AstraZeneca Says COVID Vaccine Effective, 'No Safety Concerns'

A vial with AstraZeneca's CCP virus vaccine in Berlin on March 16, 2021. (Hannibal Hanschke/Reuters)

AstraZeneca said its COVID-19 vaccine is safe and effective following an interim analysis of data from a U.S.-based Phase 3 trial involving more than 32,000 participants.

"The vaccine was well tolerated, and the independent data safety monitoring board (DSMB) identified no safety concerns related to the vaccine," the company said in a March 22 statement.

The company said that the U.S. Phase 3 trial of the vaccine showed that it's 79 percent effective at preventing symptomatic illness and 100 percent effective against severe or critical disease and hospitalization.

Last week, more than a dozen nations suspended the use of the AstraZeneca vaccine, called AZD1222, after a few dozen people who received the vaccine developed blood clots. The European Union’s drug regulatory agency subsequently carried out a review and concluded that, while it couldn't rule out a direct link to thrombotic events—or blood clotting—the benefits of using the vaccine outweigh the possible risks.

Medical workers prepare doses of Oxford/AstraZeneca's COVID-19 vaccine at a vaccination center in Antwerp, Belgium, on March 18, 2021. (Yves Herman/Reuters)

Following the announcement by the European Medicines Agency, countries including France, Germany, and Italy resumed their use of the shot on March 19, with senior politicians rolling up their sleeves in a bid to allay public concerns and show the vaccine was safe.

AstraZeneca said the safety monitoring board carried out "a specific review of thrombotic events, as well as cerebral venous sinus thrombosis (CVST) with the assistance of an independent neurologist" and found no increased risk of blood clotting among the 21,583 participants who received at least one dose of its vaccine.

German police officer Dirk Moeller gets an AstraZeneca vaccination against the CCP virus at a new vaccination center at the former Tempelhof airport in Berlin on March 8, 2021. (Tobias Schwarz/Pool via AP)

Dr. Paul Hunter, a professor of medicine at the University of East Anglia in the UK, told The Associated Press that the results were reassuring, but more details were needed to back up AstraZeneca's claim that the vaccine was fully effective at preventing severe disease and hospitalization.

”It would be good to know how many severe cases occurred in the control group and so what the confidence intervals are for this 100 percent figure," said Hunter, who wasn't connected with the study. “But this should add confidence that the vaccine is doing what it is most needed for.”

AstraZeneca's interim safety and efficacy analysis was based on 32,449 participants, with 141 symptomatic cases of COVID-19, the disease caused by the CCP virus. Two-thirds of the trial participants received the vaccine—two doses four weeks apart—while the rest got placebo shots.

Investigators said the vaccine worked across adults of all ages, including older people, with 80 percent efficacy in participants aged 65 years and over.

“These findings reconfirm previous results observed,” said Ann Falsey, of the University of Rochester School of Medicine, who helped lead the trial. “It’s exciting to see similar efficacy results in people over 65 for the first time.”

AstraZeneca said it would continue to analyze the U.S. data before submitting it to the Food and Drug Administration (FDA) and applying for emergency use authorization of its vaccine, according to Ruud Dobber, a company executive vice president.

Dobber told reporters on March 22 that if the FDA approves the vaccine, the company will deliver 30 million doses immediately—and another 20 million within the first month.