The University of Oxford is expected to release data on the efficacy of its coronavirus vaccine, ChAdOx1 in the coming weeks as the trial results suggest that the vaccine produces a strong immune response in healthy adults aged 56-69 and over 70.
According to Researchers, The Lancet phase two findings, based on 560 healthy adult volunteers, are “encouraging”. The trial demonstrated similar immune responses across all three age groups – 18-55, 56-69, and 70 and over.
Volunteers received two doses of the vaccine candidate or a placebo meningitis vaccine. No serious adverse health events related to the vaccine were seen in the participants. The results are consistent with phase 1 data reported for healthy adults aged 18-55 earlier this year.
Dr Maheshi Ramasamy, an investigator in the Oxford Vaccine Group and a consultant physician, said: “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, but 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.”
The study’s lead author, Prof Andrew Pollard, from the University of Oxford, said: “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. As a result, it is crucial that Covid-19 vaccines are tested in this group who are also a priority group for immunisation.”
Ramasamy added: “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.”
Researchers say their findings are promising as they show that older people are having a similar immune response to younger adults.
The study also found that the vaccine, being developed with AstraZeneca, was less likely to cause local reactions at the injection site and symptoms on the day of vaccination in older adults than in the younger group. Adverse reactions were mild – injection-site pain and tenderness, fatigue, headache, feverishness and muscle pain – but more common than seen with the control vaccine.
Thirteen serious adverse events occurred in the six months after the first dose was given, none of which were related to either study vaccine.
The authors note some limitations to their study, including that the participants in the oldest age group had an average age of 73-74 and few underlying health conditions, so they may not be representative of the general older population, including those living in residential care settings or aged over 80.
Phase 3 trials of the vaccine are ongoing, with early efficacy readings possible in the coming weeks.
The UK government has ordered more of the Oxford vaccine, manufactured by AstraZeneca, than any other – 100 million doses – compared to 40 million doses of the Pfizer-BioNTech vaccine and five million of the Moderna vaccine.
Three vaccines – Pfizer-BioNTech, Sputnik and Moderna – have already reported good preliminary data from phase three trials, with one suggesting 94% of over-65s could be protected from Covid-19.