Oxford COVID-19 Vaccine Triggers Robust Immune Response in Older Adults in Phase 2 Trial

The ChAdOx1 nCov-2019 coronavirus vaccine, developed by teams at the University of Oxford (Oxford, UK), has been shown to trigger a robust immune response in healthy adults aged 56-69 and those over 70 years of age, suggesting that one of the groups most vulnerable to serious illness, and death from COVID-19, could build immunity.

Older adults have been shown to be at higher risk from COVID-19 and are expected to be considered as priority for immunization should any effective vaccine be developed for the disease. Data from Oxford’s Phase 2 trial of its ChAdOx1 nCov-2019 vaccine shows that volunteers in the trial demonstrated similar neutralizing antibody titres and T cell responses across all three age groups (18-55, 56-79, and 70+). During the Phase 2 trial, the vaccine was evaluated in 560 healthy adult volunteers aged between 18-55 years, 56-69 years and aged 70 or over. Volunteers received two doses of the vaccine ChAdOx1 nCoV-19, or a placebo MenACWY vaccine. No serious adverse health events related to ChAdOx1 nCoV-19 were seen in these volunteers. These data are consistent with the Phase I data reported for healthy adults aged 18-55 early this year.


For most vaccines, older adults do not exhibit as strong a response as younger adults, and vaccine-induced antibodies commonly display a lower protective capacity. The data reported by Oxford are particularly promising, as they show that the older individuals in this study, who are more prone to serious illness and death from COVID-19, are showing a similar immune response to younger adults. Furthermore, the vaccine 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, demonstrating that assessment of the efficacy of the vaccine is warranted in all age groups. The Phase 3 trials of the ChAdOx1 nCov-2019 vaccine are ongoing, with early efficacy readings possible in the coming weeks.

“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,” said Dr. Maheshi Ramasamy, Investigator at the Oxford Vaccine Group and Consultant Physician. “We were pleased to see that our vaccine was not only well tolerated in older adults; it 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.”

“Inducing robust immune responses in older adults has been a long-standing challenge in human vaccine research,” said Dr. Angela Minassian, Investigator at the University of Oxford and Honorary Consultant in Infectious Diseases. “To show this vaccine technology is able to induce these responses, in the age group most at risk from severe COVID-19 disease, offers hope that vaccine efficacy will be similar in younger and older adults.”

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