Covid: Oxford vaccine shows 'encouraging' immune response in older adults

A third phase of testing among a larger group of people is underway and early results are expected in the coming weeks.

After reporting strong antibody levels in Phase 2 trials, Moderna and Pfizer in recent days announced preliminary Phase 3 efficacy rates above 90 percent, a result greeted with enthusiasm from the medical world.

The ongoing pandemic has seen numerous countries race for an effective vaccine against COVID-19, with Sinovac running phase 3 trials in Brazil, Indonesia and Turkey, Reuters reported.

The Pfizer vaccine is now furthest ahead and Albert Bourla, the chief executive of the pharmaceutical company, said submissions to regulators would be made within days and shipping would begin "a couple of hours" after it was given the green light.

Sinopharm's vaccines, which use inactivated virus unable to replicate in human cells to trigger immune responses, require two doses, clinical trial registration data showed.

Phase 1 and 2 trials are not created to show efficacy, says Dr. Kirsten Lyke, an immunologist and medical professor at the University of Maryland School of Medicine.

CoronaVac is one of the 48 vaccine candidates for Covid-19 that are now in clinical trials.

The Oxford-AstraZeneca COVID-19 vaccine candidate, called AZD1222 or ChAdOx1 nCoV-19, had been among the front-runners in global efforts to develop shots to protect against infection with the novel coronavirus, or SARS-CoV-2.

They show that older adults aged 56-69 and over 70 had a similar immune response to younger adults aged 18-55.

According to the study, stronger antibody responses were produced with doses given on day 0 and 28 of the trial.

Volunteers in the trial were put into groups and given one or two doses of the vaccine or a dummy jab.

These trial results from the University of Oxford, peer-reviewed in the Lancet, suggest that may not be a problem. It said one person had a severe reaction of hives and recovered within three days with treatment. This is the last stage before seeking regulatory approval, and includes tracking the effectiveness of the vaccine in preventing coronavirus. The companies, Moderna and Pfizer, have said they will seek emergency use authorization for their vaccines from the U.S. Food and Drug Administration (FDA).

Prof Andrew Hayward - director of the UCL Institute of Epidemiology and Health Care and a member of the government's Scientific Advisory Group for Emergencies - told the BBC that family gatherings at Christmas would pose "substantial risks".