Interim clinical trial results that include data from local volunteers show the Oxford-AstraZeneca COVID-19 vaccine candidate is 100 percent effective in preventing hospitalizations and death.
Final analysis from the U.S. Phase III clinical trial is expected in a few weeks, after which AstraZeneca is expected to apply for emergency use authorization from the Food and Drug Administration.
More than 32,000 volunteers at 88 sites across the country took part in the trial. Local volunteers—more than 850 people—participated at the University of Rochester Medical Center site, which joined the study last July.
“It’s gratifying to see how well this vaccine was tolerated and how well it protected people from severe disease,” says Ann Falsey M.D., co-lead principal investigator of the U.S. clinical trial and co-director of the URMC Vaccine and Treatment Evaluation Unit. “After working on the frontlines last March, to see none of AstraZeneca-vaccinated participants in this trial ending up in the hospital with COVID is a huge relief. It is amazing how well this vaccine works.”
Known as AZD1222, the vaccine was co-invented by the University of Oxford and its spinoff, Vaccitech. According to AstraZeneca, it uses a replication-deficient chimpanzee viral vector based on a weakened version of a common cold virus that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein. After vaccination, the surface spike protein is produced, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body.
The vaccine is 79 percent effective at preventing milder infections. [An updated analysis that AstraZeneca released on Wednesday showed a slightly lower but still robust rate of effectiveness: 76 percent.] The U.S. trial showed no safety concerns of any kind related to the vaccine including risk of blood clotting, URMC says. Locally, the study was led by Falsey; Angela Branche M.D., who co-directs the URMC Vaccine and Treatment Evaluation Unit; and Michael Keefer M.D., who is in charge of the URMC HIV Vaccine Trials Unit.
Roughly 79 percent of participants in the interim analysis were white; 8 percent were African American; 4 percent were Native American and 4 percent were Asian. Twenty-two percent of participants were Hispanic, AstraZeneca says. Roughly 60 percent of the volunteers had co-morbidities associated with an increased risk for progression of severe COVID-19, such as diabetes, severe obesity or cardiac disease.
The trial used two vaccine doses at a four-week interval. The vaccine can be stored, transported and handled at normal refrigerated conditions for at least six months, and administered without the need for preparation.
Though some batches of the vaccine were stopped in Europe, the European Medicines Agency upheld its decision to continue with vaccinations after studying evidence of the rare events that were linked to the AZD-1222 vaccine. The EMA committee concluded that the vaccine is not linked with the risk of blood clots in those who receive it. However, the vaccine might be associated with rare cases of blood clots tied to low levels of blood platelets.
The U.S. independent data safety monitoring board did not identify safety concerns related to the vaccine. It did not find an increased risk of clotting among participants who received at least one dose of the vaccine, AstraZeneca says.
“As nations around the world struggle to vaccinate their populations, these results are great news,” Branche says. “More analysis and review is needed, but I am hopeful that this vaccine will soon be added to the existing arsenal of safe, approved COVID vaccines.”
Smriti Jacob is Rochester Beacon managing editor.