LONDON -- The second phase of clinical trials of a Covid-19 vaccine developed by Oxford University in England shows it is effective on people in their 60s and 70s, medical journal The Lancet reported on Thursday.
In collaboration with the pharmaceutical company AstraZeneca and other groups, the researchers tested the formula ChAdOx1 nCoV-19 in a trial with 560 healthy adults, 240 of whom were over 70 years old, to observe its impact on the immune system and potential side effects.
“Our findings show that the ChAdOx1 nCoV-19 vaccine was safe and well tolerated with a lower reactogenicity profile in older adults than in younger adults,” the researchers said. “These findings are encouraging because older individuals are at disproportionate risk of severe COVID-19 and so any vaccine adopted for use against SARS-CoV-2 must be effective in older adults.”
The preliminary results indicate that this vaccine provides "similar safety and immunogenicity” in older adults than in those between 18 and 55 years old. According to The Lancet, Phase 2 of the trial found that the antidote causes "few adverse events”, and that any side effects reported were “mild to moderate in severity, in line with our previous phase 1 study”.
“Fewer adverse events were reported after the boost vaccination than after the prime vaccination” although the vaccine’s effectiveness (termed “reactogenicity”) “reduced with increasing age”, the study found. “None of the participants included in this report had any suspected unexpected serious adverse reactions,” the Lancet said.
According to the study, the vaccine generates a response in T cells (capable of finding and attacking cells infected by the virus) within fourteen days of the first dose, and an antibody response at 28 days of the booster dose (which would attack the virus when circulating in the blood or lymphatic system).
The authors of the trial said that Phase 3 clinical trials, which are already underway, should confirm these results and determine "how effective the vaccine is in protecting against SARS-CoV-2 infection" in a broader, heterogeneous group of people, including older people with comorbidities.
Oxford researcher Sarah Gilbert said this study "answers some of the questions" raised by the World Health Organization about the need for Covid vaccines to protect older adults.
However, she said other "questions about efficacy and duration of protection" remain unanswered and the vaccine must also be tested in older people with pathologies to ensure that it protects those most at risk of serious illness.
The authors acknowledged that their experiment "has limitations," namely that the older people tested had an average age of 73 or 74 and were healthy, which does not reflect the reality in nursing homes.
In addition, they add, the majority of volunteers of any age were white and non-smokers, so the third phase of the clinical trials will be extended to people from different backgrounds.