Coronavirus: UK to trial vaccine combos in bid to boost immunity against Covid

Government intending to launch ‘mix and match’ trial next month, says chair of UK vaccine taskforce

The UK is exploring the possibility of ‘mixing and matching’ different vaccines to see whether this can boost immunity levels against Covid-19, the government’s chief scientific adviser has said.

Known as a heterologous prime-boost, the treatment can only be administered with licensed jabs and involves using a dose each from two different vaccines.

Kate Bingham, outgoing chair of the UK’s vaccine taskforce, said the government was intending to launch a “mix and match” trial next month.

Participants in the study will receive one shot of the Pfizer-BioNTech vaccine, which was last week licensed for use by the UK’s drug regulator, and one dose of the Oxford-AstraZeneca jab — assuming it is approved in time.

The vaccine developed by Moderna will also be included if it is given the green light by the Medicines and Healthcare Products Regulatory Agency.

Sir Patrick Vallance, the government’s chief scientific adviser, said the treatment was a “pretty standard way of boosting the immune system”.

"What it means is that you give one vaccine to get the immune system triggered up and another one to then boost it further with a different vaccine — that's an established way of getting the immune system geed up,” he told Sky News on Tuesday.

"But that needs to be looked at — you can't assume that it will work. It needs to be tested properly, and that's one of the things about all of these vaccines and all of the clinical trials of medicines is you need to do the trials properly, you need to make sure you test these things."

The vaccines manufactured by Pfizer and Moderna have each been shown to be 95 per cent effective in preventing Covid-19 disease. They make use of new mRNA technology, which appears to generate a bigger antibody response than other vaccine platforms.

Questions remain over the precise efficaciousness of the Oxford/AstraZeneca jab, which is 62 per cent effective when administered as two full doses. This figure rises to 90 per cent if applied as a half dose followed by a full dose.

Under a heterologous prime-boost, doses from the different vaccines would be combined, in different orders, to help enhance the body’s immune response to Sars-CoV-2 - the virus responsible for Covid-19.

“No one’s ever done it live and since we’ll have safe vaccines available we should do that study, because then we have the ability to actually produce better immune responses,” Clive Dix, deputy chair of the UK’s vaccine taskforce, said during a scientific briefing.

“There is a slight benefit to it, too, in that if prime and boosting either way around work, it may help with the deployment, because it might just be simpler to deploy that way round, but the main reason is to get a stronger immune response.”

The UK government has ordered 100m doses of the Oxford jab, 40m doses of the Pfizer candidate and 7m Moderna shots, with the vast majority of supplies set to be delivered in the new year.

Ms Bingham said the January trials were not about making limited stocks of the vaccines go further.

“It’s not being done because of supplies,” she said. “It’s to do with trying to trigger the immune response and the durability and nothing to do with what vaccines we’ve got.”

When asked if the UK could purchase more doses, Ms Bingham said: “It depends by contract. So some we have options to extend and others we've got fixed numbers of doses.”

Health secretary Matt Hancock has meanwhile said the government is hopeful that approval for the Oxford-AstraZeneca vaccine will be granted in the coming weeks.

"We very much hope that that will get approval,” he said on Tuesday. “We hope that to come through in the next couple of weeks.

"It has to be a decision for the independent MHRA, who will only approve it if it is safe to use and effective. So that works underway. And I wouldn't expect anything for the next couple of weeks."

Ms Bingham said she was also optimistic that the vaccine will be licensed for emergency use.

The comments come as the vaccine taskforce released a report looking at its work and achievements six months after it was set-up to help in the fight against Covid-19.

According to the report, the taskforce has worked decisively and at great pace in the face of the pandemic.

Prime minister Boris Johnson said: "The approval of the Pfizer/BioNTech vaccine for use in the UK marks a momentous step in our fight against Covid-19.