New Delhi: Results of the Phase 2 clinical trials of the Covid-19 vaccine (ChAdOx1 nCoV-19) developed by Oxford University show that while the vaccine is safe and generates an immune response, it is tolerated ‘better in older adults’ than younger ones. Elderly people are among the most vulnerable populations during the pandemic.
“ChAdOx1 nCoV-19 appears to be better tolerated in older adults than in younger adults and has similar immunogenicity across all age groups after a boost dose. Further assessment of the efficacy of this vaccine is warranted in all age groups and individuals with comorbidities,” the researchers have concluded in the paper published in the medical journal The Lancet.
Professor Andrew Pollard from University of Oxford, UK, who is the lead author of the study, 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.”
Between 30 May and 8 August, 560 participants were enrolled for the trial to receive either two doses of the trial vaccine or two doses of a meningitis vaccine. While reactions were more common in participants given ChAdOx1 nCoV-19 than in those given the control vaccine, they were less common in the older adults — people over 56 years. The reactions included feeling feverish, muscle ache and headache. Immunogenicity, however, was similar across all age groups.
The co-author of the study, Dr Maheshi Ramasamy, University of Oxford, UK, adds: “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.”
ChAdOx1 nCoV-19 is made from a virus (ChAdOx1), which is a weakened version of a common cold virus (adenovirus) isolated from chimpanzees. It has been developed at the Jenner Institute in England.
Serious adverse events unrelated to vaccine
The Oxford vaccine trial had been stalled after one participant reported an adverse reaction. In the paper, the researchers wrote: “The serious adverse events observed during the trial in these study groups were judged to be unrelated to the study vaccines and occurred at frequencies expected for these conditions in the general population. None of the participants included in this report had any suspected unexpected serious adverse reactions.
“In the phase 3 component of the trial, suspected unexpected serious adverse reactions occurred in other groups, and will be reported in detail in a subsequent publication. We carefully monitored suspected unexpected serious adverse reactions and other adverse events to ensure that no pattern of unexplained illnesses emerged that could indicate a safety concern. Independent assessments have led to the recommendation that the trial is safe to continue.”
The vaccine induced a specific antibody response to the SARS-CoV-2 spike glycoprotein at 28 days after a single dose across all age groups, including adults aged 70 and above. This, the researchers wrote, is “encouraging” because many vaccines, including that for influenza, generate a milder immune response in older people.
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