Oxford COVID-19 vaccine safe and protective against disease, phase 3 trial results say

The first full results from interim analysis of the Oxford-AstraZeneca novel coronavirus (COVID-19) vaccine trials found the vaccine has an acceptable safety profile and is efficacious against symptomatic COVID-19 disease, with no hospitalizations or severe disease reported in the COVID-19 vaccine group so far, according to the results published earlier today in The Lancet.

The analysis found that the vaccine protects against symptomatic disease in 70 percent of cases, with vaccine efficacy of 62 percent for those given two full doses, and of 90 percent in those given a half then a full dose, both trial arms pre-specified in the pooled analysis, according to the study.

The vaccine was found to be safe, with only three out of 23,745 participants over a median of 3.4 months experiencing serious adverse events that were possibly related to a vaccine; one in the vaccine arm, one in the control arm, and one in a participant who remains masked to group allocation. All participants have recovered or are recovering and remain in the trial, the study said.

The Oxford COVID-19 vaccine uses a chimpanzee adenovirus viral vector that cannot cause disease in humans and expresses the SARS-CoV-2 spike protein. This means the vaccine delivers the spike protein genetic code into vaccinated people's cells, which then produce the protein, and teaching the immune system to recognize and attack the virus. Past trial results have found that the vaccine induces antibody and T cell immune responses and is safe in adults aged 18 years and over, including older adults, the researchers said.

The results are the first full peer-reviewed efficacy results to be published for a COVID-19 vaccine.

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