Oxford-AstraZeneca Covid vaccine trial shows promise for those over 70

19 Nov 2020

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A Covid-19 vaccine candidate being developed by the University of Oxford and AstraZeneca could be effective in protecting those over 70.

Following the latest news of Pfizer and BioNTech’s vaccine breakthrough, the University of Oxford and AstraZeneca have published findings on their own Covid-19 vaccine candidate to The Lancet. The phase-two trial tested the ChAdOx1 vaccine in 560 healthy adults, of which 240 were over the age of 70.

The participants were split into groups that received either the vaccine candidate or a control vaccine, in this case the meningococcal conjugate vaccine. In the older age groups, more people received the Covid-19 vaccine than the control vaccine.

The trial found few side effects across all age groups, while inducing immune responses in both parts of the immune system at low and standard doses. A T-cell response was seen within 14 days of the first dose of the Covid-19 vaccine and an antibody response within 28 days of a second dose.

Unlike the Pfizer-BioNTech vaccine and the Moderna vaccine, which are mRNA-based, the Oxford-AstraZeneca vaccine is derived from a modified adenovirus that usually causes the common cold in chimpanzees.

Phase-three trial underway

A strong immune response was seen in older adults in this trial. The study’s lead author, Prof Andrew Pollard of the University of Oxford, said that immune responses from vaccines are often lessened in older adults due to age, so a vaccine that shows promise in those aged over 70 could be an important breakthrough.

The study’s co-author, Dr Maheshi 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.”

A phase-three trial is ongoing to confirm these results and assess the efficacy of the vaccine in a wider range of people.

Study limitations

The researchers said one of the limitations of the phase-two study was that the oldest age group had an average age of 73 to 74 years and few underlying health conditions. This may not be indicative of the general older population, especially those living in care homes.

Another limitation was the fact that almost all participants were white and non-smokers, but researchers said that these are being addressed in the phase-three trial.

Dr Melissa Andrew of Dalhousie University in Canada, who was not involved in the study, commented: “It is encouraging that more studies in older adult populations are underway and will hopefully bring opportunities to implement nuanced analyses of how underlying health status and frailty affect vaccine safety, reactogenicity, immunogenicity and efficacy in older adults in real-world settings.”

The phase-three trial of the Oxford-AstraZeneca vaccine was paused in September after one participant experienced a serious adverse reaction, but it was later given the go ahead to resume. The researchers said in the Lancet publication that 13 “serious adverse events” had occurred during the study period, but none were related to the vaccine.

Colm Gorey was a senior journalist with Silicon Republic