® Original/Omicron BA.4-5 10 micrograms (0.2ml) for those aged 5-11 years.

Therefore, if a child becomes five years of age before completion of the recommended course, the schedule should be completed with the age appropriate dose, Comirnaty®Original/Omicron BA.4-5 10 micrograms (0.2ml) for those aged 5-11 years, as follows:

If they have received one dose of Comirnaty® 3 micrograms: leave an interval of three weeks, then give two doses of Comirnaty®Original/Omicron BA.4-5 10 micrograms (0.2ml) eight weeks apart.

If they have received two doses of Comirnaty®3 micrograms: leave an interval of eight weeks, then give one dose of Comirnaty®Original/Omicron BA.4-5 10 micrograms (0.2ml).

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What if only the diluent of Comirnaty® is administered?

The diluent for Comirnaty® (Pfizer BioNTech) is sodium chloride, which is salt and purified water so no adverse reactions would be expected.

The error should be explained to the parent/guardian and a correctly diluted dose of the vaccine should be given to the child as soon as possible. This should be reported to HPRA if this is associated with an adverse event and an incident report form completed.

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How can I ensure that the right formulation of Comirnaty® is given to the appropriate age group?

The following checks are routinely recommended before COVID-19 vaccination:

  • Is this a primary course and what dose number is it?
  • What is the age of the person?
  • What is the recommended vaccine for this age-group?
  • What is the recommended dose?
  • What is the recommended interval since the last dose?
  • Has the person had COVID-19 infection? What is the recommended interval since laboratory-confirmed COVID-19 infection? 

In addition, NIAC recommends consideration should be given to establishing separate child friendly vaccination clinics for children. This would minimise distress in young children and reduce likelihood of vaccine error by avoiding having the adult and paediatric formulations of COVID-19 vaccines at the same venue. However, as the dose and vaccines for 6 month to 4 year olds and for 5 to 11 year olds are different, caution must still be exercised to ensure the child is receiving the correct vaccine and vaccine dose for their age group.

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This page was updated on 12 September 2023