National Institute of Allergy and Infectious Diseases (NIAID) Director Anthony Fauci's often inconsistent comments and mixed messages on the coronavirus pandemic are prompting renewed scrutiny as debate rages over reopening schools and businesses nearly a year after the lockdowns started.

"Dr. Fauci is a very good public-health official. His job is to advise policy makers and inform the public," Sen. Marco Rubio, R-Fla., said on Tuesday. "But his job is NOT to decide what we can do, where we can go or which places can open or close And his job is NOT to mislead or scare us into doing the 'right things.'"

"Why should we trust Fauci with a national plan? Back in March, Fauci famously told Americans, 'There’s no reason to be walking around with a mask,'" wrote David Harsanyi in the National Review. "(Fauci now says we should wear two masks. No thanks, Dad.)"

Masks

Fauci in an interview on "60 Minutes" in early March of last year warned of "unintended consequences" of masks, saying "people keep fiddling with the mask and they keep touching their face." 

In this Dec. 22, 2020, file photo, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks before receiving his first dose of the COVID-19 vaccine at the National Institutes of Health, in Bethesda, Md. (AP Photo/Patrick Semansky, Pool, File)

DR. FAUCI: IT'S 'POSSIBLE' AMERICANS MAY STILL BE WEARING FACE MASKS IN 2022

On masks, Fauci and former Surgeon General Jerome Adams – who also warned against buying and wearing masks in spring 2020 – said officials recommended against wearing masks early in the pandemic because at the time there was a massive shortage of PPE for medical workers who needed it most. Further, more evidence of asymptomatic spread of the virus later came out. 

Fauci later enthusiatically embraced wearing masks.

"What has changed in our recommendation?" Adams said in a White House briefing in July. "We now know from recent studies that a significant portion of individuals with coronavirus lack symptoms."

Now, Fauci more recently has backed recommendations that Americans wear two masks instead of one if possible in order to keep the masks tighter on people's faces. 

"If you have a physical covering with one layer, you put another layer on it just makes common sense that it likely would be more effective," Fauci told NBC News last month. The CDC officially put out double-masking guidelines this month. 

FAUCI BACKS 'DOUBLE-MASKING' IN CORONAVIRUS FIGHT, SAYS 'LIKELY MORE EFFECTIVE'

Vaccinations

Another issue on which Fauci has adjusted his stances is on exactly what level of vaccination is necessary for the U.S. to reach herd immunity to the virus. Fauci previously said the percentage of Americans who need to be vaccinated to reach that goal was 70% before revising that number up to higher than 80%. 

This inspired a story in the New York Times that accused Fauci of "quietly shifting" recommendations. Fauci then explained to the paper that he was taking public opinion polls into account in how he shaped his comments. 

"When polls said only about half of all Americans would take a vaccine, I was saying herd immunity would take 70 to 75%," Fauci said, according to the paper. "Then, when newer surveys said 60% or more would take it, I thought, ‘I can nudge this up a bit,’ so I went to 80, 85."

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, waits to testify at a hearing of the U.S. House Committee on Energy and Commerce on Capitol Hill on June 23, 2020 in Washington, DC. (Photo by Kevin Dietsch-Pool/Getty Images)

He continued: "We have to have some humility here ... We really don’t know what the real number is. I think the real range is somewhere between 70 to 90%. But, I’m not going to say 90%."

And on returning to normal after Americans get their vaccines, Fauci has made several different comments that are not necessarily consistent. 

DR. FAUCI: US WILL HAVE 600M CORONAVIRUS VACCINE DOSES BY JULY 2021

"It's gonna depend very much on what the percent or level of efficacy of the vaccine is," Fauci said in an interview of what post-vaccine life would look like with Bloomberg in August. "I would be very happy with 70-75% and I would be accepting of 50 to 60%."

Fauci said continued public health measures would be necessary if the vaccine was on the low-end of effectiveness. But vaccines have been shown to be significantly more effective than anticipated – upwards of 90% – and Fauci now says Americans may need to wear masks until 2022. 

"Obviously, with a 90-plus-percent effective vaccine, you could feel much more confident," Fauci said on CNN in November. "But I would recommend to people to not abandon all public health measures just because you have been vaccinated, because even though, for the general population, it might be 90 to 95% effective, you don't necessarily know, for you, how effective it is."

He added Sunday, also on CNN, that whether Americans wear masks into 2022 "depends on the level of dynamics of the virus that's in the community... If you see the level coming down really, really very low, I want it to keep going down to a baseline that's so low, that there's virtually no threat – or not no. It'll never be zero, but a minimal, minimal threat that you will be exposed to someone who is infected."

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks about the coronavirus in the James Brady Briefing Room last week. A Long Island, N.Y. restaurant has named a dish after Fauci. (AP Photo/Alex Brandon)

FAUCI CAUTIONS AGAINST DINING OUT, EVEN WHEN VACCINATED

More than 500,000 Americans have died from the coronavirus, which is an airborne disease that is not severe in most healthy people but can be deadly to older people and those with compromised immune systems. Fauci and his defenders have said their recommendations on the virus, which did not exist before 2019, have evolved as Americans' understanding of the virus has evolved. They also say the strict recommendations reflect the vast number of deaths the virus is capable of causing and has caused. 

But those who are more critical of Fauci say he made pronouncements of "science" with far too much finality when the science was not in fact settled; has not leveled with Americans in some cases, including on the length of the lockdowns; and is not taking into account the mental and emotional toll of the virus lockdowns. 

Also this month, Fauci said on NBC's "Today" that "by the time we get to April, that would be what I would call ... open season" on vaccines and nearly full vaccination by "the middle and end of the summer." The epidemiologist was then contradicted by President Biden, who said in a CNN town hall that vaccine would be available to all Americans by the end of July, and it would take longer than that to get doses in everybody's arms. 

Fox News reached out to the NIAID for comment on Fauci's messaging on masks, herd immunity, vaccines and when life may return to normal and did not receive a response. 

Lockdowns

Many Americans continue to wonder when the nation's top infectious disease expert will tell them that they can resume life as normal.

One issue on which Fauci has remained more consistent is the reopening schools, which he has reiterated is possible before teachers get vaccines. In fact, he said this month on CBS that vaccinating every teacher before opening schools is "non-workable."

President Joe Biden speaks during the 59th Presidential Inauguration at the U.S. Capitol in Washington, Wednesday, Jan. 20, 2021.(AP Photo/Patrick Semansky, Pool)

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Fauci on Sunday declined to say on CNN that grandparents who are fully vaccinated could see their grandchildren, saying "I don't want to be making a recommendation now on public TV. I would want to sit down with the team, take a look at that."

That prompted a rant from Meghan McCain on "The View." 

"I was very frustrated when I saw this clip," she said. "The fact that Dr. Fauci is going on CNN and he can’t tell me if I get the vaccine, I’ll be able to have dinner with my family... It’s terribly inconsistent messaging and it continues to be inconsistent messaging."

Fauci answered some of that criticism on CNN Tuesday. 

"If I'm fully vaccinated and my daughter comes in the house and she's fully vaccinated ... common sense tells you that in fact you don't have to be as stringent," Fauci said. But, he added, "we want to get firm recommendations from the CDC" on what people can and cannot do when they are vaccinated. 

Fox News' Kayla Rivas contributed to this report.