AstraZeneca's COVID-19 vaccine. Dado Ruvic/Reuters In the UK, vaccines Pfizer, Moderna, and AstraZeneca are being used to fight the pandemic. AstraZeneca's hasn't been approved for use yet in the US. AstraZeneca may not apply for a US FDA Emergency Use Authorization until the spring. The data from their UK trial was "odd" and had one "pretty serious error" in it, a US vaccine expert said.