The AstraZeneca Oxford COVID-19 Vaccine is Safe and Provokes Immune Response

November 19, 2020
John Parkinson
John Parkinson

Phase 2 results include a large cohort of seniors in the study.

In a recent announcement, the CEO of Serum Institute of India, Adar Poonawalla, has said that the vaccine should be available for the elderly and healthcare workers as soon as February 2021 and by April for the general public. "It will probably take two or three years for every Indian to get inoculated, not just because of the supply constraints but because you need the budget, the vaccine, logistics, infrastructure and then, people should be willing to take the vaccine,” said Poonawalla. “So, these are the factors that lead up to being able to vaccinate 80-90 per cent of the population. It will be 2024 for everybody."

In a phase 2 study with nearly half of the participants being over the age of 70, the AstraZeneca/Oxford COVID-19 vaccine, ChAdOx1 nCoV-19, was found to be safe and invoke an immune response.

The trial had 560 healthy adults and 240 of the participants over 70. The vaccine provoked a T cell response within 14 days of the first dose of the vaccination, and an antibody response within 28 days of the booster dose of vaccination.

“The robust antibody and T-cell responses seen in older people in our study are encouraging,” co-author Maheshi Ramasamy, MD, University of Oxford, UK, said.

The vaccine induced antibodies 28 days after a single low or standard dose across all age groups. Following the booster dose of the vaccine, antibody levels increased at day 56 of the trial, irrespective of dose or participant age. The same was seen with levels of neutralizing antibodies at day 42, 2 weeks after the booster vaccine dose. By 14 days after the boost dose, 208 of 209 (more than 99%) participants (selected from participants of all ages and doses) had neutralizing antibody responses.

Adverse reactions to the vaccine were mild, with the most common effects being injection-site pain and tenderness, fatigue, headache, feverishness and muscle pain.

The vaccine had similar immunogenicity across all age groups after a boost dose.

“The phase 2 trial finds that 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 dose – provoking a T cell response within 14 days of the first dose of vaccination (ie, a cellular immune response, it could find and attack cells infected with the virus), and an antibody response within 28 days of the booster dose of vaccination (ie, humoral immune response, it could find and attack the virus when it was circulating in the blood or lymphatic system),” the investigators reported.

The investigational vaccine is undergoing phase 3 trials, which is conducting it looking at a broader range of people, including older adults with underlying health conditions.

“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,” Ramasamy concluded.