AstraZeneca Plc’s Covid-19 vaccine, which faced a fresh onslaught of questions this week, was 76% effective in a US study -- a slightly downgraded estimate based on the latest data collected from a contentious clinical trial. The company issued the new analysis in a statement on Thursday after an independent monitoring board expressed concern that the initial efficacy of 79% relied on outdated information. The earlier reading was based on data gathered through February 17.
The data glitch may delay the shot’s ability to win US regulatory clearance, although it will likely still play a crucial role in curbing the global pandemic. The findings were based on 190 symptomatic cases that developed among the 32,449 volunteers who participated in the trial, which includes 49 cases that weren’t counted as part of the initial analysis. The company didn’t disclose how many of those cases occurred in the vaccine arm and how many in the placebo arm.
The vaccine developed with the University of Oxford protected all volunteers against developing severe disease or requiring hospitalization, according to the Cambridge, England-based company. Those aged 65 and older were 85% less likely to develop symptomatic disease if they received the vaccine in the study.