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AstraZeneca's Vaccine Data May Not Be as Good as It First Appeared

By Brian Orelli, PhD - Updated Mar 23, 2021 at 1:52PM

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Investors will have to wait for the final results from a U.S. based clinical trial.

The drama surrounding AstraZeneca's (AZN 2.75%) coronavirus vaccine seems to be never-ending. First there were issues with half doses, then with reporting data that was combined from multiple clinical trials. Now the company appears to have released interim data from a trial in the U.S. when final data was pending.

The National Institutes of Health's National Institute of Allergy and Infectious Diseases (NIAID) reported on Tuesday that it had been told by the Data and Safety Monitoring Board (DSMB) for AstraZeneca's U.S. clinical trial that the board "expressed concern that AstraZeneca may have included outdated information from that trial, which may have provided an incomplete view of the efficacy data."

A clinical trial's DSMB is an independent group that reviews the data and makes recommendations to the clinical trial's sponsor about whether to continue the study, stop it early because of positive data, or stop it early due to futility or safety issues. By using an intermediary, the sponsoring company can remain blinded to the data as the clinical trial continues.

Gloved hands giving an injection into someone's shoulder.

Image source: Getty Images.

Following NIAID's announcement, AstraZeneca noted that the results disclosed on Monday were from a pre-specified interim analysis of data that was cut off as of Feb. 17. The data showed the vaccine had 79% efficacy at preventing symptomatic COVID-19 and 100% efficacy at preventing severe disease and hospitalization.

But more people in the clinical trial have come down with COVID-19 over the last month, resulting in enough cases that the company can now perform the pre-specified analysis on the full data set. AstraZeneca noted that the results were "consistent with the interim analysis" and says it plans to talk to the DSMB and issue results of the primary analysis within 48 hours of Tuesday's press release.

Investors will have to wait a little while longer to see if the final results will end this drama once and for all.

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