This information is sourced from: NHSE, GOV UK, The Green Book Chapter 14a, PHE, FDA,

Guidelines on location and timing of second doses and when to use an alternative vaccine to the first dose

Location

Generally people in all cohorts should be given dose 2 at the same site as they had dose 1 (i.e. if given via GP it should be given at the same PCN/surgery)

If booked through the National Booking Service there is an option to book dose 2 at an alternate site

There are circumstances where it can be appropriate for a patient to receive their second dose in a different location to their first dose, (for example, patients discharged from hospital since dose 1, students, doctors in training on rotation, people who have become housebound or patients who have moved a long way away from where they had their first dose). It’s best to take a common-sense approach to these cases

Timing of second dose

On 14 May 2021, the JCVI recommended that the second dose interval be brought forward from 12 to 8 weeks for people in priority cohorts 1-9 who have yet to receive their second dose due to delta variant cases increasing. Second doses for cohorts 1-9 should take place at 56-63 days (8-9 weeks). For people in cohorts 10 onwards, the agreed dose interval period remains as previously, at 77-84 days (11-12 weeks) The clinical evidence for the AstraZeneca vaccine shows better efficacy following a 12-week gap, which is the basis of the JCVI recommendation.

If in exceptional circumstances there is vaccine at the end of a clinic which may be wasted, sites may bring forward cohort 10 onwards second doses (as per the Green Book). This should be as close to 12 weeks as possible and as a minimum at least eight weeks after the first dose as recommended by JCVI

There are a small number of patients who are about to commence immunosuppressive therapy and, where clinically appropriate, should be considered for vaccination prior to this (ideally at least two weeks before), when their immune system is better able to make a response

Where possible, it would also be preferable for the two-dose-schedule to be completed prior to commencing immunosuppression i.e. offering the second dose at the recommended minimum interval (4 weeks for AZ and Moderna, 3 weeks for Pfizer) to provide maximum benefit that may not be received if the second dose was given during the period of immunosuppression.

For homeless patients and rough sleepers  in order to maximize coverage, JCVI also advise a first vaccine dose should be given, even if follow up for a second dose is likely to be uncertain, and that the dosing schedule can be compressed if that makes delivery of a second dose more certain.  If an interval longer than the recommended interval is left between doses, the second dose should still be given. The course does not need to be restarted

What if dose 2 is given too early?

If the second dose of the Pfizer vaccine is given less than 19 days after the first dose, the dose should be discounted and another dose (a third dose) should be given at least 21 days after the dose given too early. The 19-day interval is the minimum interval that was used in the clinical trials

If the second dose of the AstraZeneca or Moderna vaccine is given at less than the recommended 28 day interval, but at least 21 days after the first dose, it does not need to be repeated. If the second dose is given less than 21 days after the first, it should be discounted and another dose (a third dose) should be given at least 28 days after the dose given too early

What vaccine should be offered as dose 2?

JCVI and Green Book recommendation is that the same vaccine is given for doses 1 and 2 ie AZ/AZ, Pfizer/Pfizer.  There are exceptions to this rule:

• If the patient cannot recall and it is not able to be determined which vaccine was given as dose 1 (and every effort is made to find out)
• If a patient has Pfizer as dose 1 then for example becomes housebound rendering them unable to have the Pfizer vaccine as dose 2 (storage issues) they can have AZ as dose 2
• Those who had anaphylaxis to dose 1 of any vaccine can have another vaccine IF advised by an allergy specialist.
• Anyone who had VITT after dose 1 AZ should not receive dose 2 as AZ
• If their original vaccine is no longer available locally they can have an alternative, however, the hope is that vaccines can be shared across PCNs and vaccination centres to avoid this (vaccine mutual aid policy

Despite VITT issues all those who have received a first dose of the AstraZeneca vaccine should continue to be offered a second dose of AstraZeneca vaccine, irrespective of age.

What if the initial vaccine was given overseas?

• If a person has received a first dose of a COVID-19 vaccine overseas that is also available in the UK, they should receive the same vaccine for their second dose
• If the vaccine they received for their first dose is not available in the UK, the most similar alternative should be offered (see table)
• Any overseas vaccination should be recorded in the patient’s GP care record. If the patient presents at a Hospital Hub or Vaccination Centre, they should be advised to inform their GP of their previous vaccination so that their own practice can add these details.
• If the vaccine received overseas is not listed in the table, a full course of the appropriate vaccine recommended for the individual in the UK (which may depend on their age) should be given

The various groups of vaccines are:

• Adenovirus (ChAdOx) vector: AstraZeneca, Covishield
• mRNA: Pfizer, Moderna
• whole inactivated Coronavirus: Sinopharm, Sinovac, Covaxin

The other adenovirus-based vaccines (Janssen, Sputnik, CanSinoBio) use different vectors and so are not immunologically the same as either the AstraZeneca or Covishield adenovirus vector vaccines. However, as they, and the Novavax vaccine, are all based on spike protein, the vaccine course can be completed with any of the locally available vaccines as appropriate for the individual’s age.

See table for details of what alternative vaccine to offer if the vaccine received as dose one is not locally available.

COVID-19 vaccine and clinical trial participants

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

By Dr Carrie St John-Wright