LONDON (UK) – Britain said on Thursday that the world could face around 4,000 variants of the COVID virus. This has prompted a race to improve vaccines with researchers starting to explore mixed doses of the Pfizer and AstraZeneca shots.
Apart from the British, South African and Brazilian variants which appear to spread more swiftly than others, thousands of variants have been documented as the virus mutates.
“Its very unlikely that the current vaccine won’t be effective on the variants whether in Kent or other variants especially when it comes to severe illness and hospitalisation,” said British Vaccine Deployment Minister Nadhim Zahawi.
“All manufacturers, Pfizer-BioNTech, Moderna, Oxford-AstraZeneca and others, are looking at how they can improve their vaccine to make sure that we are ready for any variant – there are about 4,000 variants around the world of COVID now.”
According to the British Medical Journal, while thousands of variants have arisen as the virus mutates on replication, only a very small minority are likely to be important and to change the virus in an appreciable way.
The so called British variant, known as VUI-202012/01, has mutations including a change in the spike protein that viruses use to bind to the human ACE2 receptor – meaning that it is probably easier to catch.
“We have the largest genome sequencing industry – we have about 50% of the world’s genome sequencing industry – and we are keeping a library of all the variants so that we are ready to respond – whether in the autumn or beyond – to any challenge that the virus may present and produce the next vaccine,” Zahawi said.
Britain on Thursday started a first-of-it’s-kind trial to assess the immune responses generated if doses of the vaccines from Pfizer and AstraZeneca are combined in a two-shot schedule. Initial immune response data is expected to be generated around June.
The trial will examine the immune responses of an initial dose of Pfizer vaccine followed by a booster of AstraZeneca’s, as well as vice versa, with intervals of four and 12 weeks.
AstraZeneca’s shot is separately being trialled in combination with another viral vector vaccine, Russia’s Sputnik V.
Matthew Snape, an Oxford vaccinologist who is leading the trial, said mixing different shots had proven effective in Ebola vaccine schedules, and though the new trial mixed vaccine technologies, it could also work.
“Ultimately, it all comes down to the same target – cells making the spike protein – just using different platforms,” he told reporters.
“For that reason we do anticipate that we’ll generate a good immune response with these combinations.”
Public Health England’s head of immunisation Mary Ramsay said there was a lot of precedent for such work, as vaccines against Hepatitis A and B were interchangeable from two different manufacturers, and similar work has been undertaken for human papillomavirus (HPV).