The AZD1222 vaccine against COVID-19 has an efficacy of 63.09% against symptomatic SARS-CoV-2 infection. Longer dose intervals within the 8 to 12 weeks range are associated with greater vaccine efficacy.

Whaat happens if you mix AstraZeneca and Pfizer COVID-19 vaccines?

Researchers studied mixing and matching Pfizer's vaccine with AstraZeneca's, which is made using similar technology as J&J's. There, too, researchers found that people who got an AstraZeneca shot followed by Pfizer four weeks later produced more antibodies than those who received two AstraZeneca shots.

Is AstraZeneca COVID-19 vaccine approved by the FDA?

The AstraZeneca vaccine is not authorized for use in the U.S., but FDA understands that these AstraZeneca lots, or vaccine made from the lots, will now be exported for use.