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Behind the headlines: the COVID-19 vaccine dosing schedule

11th February 2021 // Caroline Donoghue

Over the last few months there have been numerous news reports about COVID-19 vaccines discussing everything from vaccine effectiveness to vaccine supply. Sometimes, it is hard to know when a news story is a lively debate or when it is new news about a change that impacts you.

One topic Myeloma UK has been actively following and interrogating is the guidance on the vaccine dosing schedule. We have been monitoring the clinical evidence and recommendations defining who gets the vaccine and when, how the vaccines will be given, whether people will get one dose or two, and how far apart vaccine doses should be.

The guidance on this has been updated several times and is still being debated by clinicians and medical experts. Iis hardly surprising, therefore, that there is some confusion around vaccine administration, what to expect, and whether there is any specific guidance for clinically extremely vulnerable people.

Let’s start with the easy question – should you get one dose or two?

The clinical evidence tells us that two doses are required for long lasting protection against COVID-19 and therefore, for best results, two doses should be administered.

It is clear from this announcement and the current recommendations from the Joint Committee for Vaccination and Immunisation (JCVI) that everyone should get two doses of the COVID-19 vaccine. In most cases, this will be two doses of the same vaccine.

The number of doses remains the same, but recently changes have been made to extend the timing between doses to facilitate the priorisitisation.

This leads us to the second question – how far apart should the doses be?

The current advice states that for operational reasons (i.e. to allow vaccine services to prioritise first doses) the second dose of both the Pfizer/BioNTech and Oxford/AstraZeneca vaccines should be routinely scheduled between four and 12 weeks after the first dose. However, the UK Government’s delivery plan stated that the second doses of vaccines will be given towards the end of that dosing schedule. Therefore, most people will get their second dose 12 weeks after their first.

This change to the dosing schedule generated a lot of news and debate within the scientific community.

Much of the debate focused on the Pfizer/BioNTech vaccine. This is because there was limited clinical evidence to determine whether the change in dosing schedule would change the effectiveness of the vaccine. The people in the clinical trial received the second dose after three weeks, not at 12 weeks, which begs the question, how do they really know that it will still work at 12 weeks?

Well, this is where the clinical data, existing knowledge of vaccines, and the immune system and statistics come into play. Medical experts combine all the data and evidence to make a statistical model to predict the outcome of the proposed change.

Statistical modelling is used regularly in health decision making. For instance, it was used to determine the vaccine priority list and it is why a myeloma patient of any age is grouped, in terms of COVID-19 risk, with those 70 years old and up. This method is also used in drug appraisals where data is not as complete as everyone would like.

Outcomes from the statistical model developed by the JCVI were shared in their evidence statement supporting the widening of the dosing schedule. It was estimated that the short-term protection from one dose of Pfizer/BioNTech vaccine was 90% and that the long-term protection following the second dose was expected to be as or more effective when delivered at an interval of 12 weeks from the first dose.

The model developed by the JCVI has not been published so there is still some debate and discussion surrounding the dosing schedule. However, to me, this debate is not black and white – it is not a question of will it work or not work. In both scenarios the vaccine will provide good protection against COVID-19. So, to me, it is about getting the right balance, ensuring all vulnerable people get vaccinated quickly and in the best possible way.

However, the widening of the dosing schedule presented challenges for those clinicians planning and managing treatment for clinically extremely vulnerable patients. Clinicians needed more flexibility in the dosing schedule to ensure patients did not need to choose between the vaccine and their treatment. 12 weeks is a long time to wait for cancer treatment.

Therefore, changes were made to increase the flexibility around the dosing schedule for those due to start any treatment or medical procedures which would weaken the immune system. The guidance change means that anyone due to start immunosuppressing treatment should receive both doses of the vaccine at least two weeks before starting treatment. To enable this, the second dose can be given at the recommended minimum of three or four weeks from the first dose. Furthermore, any patients scheduled to receive immunosuppressing treatment not already on the clinically extremely vulnerable list will now be prioritised along with clinically extremely vulnerable people.

Whilst the impact of the change for myeloma patients in remission or currently receiving immunosuppressing treatments may be small, I think it gives clinicians some flexibility and an opportunity to put forward a case for a shorter time frame between doses, closer to four weeks than 12, where there is a clear benefit for patients. This could be patients at risk of becoming more immunosuppressed due to treatment changes or signs of relapse, patients with a high risk of COVID-19 exposure due to a planned medical procedure or regular hospital visits, or a patient whose medical procedure is being pushed back until after vaccination is complete.

If you feel that you fall into this category it is worth talking to your haematologist to see if they think the second dose of your COVID-19 vaccination should be brought forward.

All myeloma patients are classed as clinically extremely vulnerable therefore most patients should have had their first dose of the vaccine. You can find out more about the vaccination programmes across the UK and how to book and/or manage your vaccination appointments via the NHS website.