U.S. Trial Results for AstraZeneca Vaccine Likely in January

AstraZeneca’s (AZ) late-stage U.S. coronavirus vaccine trial is likely to have efficacy data in January that could be enough for the company to request Emergency Use Authorization (EUA), Operation Warp Speed’s chief adviser Moncef Slaoui said this week.

Though the efficacy data recently unveiled by AZ from its phase 3 UK/Brazil trial demonstrated positive and encouraging effectiveness rates for the vaccine, AZD1222, it also raised serious questions because the one-and-a-half dose regimen — reportedly first tested in the trial by accident — was found to be significantly more effective than the double-dose.

Specifically, the one-and-a-half dose regimen showed 90 percent efficacy, while the double-dose showed only 62 percent efficacy. AZ has been giving the double dose in the U.S. trials, according to ClinicalTrials.gov.

Adding more uncertainty, a leading Oxford University scientist reportedly claimed this week that the smaller dose regimen was actually given to UK/Brazil trial participants on purpose after discussion, which would conflict with AZ’s explanation. The university has not yet confirmed this, and AZ did not respond for comment.

The confusion around the apparent superiority of the smaller dose has led AZ to plan a new global trial of its vaccine although it’s unclear which dosage the company will use in that trial (DID, Nov. 30).

The UK/Brazil efficacy results may not be enough for the FDA, which will likely want to see the data from the ongoing U.S. trial to clear up any confusion about the vaccine’s effectiveness, Slaoui said.

“It’s not obvious or straightforward to come to a conclusion why there appears to have been substantially different efficacy outcomes. Frankly, unless there is a very clear explanation based on facts and data of what’s behind those two [efficacy rates], it’s very likely that that package will not be sufficient for an [EUA],” he said.

The Operation Warp Speed adviser said that AZ’s phase 3 U.S. trial “is progressing very well,” having enrolled approximately 15,000 subjects to date. He added that Johnson & Johnson’s late-stage vaccine trial will also likely have enough efficacy data in January to potentially file for an EUA.

While it’s not yet known which vaccine the FDA might approve this month (it is reviewing EUA submissions from Pfizer and Moderna), Slaoui said the government is confident it will be able to distribute enough vaccine doses to immunize 20 million people in the U.S. in December, followed by distributions equating to 30 million vaccinations in January and 50 million in February.

“At the end of February, we will have potentially immunized 100 million people, which is really more or less the size of the significant at-risk population: the elderly, the healthcare workers, the first-line workers, people with comorbidity,” he said.

The first COVID-19 vaccine received authorization in a Western nation this week, with Pfizer’s highly effective shot, BNT162b2, receiving emergency clearance from the UK. Britain expects to begin administering the vaccine to high-risk patients next week.

The Pfizer vaccine will be discussed by the FDA’s vaccine advisory committee on Dec. 10 and the Moderna vaccine will be discussed at a meeting of the committee on Dec. 17. If things go well, EUAs could be issued shortly after, followed by distribution starting in 24 hours (DID, Dec. 3). — James Miessler