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70 Percent Efficacy Found for Oxford COVID-19 Vaccine

FRIDAY, Dec. 11, 2020 -- The ChAdOx1 nCoV-19 vaccine has an overall efficacy of 70.4 percent, with an acceptable safety profile, according to the results of an interim analysis published online Dec. 8 in The Lancet.

Merryn Voysey, D.Phil., from the University of Oxford in the United Kingdom, and colleagues analyzed data from four ongoing blinded, randomized trials conducted across the United Kingdom, Brazil, and South Africa involving participants aged 18 years and older randomly assigned to either the ChAdOx1 nCoV-19 vaccine or control. Participants in the vaccine group received two doses containing 5 x 1010 virus particles (standard dose; SD/SD cohort); a subset in the U.K. trial received a half dose as their first dose (low-dose [LD]/SD cohort). Data from 11,636 participants were included in the interim primary efficacy analysis.

The researchers found that vaccine efficacy was 62.1 percent in the ChAdOx1 nCoV-19 group among participants in the SD/SD cohort; in the LD/SD cohort, vaccine efficacy was 90.0 percent. Across both groups, overall vaccine efficacy was 70.4 percent. Ten cases were hospitalized for COVID-19 from 21 days after the first dose; all were in the control arm and two were classified as severe COVID-19, including one death. Overall, 175 severe adverse events occurred in 168 participants (84 and 91 in the ChAdOx1 nCoV-19 and control groups, respectively). Three events were classified as possibly related to the vaccine: one each in the ChAdOx1 nCoV-19 and control groups and one in a participant who is still blinded to allocation.

"Our findings indicate that our vaccine's efficacy exceeds the thresholds set by health authorities and may have a potential public health impact," a coauthor said in a statement.

Several authors disclosed financial ties to pharmaceutical companies, including AstraZeneca, which is developing the ChAdOx1 nCoV-19 vaccine and funded the study.

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Posted: December 2020

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