UK Launches 1st COVID Vaccine Alternating Dose (heterologous prime-boost) Vaccination Study

Credit ACIP/CDC

#15,784

Right now, if you get a a Moderna, or Pfizer, or some other manufacturer's COVID vaccine for your first shot, you are expected to get your second (booster) shot from the same manufacturer (a homologous prime-boost).

That's how these vaccines were tested, and the only data we have is based on this practice. 

But this raises some logistical issues, as it requires scheduling a second shot that matches your first.  If supplies of your vaccine are temporarily in short supply, you might have trouble getting your booster shot.  Things become even more difficult if a 3rd or 4th booster is eventually needed to handle emerging variants. 

It is important to know if these vaccines remain safe and effective when interchanged. 

There is even some evidence to suggest that a heterologous prime-boost might be more effective than a homologos prime-boost.

In 2019, a report in Nature's Scientific Reports found a synergy between heterologous Hepatitis B vaccines (in mice) which may help overcome chronic HBV infection (see Synergy of therapeutic heterologous prime-boost hepatitis B vaccination with CpG-application to improve immune control of persistent HBV infection). 

Details on this latest study were published this morning by the UK's Department of Health and Social Care.   Initially, 8 combinations of vaccines will be tested - across more than  800 patients - in this planned 13-month study.

World-first COVID-19 alternating dose vaccine study launches in UK

The study will examine whether different vaccines can safely be used for 2-dose regimes in the future.

Published 4 February 2021
From:Department of Health and Social Care

• Clinical trial looking into alternating COVID-19 vaccine doses launched today in the UK
• Current programme of 2 doses of the same vaccine over 12 weeks remains unchanged
• Innovative study backed by £7 million of government funding

Patients taking part in a new clinical study launching today will soon receive different COVID-19 vaccines for their first or second dose.

Backed by £7 million of government funding, the study will be the first in the world to determine the effects of using different vaccines for the first and second dose – for example, using Oxford University/AstraZeneca’s vaccine for the first dose, followed by Pfizer/BioNTech’s vaccine for the second.

The study, run by the National Immunisation Schedule Evaluation Consortium (NISEC) across 8 National Institute for Health Research (NIHR) supported sites, will also gather immunological evidence on different intervals between the first and second dose for a mixed-vaccine regimen against control groups when the same vaccine is used for both doses.

A same-dose regimen is currently implemented for the national COVID-19 vaccination programme, and there are no current plans for this to change. Anyone who has received either the Pfizer or AstraZeneca vaccination as part of the UK-wide delivery plan will not be affected by this study. They will receive their second dose from the same source and over the same 12-week interval.

The 13-month study will monitor the impact of the different dosing regimens on patients’ immune responses, which have the potential to be higher or lower than from the same dose regimen. Initial findings are expected to be released in the summer. The study has received ethics approval from the Research Ethics Committee, as well as approval from the Medicines and Healthcare products Regulatory Agency (MHRA).

Should the study show promising results, then the government may consider reviewing the vaccine regimen approach if needed, but only if proven to be safe and recommended by the Joint Committee on Vaccination and Immunisation (JCVI).

Minister for COVID-19 Vaccine Deployment, Nadhim Zahawi, said: 

This is a hugely important clinical trial that will provide us with more vital evidence on the safety of these vaccines when used in different ways.

Nothing will be approved for use more widely than the study, or as part of our vaccine deployment programme, until researchers and the regulator are absolutely confident the approach is safe and effective.

This is another great step forwards for British science, expertise and innovation, backed by government funding – and I look forward to seeing what it produces.

Deputy Chief Medical Officer and Senior Responsible Officer for the study, Professor Jonathan Van-Tam, said:

Given the inevitable challenges of immunising large numbers of the population against COVID-19 and potential global supply constraints, there are definite advantages to having data that could support a more flexible immunisation programme, if needed.

It is also even possible that by combining vaccines, the immune response could be enhanced giving even higher antibody levels that last longer; unless this is evaluated in a clinical trial we just won’t know.

This study will give us greater insight into how we can use vaccines to stay on top of this nasty disease.

The study will initially have 8 different arms testing 8 different combinations, but more products may be added. The 8 arms include:

• 2 doses of the Oxford/AstraZeneca vaccine at 28 days apart
• 2 doses of the Oxford/AstraZeneca vaccine at 12 weeks apart – as a control group
• 2 doses of the Pfizer/BioNTech vaccine at 28 days apart
• 2 doses of the Pfizer/BioNTech vaccine at 12 weeks apart – as a control group
• the Oxford/AstraZeneca vaccine for the first dose, followed by the Pfizer/BioNTech vaccine for the second, at 28 days apart
• the Oxford/AstraZeneca vaccine for the first dose, followed by the Pfizer/BioNTech vaccine for the second, at 12 weeks apart
• the Pfizer/BioNTech vaccine for the first dose, followed by the Oxford/AstraZeneca vaccine for the second, at 28 days apart
• the Pfizer/BioNTech vaccine for the first dose, followed by the Oxford/AstraZeneca vaccine for the second, at 12 weeks apart

Over 800 patients are expected to take part in the study, referred to as the COVID-19 Heterologous Prime Boost study or ‘Com-Cov’, across 8 different sites across England – including in London, Birmingham and Liverpool.

Patients will be recruited over the course of February via the NHS COVID-19 Vaccine Research Registry, with vaccinations expected to start towards the middle of the month and initial results to be made available over the summer period. The UK public can volunteer to be contacted about taking part in the study and further vaccine studies by joining the registry.

The study has been classified as an Urgent Public Health study by the NIHR and is being undertaken by NISEC and the Oxford Vaccine Group, with funding of £7 million from the government through the Vaccines Taskforce.

(Continue . . . )