FAQs Booster Dose

Booster COVID-19 vaccination for recommended groups who have already completed their primary course with any COVID-19 vaccine type

Frequently asked questions for vaccinators and health professionals 

Who is recommended to get a COVID-19 vaccine booster dose?

The National Immunisation Advisory Committee have advised the following:

One booster dose of an mRNA vaccine is recommended for

  • residents of long term healthcare facilities

  • people aged 16-59 years with underlying conditions

  • people aged 50 and older, and

  • health care workers

who have already completed their primary course with any COVID-19 vaccine type.

These recommendations has been accepted by the Department of Health.

Which COVID-19 vaccine is recommended?

  • People who are 30 years or older are recommended a single dose of the Comirnaty®/Pfizer BioNTech or Spikevax®/Moderna vaccine.
  • People aged 16-29 years are recommended Comirnaty®/Pfizer BioNTech vaccine, and not Spikevax®/Moderna vaccine.

This is as a precaution, because of reports of more frequent cases of myocarditis and pericarditis associated with a second dose of Spikevax®/Moderna compared to Comirnaty®/Pfizer BioNTech.

This is the recommendation regardless of the type of vaccine previously administered.

What is the vaccine dosage for a booster dose of vaccine?

  • For Comirnaty®, the recommended vaccine dose is the same as the that for the primary course i.e 0.3mls
  • For Spikevax®, the recommended vaccine dose is 0.25mls (half the dose used for the primary course)

When is the booster dose recommended?

  • The booster dose should be given after an interval of at least 5 months (six months preferred) following the last dose of an authorised COVID-19 vaccine.
  • If COVID-19 Vaccine Janssen® was given for the primary course, the booster dose may be given from at least 3 months after vaccination.

In exceptional circumstances a minimum interval of 2 months after the last dose of vaccine may be used.

Why is a booster dose recommended?

All authorised COVID-19 vaccines have high levels of vaccine effectiveness against hospitalisation, severe disease and death against both the Alpha and the Delta variants. While there is some decline in protection against infection with time from primary vaccination, high protection against severe disease is retained for at least six months.

Declines in vaccine effectiveness with an increase in breakthrough infections in those aged 65 and older, increasing with age, have been reported from Israel and the US. This decline may be due to waning immunity in older persons coupled with relaxation of non-pharmaceutical interventions and the emergence of the Delta variant.

Is there scientific evidence for a booster dose?

Pfizer reported that data in individuals who received a third dose of Comirnaty® show a favourable safety profile and robust immune responses. The additional dose elicited significantly higher neutralising antibody (NA) titres against the initial SARS-CoV-2 virus (wild type), and the Beta and Delta variants, compared to the levels observed after the two-dose primary series.

Preliminary findings of a population based booster programme of Comirnaty® to approximately one million people, shared by the Israeli Health Ministry reported that no safety concerns were identified. A similar profile of adverse events were reported, but lower rates of systemic and local reactions were reported after a 3rd dose than following the first or second doses.

Has the EMA recommended booster doses of COVID-19 vaccines?

Yes, the European Medicines Agency (EMA) has authorised booster doses of the same mRNA vaccine as that given for the primary course. The National Immunisation Advisory Committee has recommended a booster dose of an mRNA vaccine or these groups, regardless of the vaccine received as the primary course.

Is it recommended to check serology before administering a booster dose?

No. This is not recommended. There is no agreed or recommended correlate of protection (there is no agreed or recommended antibody level above which you would not vaccinate, or below which you would vaccinate).

What is the recommended timing of the booster dose in people who have had laboratory-confirmed breakthrough infection since they completed their COVID-19 vaccination course?

The booster dose should be delayed for at least six months after the laboratory-confirmed COVID-19 infection was diagnosed. Serological testing prior to giving a booster dose is not recommended as mentioned above. If it cannot be established if an individual had COVID-19 infection in the time frame they may be vaccinated.

Can the booster dose be given with flu vaccine or other vaccines?

Yes. The booster dose can be given at the same time as or at any interval before or after seasonal influenza vaccine (or any other vaccine including PPV23 vaccine). This will allow the uptake of both COVID and seasonal influenza vaccines to be optimised in these groups. The vaccines should be given in separate arms if possible.

What vaccine is recommended as a booster dose if someone has a contraindication to an mRNA vaccine?

A booster adenoviral vector vaccine (COVID-19 Vaccine Janssen®) can be considered for those with a contraindication or precaution to an mRNA vaccine. This includes pregnant women.

Additional resources 

This page was added on 26 November 2021