Phase 2 trials of Oxford University's COVID-19 vaccine in healthy older adults have found it is safe and provokes an immune response.
The university confirmed that the candidate vaccine it is developing with AstraZeneca showed similar safety and immunogenicity results in healthy older people (aged 56 and over) to those seen in adults aged 18-55 years.
Older people are at a disproportionate risk of severe COVID-19 disease, so it is essential that any vaccine adopted for use is effective in this group.
The early-stage results, which they described as "promising" were published Thursday in The Lancet medical journal.
The phase 2 trial, which involved 560 adults including 240 over the age of 70, found that the vaccine causes few side effects and induces immune responses in both parts of the immune system in all age groups.
Results showed within 14 days of the first dose of vaccination it provoked a T cell response — it could find and attack cells infected with the virus — and caused an antibody response within 28 days of the booster jab.
Phase 3 trials, which involve thousands of participants, are ongoing to confirm these results, as well as how effective the vaccine is in protecting against infection with SARS-CoV-2 (the strain of the virus that causes coronavirus disease) in a broader range of people, including older adults with underlying health conditions, according to the vaccine's developers
"Immune responses from vaccines are often lessened in older adults because the immune system gradually deteriorates with age, which also leaves older adults more susceptible to infections," said study lead author, Professor Andrew Pollard from the University of Oxford.
"As a result, it is crucial that COVID-19 vaccines are tested in this group who are also a priority group for immunisation."
Late-stage trial results will show if the Astra-Oxford vaccine can meet the standard set by front-runners Pfizer-BioNTech and Moderna.
Pfizer and BioNTech said Wednesday that coronavirus vaccine they were developing has been proved 95% effective overall, with efficacy in adults over 65 years of age at 94%.
The US and German pharmaceuticals organisations said the candidate now met the safety criteria needed for emergency authorisation.
US biotechnology company Moderna said on Monday that, based on preliminary data, their potential coronavirus vaccine has been deemed to be 94.5% effective at preventing people from getting the virus.
Trials for the Astra-Oxford vaccine candidate were paused in September after a participant fell ill.
They were restarted again after the company had investigated whether a vaccine recipient's "potentially unexplained” illness was a result of receiving the jab.
In large trials like this one, "it is expected that some participants will become unwell and every case must be carefully evaluated to ensure careful assessment of safety," the Oxford University said.
It did not disclose medical information about the illness that caused the trial to be put on hold, citing participant confidentiality.
Health experts, including the UK government's chief scientific adviser, Sir Patrick Vallance, have said pauses in drug trials are commonplace to ensure safety and effectiveness.