Covid: Why we don't yet know if the Oxford vaccine is the Christmas cracker we hoped for

Tom Clarke

Former Science Editor

Oxford's Covid vaccine has shown promising early results. Credit: PA

Promising news, but we don’t know if the Oxford vaccine is a Christmas cracker yet. I don’t want to come across all Grinch-like, but today’s headlines about the Oxford Covid vaccine is not the news we’ve all been waiting for. Christmas definitely came early for all of us with the astonishingly good results reported in huge clinical trials of Pfizer, Moderna and Sputnik COVID vaccines.

But today’s evidence from Oxford isn’t the same. It’s like shaking the present before we’ve been able to open it - a good hint the vaccine will be just what we’ve always wanted, but it's not the proof we need.

On Thursday, the Lancet published the early data from the Oxford group’s Phase 2 clinical trial carried out months ago.

The one where they looked for any adverse safety issues in more than 500 people. It’s a big enough sample size to rule out any major safety issues with the vaccine. And, crucially, the researchers wanted to know if it might work in older people who are most at risk of severe Covid. So they included 200 people over 70 to be given the jab.

The results were as good as they could have hoped for. The vaccine produced fewer side-effects (like temporary fatigue) in the older age group, and blood samples proved it prompted a powerful immune response. But since that work was done the trial has been expanded to include tens of thousands of individuals — a Phase 3 trial.

A team of experts at the University of Oxford working to develop a vaccine that could prevent people from getting Covid-19 Credit: Sean Elias/PA

And only one of those can answer the ultimate question: does the vaccine actually protect people from getting sick with Covid?

Because only a Phase 3 trial includes enough people - and runs for long enough for the volunteers included to actually catch Covid - and therefore prove whether your vaccine works or not. The chances are it will. The data from Pfizer, and Moderna showed vaccines do work. The Sputnik V data from Russia is even more encouraging for Oxford because, like their technology, the vaccine uses a harmless adenovirus to shuttle Covid antigens into the body, proving the approach works in principle. But only Oxford’s Phase 3 data, which we’re expecting imminently, will prove whether their vaccine works.

And given the UK has bet most heavily on the Oxford vaccine in terms of investment and numbers of doses ordered, a positive result will be the Christmas present we’ve all been waiting for.