US infectious disease official Anthony Fauci said AstraZeneca's Covid-19 vaccine had good efficacy, but safety concerns needed to be straightened out and it might not be needed for Americans because of supplies of other shots.

"I think that the AstraZeneca vaccine from a standpoint of efficacy is a good vaccine, and if the safety issue gets straightened out in the European Union... the efficacy of that vaccine is really quite good," he told BBC radio on Tuesday.

"Whether or not we ever use AZ is unclear but it looks right now at this point in time that we will not need it. It's not a negative indictment of AZ, it is just possible that given...