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Coping with COVID: Final trials show AstraZeneca COVID-19 vaccine safe with 70 percent efficacy

Across 11,000 participants of the AstraZeneca COVID-19 vaccine, results showed a 70 percent effective rate in recent late-stage trials. Although trials continue, one standing concern of the vaccine is its lower level of efficacy compared to other candidates.

AstraZeneca’s COVID-19 vaccine was 70 percent effective at preventing infection from the virus in more than 11,000 participants in late-stage international trials, according to results published Dec. 8 in The Lancet. 

The vaccine was only about 60 percent effective among people who received the standard two-dose regimen, but was 90 percent effective in those who received a half-dose the first round and a full dose the second round. About 2,700 volunteers were accidentally given a half-dose for their first shot and a full dose the second time. It’s unclear if their better efficacy rate was a statistical fluke or if the lower dose prepped the immune system to be better protected, USA Today reported. 

AstraZeneca and its partner Oxford University said they need more data from the trials to figure out if the half-dose, full-dose regimen is actually more effective. 

AstraZeneca said the trial results were strong enough to apply for authorization from the U.K., European Union and elsewhere, but the U.S. will likely wait for results of a larger, 30,000 person trial being conducted in the U.S. to make a regulatory decision. Those results will likely come early next year, USA Today reported.