In another major boost for hopes of bringing the pandemic to heel, they said the preliminary results for the UK’s main vaccine hope were “encouraging”.
The Government has ordered 100,000 doses of the Oxford jab – the biggest proportion of the 355m doses of a portfolio of vaccines it has bought.
The phase 2 results, which focus on safety and were published this morning in The Lancet medical journal, gave data on 560 healthy adults, including 240 over the age of 70.
The crucial phase 3 results, which will reveal the vaccine’s effectiveness in tens of thousands of volunteers across several countries including the UK, are due to be published in a few weeks.
The phase 3 results will also reveal how well the vaccine works in people with underlying health conditions – those most at risk from Covid.
Phase 3 results have already been published by rival vaccine makers Pfizer/BioNtech and Moderna, both of which showed around 95 per cent effectiveness.
Today’s results from the Oxford group, which is creating the vaccine with UK-based drugs firm AstraZeneca, showed the drug was better tolerated in older people but produced a similar immune response in both young and old trial participants.
The study compared the effect on people aged 56 and older with those aged 18-55. It found there were “few side effects” and that a T-cell immune response was sparked within 14 days of the first jab, both at low and standard doses.
This means the body’s immune system could find and attack cells infected with Covid.
A subsequent booster jab kick-started an antibody response within 28 days, enabling the virus to be attacked when circulating in the blood or lymphatic system.
The Oxford vaccine has a major advantage over the Pfizer/BioNTech drug in that it does not have to be stored at around -70C prior up to a few days before being administered.
Dr Maheshi Ramasamy, one of the co-authors of the research paper at Oxford, said: “The robust antibody and T-cell responses seen in older people in our study are encouraging.
“The populations at greatest risk of serious Covid-19 disease include people with existing health conditions and older adults. We hope that this means our vaccine will help to protect some of the most vulnerable people in society, but further research will be needed before we can be sure.”
She added: “Older adults are a priority group for Covid-19 vaccination, because they are at increased risk of severe disease, but we know that they tend to have poorer vaccine responses.
“We were pleased to see that our vaccine was not only well tolerated in older adults; it also stimulated similar immune responses to those seen in younger volunteers. The next step will be to see if this translates into protection from the disease itself.”
Dr Michael Head, of Southampton university, who was not involved in the research, said: “The research also shows that an immune response was generated in all age groups, including in the cohort of participants aged above 70 years. Since elderly populations will be one of the priority groups to receive a vaccine when one is available, this is good news.
“This research is not an announcement that the vaccine is ready to be licensed and rolled out, but it is further promising research in the efforts to development a successful Covid-19 vaccine.”
This story is being updated.