U.S. CDC testing guidance was published against scientists' objections

Commenting on contradictory remarks by the U.S. president and health officials, the World Health Organization's top emergency expert, Mike Ryan, said it is important for all states to have "consistent messaging" for their public.

Redfield, masked at times in a Senate hearing room, also spoke emphatically of the importance of everyone wearing protective masks to stop the pandemic, which has killed almost 200,000 Americans. Dr. Redfield told a congressional hearing that health care workers, first responders, and others at high risk would get the vaccine first, perhaps in January or even late this year, but it was unlikely to be available more broadly, again assuming approval, before late spring or summer of 2021.

Trump also disagreed with Dr. Robert Redfield about the effectiveness of protective masks - which the president recommends but nearly never wears - and said he would telephoned Redfield to tell him so. "I think he got the message maybe confused, maybe it was stated incorrectly".

A potential vaccine for COVID-19 - and how it will be evaluated and distributed when it's ready - has taken center stage in the presidential race with seven weeks to go until the November election. "But once we go, we're ready", Trump said.

The head of the Centers for Disease Control and Prevention warned Wednesday that US residents shouldn't expect to receive a vaccine for the coronavirus until at least mid-2021, contradicting President Trump's claim that at least 100 million doses could be distributed by the end of 2020.

Despite quibbling with Redfield, Trump said he retained confidence in his performance at the CDC.

Later Wednesday, Redfield took to Twitter with a few lasting thoughts.

When will we have a COVID-19 vaccine? "The best defense we now have against this virus are the important mitigation efforts of wearing a mask, washing your hands, social distancing and being careful about crowds".

"That was a doc that came from the top down, from the H.H.S. and the task force", said a federal official with knowledge of the matter, referring to the White House task force on the coronavirus.

At a Senate subcommittee hearing on Wednesday, CDC Director Robert Redfield said most Americans probably wouldn't receive a coronavirus vaccine until "late second quarter, third quarter 2021".

"It's not more effective by any means than a vaccine and I called him about that, those were the two things I discussed with him", Trump said in response, according to The Hill.

Trump made the prediction even though the vaccine is still being tested in human subjects, and some health experts have said they believe a safe and highly effective vaccine is several months way, if not much longer.

It's not the Trump administration's first rodeo with going against the guidance from its own team that specializes in infectious diseases.

The New York Times now reports that recommendation "was not written by C.D.C. scientists and was posted to the agency's website despite their serious objections". She's an alumna of Boston University and has reported for the Wall Street Journal, Science, and The Boston Globe.

Katie Camero is a McClatchy National Real-Time reporter based in Miami focusing on science.