What is going on with the results from the United States AstraZeneca trial?


A: Despite a *strange* communication week, the new trial results show that the Oxford/Astrazeneca is safe and effective. GOOD NEWS!

TL:DR: AstraZeneca’s first results this week were based on data collected in the U.S. through a pre-specified end date for interim analysis of February 17th. They continued to collect data beyond that date and have now released updated efficacy results…spoiler alert….they are very similar (76% vs 79%).

On Monday March 22nd, AstraZeneca reported results (by press release) but received push-back on March 23rd from the U.S. Data Safety and Monitoring Board who claimed the press release efficacy was not based on full data. AstraZeneca explained that February 17th was a pre-specified date that had been set for interim analysis and that they would release results based on data collected across the entire study within 48 hours.

Overall, it seems like this can be chalked up to an unfortunate communication SNAFU regarding what AstraZeneca was actually reporting out on Monday—definitely a major drawback of “science by press release.”

Today, AstraZeneca reported updated results based on the full range of data collected (via another press release).

Results for the dosing strategy of 2 doses administered 4 weeks apart, events counted starting 15 days after 2nd dose:

➡️ 190 symptomatic cases of COVID-19 occurring among 32,449 trial participants (previously 141 cases were reported)
➡️ Overall efficacy (symptomatic disease) was 76% (previously reported to be 79%)
➡️ Efficacy in people aged 65+ years was 85% (previously reported as 80%)
➡️ NO cases of severe or critical disease or hospitalization in the vaccine group (same as previously reported)


Another vaccine that is highly effective against COVID-19 disease is on the horizon in the U.S. Emergency use authorization is expected to be requested by AstraZeneca soon.
Notably, millions of Astrazeneca doses have already been deployed globally, for example in the UK, Europe, and India.

Once the full study is published, we will take a deeper dive into the detailed results—stay tuned for more Nerdy updates!!

Those Nerdy Girls

Further Reading:



AP News

First press release by AstraZeneca

AstraZeneca’s second press release

Today’s AstraZeneca press release

Efficacy Table from Dr. Eric Topol

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