'Encouraging' Results for Older People From Oxford COVID-19 Vaccine

Peter Russell

November 19, 2020

The SARS-CoV-2 vaccine developed by the University of Oxford has shown an encouraging immune response in older adults, according to preliminary findings published in The Lancet.

In phase 2 trials of ChAdOx1 nCoV-19, similar safety and immunogenicity results were seen in healthy participants aged 56 years and older to those seen in adults aged 18 to 55.

The study also suggested that the vaccine, being developed in partnership with AstraZeneca, was better tolerated in older people compared to younger adults.

Further Trial Results 'By Christmas'

Interim results from larger scale phase 3 trials, that could indicate whether the Oxford vaccine can prevent people from developing COVID-19, are expected in the coming weeks.

Prof Andrew Pollard, who is leading the study, said today he was "confident that we'll have results of the phase 3 studies before Christmas".

Early results from Pfizer-BioNTech and Moderna published this month have indicated that their messenger RNA (mRNA) vaccines have proved around 95% protective.

However, Prof Pollard told a briefing hosted today by the Science Media Centre, that it was "not a competition" and that his team were working to produce "very high quality data" on its chimpanzee adenovirus-vectored vaccine.

Immune Response

Results from the phase 2 trial of ChAdOx1 nCoV-19 indicated that the vaccine induces neutralising antibodies and T-cell responses in all age groups from 18 to 70+ irrespective of whether participants received one or two doses.

A T-cell response peaked at 14 days after the first dose of vaccination, and an antibody response within 28 days of the booster dose of vaccination.

The phase 2 trial of the vaccine was evaluated in 560 healthy adult volunteers.

Of those, 160 were aged 18 to 55, 160 aged 56 to 69 years, and 240 aged 70 or over. Participants were split into 10 groups where they received either the ChAdOx1 nCoV-19 vaccine at a low or standard dose, or a control meningococcal conjugate vaccine.

Those aged over 55 years were also split into groups and either given a single dose of vaccine, or two doses 28 days apart.

Well-tolerated in Older People

Dr Maheshi Ramasamy, principal investigator at the Oxford Vaccine Group, said side effects "were those that we normally see after a flu vaccine, or any other vaccines – so, tiredness, headaches, muscle aches".

The data clearly showed that "as you got older, the symptoms were less troublesome", she added.

The early findings are likely to boost hopes that prioritising older people for vaccination could be justified. However, doubts remain whether older people in care homes would respond as well as the healthy older adults in the trial.

Participants were "not representative of the most frail and most vulnerable in our community," acknowledged Dr Ramasamy.

The UK Government has ordered 100 million doses of the Oxford vaccine. That is more than the 40 million doses of the Pfizer-BioNTech vaccine, and the five million of the Moderna vaccine.

'Encouraging' Results

Commenting on the study, Dr Michael Head, senior research fellow in global health at the University of Southampton, said: "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 [of] a successful COVID-19 vaccine."

Deborah Dunn-Walters, professor of immunology at the University of Surrey, called the results "encouraging". She said: "The vaccine appears to be well tolerated in all age groups, with older individuals reporting fewer side-effects. 

"At one month after giving two doses of the vaccine, all age groups showed a similar level of antibody response. 

"Some age-related differences in the cellular immune response were recorded which require further investigation. 

"However, if the immune measures recorded in the phase 2 part of this study correlate with protection from SARS-CoV-2, then we would expect positive outcomes from the phase 3 trial."

Lancet. Safety and immunogenicity of ChAdOx1 nCoV-19 vaccine administered in a prime-boost regimen in young and old adults (COV002): a single-blind, randomised, controlled, phase 2/3 trial. Published:November 18, 2020 doi.org/10.1016/S0140-6736(20)32466-1

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