AstraZeneca COVID-19 Vaccine 76% Effective in Phase 3 Trial

AstraZeneca recently announced that its COVID-19 vaccine was 76 percent effective against the coronavirus and 100 percent effective at preventing severe disease and hospitalization in a Phase 3 trial. 

The Phase 3 trial of the vaccine, AZD1222, enrolled 32,449 participants across 88 trial centers in the US, Peru, and Chile. There were a total of 190 symptomatic cases of COVID-19 present in the trial and two doses of the vaccine were administered at a four-week interval. 

Notably, participants aged 65 years and older saw vaccine efficacy of 85 percent. Of these individuals, 60 percent had co-morbidities associated with an increased risk for progression of severe COVID-19, such as diabetes, severe obesity or cardiac disease. 

There were eight cases of severe COVID-19 observed in the primary analysis, all of which were in the placebo group. The independent data safety monitoring board (DSMB) also found no safety concerns related to AZD1222. 

These results confirm vaccine efficacy consistent with the pre-specified interim safety and efficacy analysis announced at the beginning of the week. The interim analysis results were based on 32,499 participants with 141 symptomatic cases of COVID-19. 

In the analysis, AZD122 had the same efficacy at preventing severe disease and hospitalization (100 percent), but was found to be 79 percent effective against the coronavirus and 80 percent effective against individuals 65 years of age or older.   

Additionally, after a specific review of thrombotic events and cerebral venous sinus thrombosis, DSMB found no increased risk of these events among the 21,583 participants who received at least one dose of the vaccine. 

Although the numbers slightly changed from the interim analysis, the growing body of evidence reconfirms results observed in both the interim and primary results across all adult populations, especially in individuals aged 65 and older.

“The primary analysis is consistent with our previously released interim analysis, and confirms that our COVID-19 vaccine is highly effective in adults, including those aged 65 years and over. We look forward to filing our regulatory submission for Emergency Use Authorization in the US and preparing for the rollout of millions of doses across America,” Mene Pangalos, executive vice president of BioPharmaceuticals research & development, said in the announcement.

Ann Falsey, professor of medicine at the University of Rochester School of Medicine and co-lead principal investigator of the trial also said that these results offer confidence that adults of all ages can benefit from protection against the virus. 

DSMB recently expressed concern to NIAID, BARDA, and AstraZeneca, stating that AstraZeneca may have included outdated information from the trial.

In turn, this may have provided an incomplete view of the efficacy data. NIAID “urged” AstraZeneca to work with the DSMB to review efficacy data and ensure the most accurate and up-to-date efficacy data be made available. 
But AstraZeneca stated that the numbers published were based on pre-specified interim analysis with a data cut-off of February 17. After reviewing preliminary assessment of the primary analysis, the company completed the validation of statistical analysis. 

There are 14 additional possible or probable cases to be adjudicated, so the total number of cases and the point estimate may fluctuate slightly, AstraZeneca explained. But the company will submit the primary analysis for peer-reviewed publication in the coming weeks.

Once the vaccine is granted emergency use authorization, AstraZeneca plans to submit these findings to FDA to boost the rollout of the vaccine to individuals across the US.