Dosing information COVID-19 primary vaccination

Anna Bischler, Lead Medicines Information Pharmacist, Midlands and East Medicines Advice Service (East site)Published Last updated See all updates

Dose scheduling, actions when the intervals are longer than or less than recommended, and use of alternative brands for second doses

Dose scheduling

MHRA advice

The MHRA Information for Healthcare Professionals for individual vaccines recommends:

  • Pfizer-BioNTech as a series of two doses at least 21 days apart.
  • AstraZeneca as a series of two doses between 4 and 12 weeks apart
  • Moderna as a series of two doses 28 days apart

PHE advice

Public Health England’s Immunisation Against Infectious Disease (The Green book) states that there is evidence of better immune response and/or protection where longer intervals between doses are used. The Joint Committee for Vaccines and Immunisation (JCVI) is recommending an interval of 8 to 12 weeks between doses of all the available COVID-19 vaccines. Operationally, this consistent interval should be used for all two dose vaccines to avoid confusion and simplify booking, and will help to ensure a good balance between achieving rapid and long-lasting protection.

The main exception to the eight week lower interval would be those about to commence immunosuppressive treatment. In these individuals, the minimal intervals outlined in the MHRA advice above may be followed to ensure that the vaccine is given whilst their immune system is better able to respond.

In August 2021, JCVI recommended a third primary dose of vaccination for individuals who were severely immunosuppressed when they received their first or second dose of COVID 19 vaccination

NHS England advice

NHS England updated their guidance 6th July 2021 to advise that individuals should have their second dose brought forward from an interval of 12 weeks to 8 weeks after their first dose.

NHS England state that there are a small number of circumstances when the second dose can be given at a different time interval, for example patients due to receive planned immunosuppressive therapy, homeless people and rough sleepers.

A number of actions are necessary where the interval between doses is longer than recommended.

Public Health England’s Immunisation Against Infectious Disease (The Green book) states that if the interval between the first dose and second dose is longer than recommended, the second dose should still be given (preferably using the same vaccine as was given for the first dose). The course does not need to be restarted.

If the interval between the first dose and the second dose is longer than recommended the Patient Group Directions (PGDs) and National Protocols for each COVID-19 vaccine may be used to administer the second dose of a vaccine.

A number of vaccine dependent actions are necessary where the interval between doses is shorter than recommended.

Dose has been given less than 19 days after the first dose

Public Health England advise that the second dose should be discounted. Another dose (i.e. a third dose) should be given, at least 21 days after the discounted second dose (the dose that was given too early).

The ‘third dose’ cannot be administered under the Patient Group Direction (PGD) or National Protocol for this vaccine. A Prescription or Patient Specific Direction (PSD) is required.

Dose has been given less than 28 days but at least 21 days after the first dose

Public Health England advise that the dose does not need to be repeated.

Dose has been given less than 21 days after the first dose

Public Health England advise that the second dose should be discounted. Another dose (i.e. a third dose) should be given, at least 28 days after the discounted second dose (the dose that was given too early).

The ‘third dose’ cannot be administered under a Patient Group Direction (PGD) or National Protocol for this vaccine. A prescription or Patient Specific Direction (PSD) is required.

Using a different brand for the second dose

The Public Health England’s Immunisation Against Infectious Disease (The Green book) states that there is no evidence on the interchangeability of the COVID-19 vaccines although studies are underway.

Every effort should be made to determine which vaccine the individual received and to complete the schedule with the same vaccine; however, there are exceptional circumstances where a pragmatic approach should be pursued.

Vaccine brand unavailable

There are various reason why the same brand of vaccine may not be available (e.g. the individual attended at a different site or the site is using a different vaccine on a particular day).

Public Health England advise that it is not recommended to give a different second vaccine simply because the same vaccine is not available that day. If all efforts to enable an individual to receive the same vaccine at another time and/or location have been exhausted, it may be necessary to use a different vaccine where the risk of not vaccinating is greater than the risk of further delay e.g. where the individual is at immediate high risk or is considered unlikely to attend again.

In these instances the Patient Group Directions (PGDs) and National protocols for each COVID-19 vaccine may be used to administer the second dose where the brand differs from the first dose.

Individual received COVID-19 vaccine overseas

Overseas vaccine is available in UK

Public Health England advise that for a person who has received a first dose of COVID-19 vaccine overseas that is available in the UK, they should receive the same vaccine for their second dose. They must meet UK eligibility criteria, as detailed in the the Joint Committee on Vaccinations and Immunisations (JCVI) guidance. The Patient Group Directions (PGDs) and National protocols for each COVID-19 vaccine may be used in this circumstance.

Overseas vaccines is not available in UK

Public Health England advise that for a person who has received a first dose of COVID-19 vaccines overseas that is not available in the UK, then the most similar alternative should be offered. The Patient Group Directions (PGDs) and National protocols for each COVID-19 vaccine may be used in this circumstance.

Individual is housebound

Public Health England advise that if the patient initially had the Pfizer vaccine and has since become housebound, the AstraZeneca vaccine may be administered as the second dose because this vaccine can be transported.

In these instances the Patient Group Directions (PGDs) and National protocols for each COVID-19 vaccine may be used to administer the second dose where the brand differs from the first dose.

Adverse or allergic reactions

Public Health England advise that those patients who experienced severe adverse allergic reactions or anaphylaxis reactions with the first dose of one brand of vaccine, may be offered another brand of vaccine if advised by an allergy specialist.  Individuals who experience a clotting episode with concomitant thrombocytopenia following the first dose of AstraZeneca vaccine may be offered another brand of vaccine.

In these instances the choice of vaccine would need to be assessed on an individual basis after review by an appropriate clinician and a prescription or Patient Specific Direction (PSD) is required.  It would not be appropriate to use the Patient Group Directions (PGDs) and National protocols.

Individuals in clinical trials

Public Health England advise that individuals who are participating in a clinical trial of COVID-19 vaccines who present for vaccination should be referred back to the investigators. Eligible persons who are enrolled in vaccine trials should then be provided with written advice on whether they can be safely vaccinated in the routine programme, and when.

In these instances the choice of vaccine would need to be assessed on an individual basis after review by an appropriate clinician and a prescription or Patient Specific Direction (PSD) is required.  It would not be appropriate to use the Patient Group Directions (PGDs) and National protocols.

Information on booster vaccination

Dosing information for COVID-19 booster vaccination

Coming soon! Dosing information for reinforcing immunisation.

Use in conjunction with other material

This page should be read in conjunction with other material covering the legal mechanisms for the administration of COVID-19 vaccines.

The legal mechanisms available for giving COVID-19 vaccines and their application

A summary of the different legal mechanisms available, a priority order for the options, and advice on their application to different professional groups.

Change history

  1. Page title amended to clarify that this page covers primary vaccination only and information on third primary dose of vaccination for individuals who were severely immunosuppressed added
  1. Dosing interval advice updated in line with updates to Public Health England’s Immunisation Against Infectious Disease (The Green book) and NHS England advice related to second dose intervals being brought forward from 12 weeks to 8 weeks.
  1. Minor heading title changes
  1. Published