Director of the Centers for Disease Control and Prevention (CDC) Dr Robert Redfield claimed that masks offer more certain protection against coronavirus than vaccines will - at least in the immediate future.
'I might say this face mask is more guaranteed to protect me against covid than when I take a vaccine' said Dr Redfield during his Wednesday testimony before a Senate subcommittee.
He pointed out that there is more research to clearly show that masks work to block the spread of infectious particles, while vaccines are still in testing and their true efficacy won't be entirely clear until large groups of people have been dosed.
Dr Redfield's comments came as part of the same testimony in which he and other officials presented a plan to give all Americans free coronavirus vaccines, distributing them to the general public as January.
CDC Director Dr Robert Redfield on Wednesday said that masks offer more 'guaranteed' protection against coronavirus than prospective vaccines, because there is more scientific proof they work than as-of-yet unproven shots
But the CDC head walked back the optimism of the 'playbook' and Trump himself, estimating that vaccines won't be broadly available to Americans until spring or summer of next year.
Trump continues to insist that a vaccine is only 'weeks' away while hinting at his hope that the Food and Drug Administration (FDA) will approve one ahead of the November 3 election.
The CDC director's apparent endorsement of masks and sobering view of vaccines was typical of his tense day before the Senate on Wednesday.
While trying to temper expectations set by the 'playbook' for distributing coronavirus vaccines published by his agency in conjunction with other health agencies and the Department of Defense, Dr Redfield also had to bat back criticism.
The CDC's game plan assumes that tens of millions of doses of a vaccine will be available to send freely to Americans - not just frontline workers - by January 2021.
In turn, that assumes approval of a shot by the end of next month.
Health experts, including Dr Redfield, have said that that is possible, but not likely.
Senator Jeff Merkley, a Democrat