Why am I being invited for a third COVID vaccine dose?

1st Sep 2021 - Rachel Kahn

This blog was published on 1 September 2021 before boosters (fourth doses) were announced for people with blood cancer. Read our more recent information about booking your third dose and booster (fourth dose) of the covid vaccine.

Who will get a third vaccine dose?

The Joint Committee for Vaccination and Immunisation (JCVI) has recommended that all people in the UK who were immunosuppressed at the time of their first or second COVID vaccine should receive a third dose to help protect them from the virus. This means that shortly, if you have any type of blood cancer and are aged over 12, you will be entitled to an additional dose of the vaccine.

As the JCVI has recommended this for everyone who was immunosuppressed when they received their first two doses, our understanding at the moment is that this will include all people with blood cancer, including those who have had treatment within the last 12 months and are now in remission, and those who have had either an allogeneic or an autologous stem cell transplant in the last 24 months. This will largely be managed by GP surgeries, however specialist input will be required for people who are currently receiving treatment to ensure the third dose is given at the most appropriate point in someone’s treatment cycle. We’ve been told it may take up to 10 days for you to receive a letter with more information about this.

What vaccine will I receive?

Those aged 18 and over will most likely be given the Pfizer vaccine, or Moderna vaccine. The JCVI have said that if there is an issue with supply of either the Pfizer or Moderna vaccine, AstraZeneca may be used. For those aged 12 to 17, the Pfizer vaccine is preferred.

Is it safe to mix the vaccines?

We know that most people with blood cancer would have had the AstraZeneca vaccine previously and will now likely receive the Pfizer or Moderna vaccine as the third dose. A recent study carried out by the University of Oxford found that giving the AstraZeneca vaccine followed by the Pfizer vaccine gave a better immune response than two AstraZeneca vaccines, although this wasn’t in people who were immunosuppressed. Although this was when the vaccines were given four weeks apart, there weren’t any safety concerns, and the study suggests that mixing vaccines may even give a better response [1]. This evidence is backed up by several other studies also [2][3].

How will I get the vaccine?

Everyone eligible for the vaccine should receive a letter from their GP outlining this. This letter is important, and you should use it to prove your eligibility for a third dose at your vaccination centre. We think that patients will be identified through GP databases in the first instance, although people having treatment might have input from their clinical team to decide the most appropriate time to give people a third dose based on their treatment. The JCVI issues guidance for the whole of the UK so this means they’ve recommended immunosuppressed people in England, Scotland, Wales and Northern Ireland are given a third dose. However, we are currently unsure of how this will be rolled out in principle.

I had antibodies to the first set of vaccines, do I need this?

Current evidence suggests that people who are immunosuppressed do not respond as well to two doses of the vaccine compared to someone who isn’t immunosuppressed. We’ve been funding research looking at how people with specific types of blood cancer respond to the vaccines and there has been some difference between groups. For example, we know that some people with chronic myeloid leukaemia tend to have a better response to the vaccine than some people with chronic lymphocytic leukaemia. However, even in people who do develop antibodies the quantity of antibodies produced tends to be lower in some people with blood cancer, compared to people who are healthy, and we don’t know how well those antibodies function. We also don’t know how long antibodies last in the blood and it’s likely their numbers decrease over time and it’s hoped that an additional dose will increase the response in some people. So, even if you developed antibodies after two vaccine doses, it’s important you still get your third. We have more information about covid vaccine efficacy and the research we're helping to fund.

I haven’t developed antibodies to previous vaccines, what makes you think an additional dose will work?

We’ve seen from studies that some people who develop no antibodies to the vaccine after the first dose, do develop antibodies after the second dose. For example, a team of researchers at the University of Birmingham found that after one dose of the vaccine, 34% of people with CLL had an antibody response to vaccination which rose to 75% after the second dose. We’re hoping that the same thing will happen here and that some people who didn’t develop antibodies, or developed low numbers of antibodies after two doses, will develop a better response to the third vaccine dose.

Why is this being called a third dose and not a booster?

The JCVI are calling this a third dose as they are recommending it be given as part of primary treatment to prevent COVID in people who are unlikely to have had a strong immune response to doses one and two. A booster on the other hand is given to everyone in certain categories regardless of their immune response. A booster vaccine is to make sure that protection does not decrease over time whereas a third dose exists for people who are unlikely to have responded as well to the first two doses of the vaccine. We've been told that if a booster programme were to be rolled out, people with blood cancer may also be entitled to a booster dose, although we're waiting for more advice from the JCVI on this.

Will I be as protected as the general public after this third?

At this stage, we’re unsure whether an additional dose will give people with blood cancer as much protection as the general public after the third dose and it will take some time to understand this. However, as we do see an increase in the number of people responding to the vaccine between dose one and dose two, we hope to see the number of people responding to the vaccines increase following a third dose.

Will I receive the flu jab at the same time?

This was a suggestion from the government initially and it may be that if some vaccination centres have supply of the flu vaccines that you will be offered one at the same time as your COVID jab. This may depend on where in the country you are being vaccinated and the set up locally. A study at the University of Bristol called ComFluCov is looking at whether it is safe and effective to give people both vaccines at the same time. The full results haven’t yet been published, but some initial data on the safety and effectiveness of this combination has been shared with the JCVI which led them to publishing guidance that stated that when people are offered boosted vaccines (but note, this is not a booster), they “should be offered a booster dose alongside the flu vaccine.”

Will my household members be given a third dose, if not is this likely in the future?

It’s not yet clear what the JCVI will recommend in relation to additional doses of the vaccine for people outside of the immunocompromised group. When the JCVI issued interim advice about the potential COVID-19 booster vaccine programme adult household contacts of immunosuppressed individuals were put in stage two of prioritisation for boosters.