Imperial College London, once a leading UK contender in the Covid-19 vaccine race, has dropped plans for a large-scale efficacy trial this year.

Instead the university’s team will focus its RNA technology on developing next-generation jabs that would target coronavirus mutations and provide boosters for existing vaccines.

Professor Robin Shattock, the project leader, said the change of direction did not reflect disappointing results from phase 1 and 2 clinical trials, which have involved more than 400 volunteers.

“Although our first generation Covid-19 vaccine candidate is showing promise in early clinical development, the broader situation has changed with the rapid roll out of approved vaccines,” he said.

“It is not the right time to start a new efficacy trial for a further vaccine in the UK, with the emphasis rightly placed on mass vaccination in response to the rapid spread of the new variant.”

The Imperial technology is based on “self-amplifying RNA” or saRNA. This is similar to the mRNA vaccines from Moderna and BioNTech/Pfizer — injecting genetic instructions to make viral proteins, which prime the immune system to fight future infection.

But, unlike the others, the Imperial vaccine makes multiple copies of its RNA inside human cells, which means that much smaller doses are needed. Another difference is that it is stable at ordinary fridge temperatures and does not require storage in a deep freeze like other mRNA vaccines.

“We want to develop Imperial’s technology as a safety net to catch escape mutations, reach variants that other vaccines may not and meet potential needs for annual booster vaccinations,” Prof Shattock said. “We are also providing the UK with long-term capability in RNA vaccines for Covid-19 and other potential infectious threats.”

The Imperial scientists are already developing saRNA vaccines to target other lethal viruses that could pose pandemic risks to the world, including Ebola, Marburg and Lassa fever.

Last spring people were talking about the Imperial project alongside Oxford’s vaccine as the two great UK candidates to inoculate the world against Covid-19.

The Oxford vaccine proceeded faster, Prof Shattock said, both because its adenovirus-based technology was more advanced than Imperial’s saRNA and because it was much more generously funded by the government and its pharmaceutical industry partner AstraZeneca.

The same applied to the research and development investment by the US and German governments in the Moderna and BioNTech vaccines. “We received £18m last year from philanthropists and the UK government, which pales into insignificance compared to the billions paid to the others,” he said.

With RNA inoculation now certain to be a key strand in the future of the global vaccines industry, Prof Shattock said it was essential for the UK to build up development and production capacity in the area.

“We are already seeing that it is problematic to rely on vaccine manufacturing in Europe and elsewhere in the world,” he said. “The export restrictions being discussed this week should be a wake-up call.”

Doug Brown, chief executive of the British Society for Immunology, welcomed Imperial’s change of strategy. “The team there has clearly thought long and hard about this,” he said, “and it will be great to see their technology continue to develop.”