Oxford vaccine provokes immune response in all ages

A University of Oxford vaccine induces immune responses to fight COVID-19 in all age groups, new research shows.

The phase two trial found the vaccine causes few side effects and induces immune responses in both parts of the immune system in all age groups and at low and standard doses, results published in The Lancet show.

The vaccine provoked a T cell response to find and attack cells infected with the virus within 14 days and an antibody response within 28 days of the booster dose.

Phase three trials are ongoing to confirm these results – as well as how effective the vaccine is in protecting against infection with SARS-CoV-2 – in a broader range of people, including older adults with underlying health conditions.

Study lead author Professor Andrew Pollard 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.”

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 total 560 participants (160 aged 18 to 55, 160 aged 56 to 69 and 240 aged 70 or over) were split into 10 groups.

They received either the ChAdOx1 nCoV-19 vaccine at a low or standard dose, or a control vaccine (the meningococcal conjugate vaccine). Participants aged over 55 years were split into groups and given a single dose of vaccine or two doses 28 days apart.

The COVID-19 vaccine had similar immunogenicity across all age groups after a boost dose

It induced antibodies against the SARS-CoV-2 spike protein and receptor binding domain 28 days after a single low or standard dose across all age groups.

Following the booster dose, antibody levels increased at day 56 of the trial, irrespective of dose or participant age. The same was seen with levels of neutralising antibodies at day 42, two weeks after the booster vaccine dose.

By 14 days after the boost dose, 208 of 209 (more than 99%) participants (all ages and doses) had neutralising antibody responses.

T cell responses against the SARS-CoV-2 spike protein peaked 14 days after first vaccination, regardless of age and low or standard vaccine dose.

Co-author Professor Sarah Gilbert said: “Questions remain about effectiveness and length of protection, and we need to confirm our results in older adults with underlying conditions to ensure that our vaccine protects those most at risk of severe COVID-19 disease.”