“If you have the chance, get the shot. It will save your life.”

It was the kind of pro-vaccine message that a TV viewer has grown accustomed to hearing from public health officials, pop stars or President Biden. But it was delivered on Monday morning by Steve Doocy, co-host of the strongly right-leaning morning talk show “Fox & Friends” on Fox News Channel.

During the past few months, as some of his Fox colleagues have cast doubt and uncertainty about the safety of the coronavirus vaccines, most notably prime-time star Tucker Carlson, Doocy has emerged as one of the network’s biggest advocates for vaccines.

Echoing comments made by Rochelle Walensky, director of the Centers for Disease Control and Prevention, Doocy told viewers on Monday that “99 percent of the people who have died have not been vaccinated. And so, what they’re trying to do is … make sure that all the people who have not been vaccinated get vaccinated.”

The host then went on to list some popular conspiracy theories about the vaccines — adding “none of that is true.” While acknowledging “there are some people who have a reason they cannot get vaccinated,” he said, “everybody else, if you have the chance, get the shot. It will save your life.”

In contrast, Fox News prime-time host Sean Hannity drew some praise Monday night when he implored viewers to “please take covid seriously.” But he stopped short of directly encouraging vaccination, as Doocy had done. “You make the decision, in conjunction with your doctor, research on your own, that is best for you,” Hannity said — before pivoting to an alarming segment about a woman who was paralyzed for a month after taking a mandatory vaccine in 2019.

Doocy on Monday received plaudits from frequent Fox critics for his more strenuous endorsement of vaccines.

“Thank you Steve Doocy for telling the truth,” wrote Rep. Ted Lieu (D-Calif.), a prominent liberal congressman. “Every other Fox host, and every Republican official, should follow Doocy’s lead,” wrote Bill Kristol, a former Fox News contributor.

Doocy’s stature at the network gives his comments additional heft. He has been with Fox News since it was founded in 1996 and has been one of the faces of the network, growing in prominence as “Fox & Friends” took on new relevance and national importance during the administration of Donald Trump. His son, Peter, is the network’s White House correspondent.

On May 10, Doocy told viewers he felt “a relief” when he got vaccinated and said unvaccinated Americans are “the ones who are in peril.”

Talking up the benefits of vaccination just over a week later, Doocy said, “You don’t have to wear a mask indoors, you don’t have to social distance as long as you’ve had the shot. So the message is: If you don’t want to wear a mask, indoors, around people, get the shot.” Later, he emphasized “the vaccine is what’s going to keep a lot of people alive.”

On Friday, noting the sudden increase in cases nationwide after months of decline, Doocy said, “We’re going the wrong way because there are a lot of people who have not yet gotten the shot.” When Fox personality Lawrence Jones argued that some people don’t see the point of getting vaccinated, Doocy retorted: “You won’t die. That’s a good reason.”

But Doocy’s pro-vaccine encouragement has run up against his longtime co-host Brian Kilmeade, who has bristled at the push to encourage Americans to get vaccinated, even as cases have spiked in recent days because of the delta variant of the virus.

“I’m not telling anyone to get it, or not get it,” Kilmeade said in May. When Doocy argued that unvaccinated people could infect other unvaccinated people, Kilmeade replied, with obvious frustration, “That’s their choice.” (Kilmeade, Doocy and co-host Ainsley Earhardt have all been vaccinated, they have said.)

On Monday, Doocy and Kilmeade argued about the effectiveness of the vaccines, particularly against the delta variant. After Doocy’s plea for viewers to get vaccinated, Kilmeade told them, “You make your own decision. It’s available to everyone. We’re not doctors. I’m not going to go there and give you other medical advice.”

Fox News representatives did not respond to a request for comment on Doocy’s pro-vaccine advocacy, but the network said earlier this year that it has hosted many “pandemic-related town halls … while extensively promoting the use of mask-wearing and vaccinations to our audience via public service announcements across all of our key platforms.” The network has mandated safety protocols for employees who work in its headquarters, and its corporate parent company has allowed employees who get vaccinated to bypass daily health screenings for in-office work, journalist Ryan Grim reported Monday on Hill.TV.

Jonathan Reiner, a professor of medicine at George Washington University School of Medicine and Health Sciences and a CNN contributor who has criticized Carlson’s rhetoric about vaccines, praised Doocy’s advocacy in the mornings. But, he said in an email, “The large primetime audience has been hearing an entirely different message about the importance of vaccines.”

In April, Carlson suggested on air that vaccinated people were being asked to still wear masks in certain circumstances because “maybe [the vaccine] doesn’t work and they’re simply not telling you that.” The following month, he relied on unverified, self-reported data and alleged “more people … have died after getting the shot in four months during a single vaccination campaign than from all other vaccines combined over more than a decade and a half” — a claim that did not take into account how the normal rate of natural and accidental death would compare. On his fellow prime-time host Laura Ingraham’s show last week, a guest told viewers that “there’s no reason right now, no clinical reason to go get vaccinated.”

“The more positive messages that go out, I think they do affect some people,” said William Schaffner, professor of infectious diseases at the Vanderbilt University School of Medicine. Discouraging vaccination, he said, “may really reinforce the inclinations of some people not to get vaccinated and have them rooted more firmly in their reluctance to get vaccinated.”

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