AstraZeneca reports efficacy in interim analysis of COVID-19 vaccine

Nov. 23, 2020

AstraZeneca announced that positive high-level results from an interim analysis of clinical trials of AZD1222 in the UK and Brazil showed the vaccine was effective in preventing COVID-19.

The experimental vaccine has achieved an average of 70% efficacy in a late-phase analysis. Two different dosing regimens demonstrated efficacy with one showing a better profile.

One dosing regimen showed vaccine efficacy of 90% when AZD1222 was given as a half dose, followed by a full dose at least one month apart, and another dosing regimen showed 62% efficacy when given as two full doses at least one month apart. The combined analysis from both dosing regimens resulted in an average efficacy of 70%.

In an interview with CNBC, Dr. Ruud Dobber, President of AstraZeneca US, commented on the low dose/high dose versus high dose/high dose effectiveness. "It's a little bit too early, but one of the potential hypotheses is that you're priming the immune system with a relatively low dose or lower dose as a consequence, the immune system is firing against this virus. But equally, I also need to admit that it was a little bit of a surprise to all of us in order to see this difference. We really expected to have a high dose/high dose very effective. It's very effective, but the half dose/full dose, clearly has a better efficacy, and we will do more research in the weeks to come in order to better understand the mechanism here," said Dobber.

The pooled analysis included data from the COV002 Phase II/III trial in the UK and COV003 Phase III trial in Brazil.

AstraZeneca is the third drugmaker to demonstrate late-stage vaccine efficacy,  with the Pfizer-BioNTech and Moderna vaccines both reporting efficacy of over 90% earlier this month.

According to AstraZeneca, they will now immediately prepare regulatory submission of the data to authorities around the world that have a framework in place for conditional or early approval. The drugmaker will seek an Emergency Use Listing from the World Health Organization for an accelerated pathway to vaccine availability in low-income countries. In parallel, the full analysis of the interim results is being submitted for publication in a peer-reviewed journal.

Read the press release