Sean Penn is firm in his stance on COVID-19 vaccines: Will Hollywood stand with him?

Get the jab or stay home.

That's the feeling of actor/activist Sean Penn, who firmly believes that film studios and production companies should require everyone to be vaccinated before walking onto the set.

"I think it should be as mandatory as turning on your headlights on a car at night," Penn says bluntly, talking to USA TODAY late last month. The Oscar winner, who directs and co-stars in "Flag Day" (in theaters now) with daughter Dylan Penn, made headlines in July for refusing to shoot his new Starz series "Gaslit" until all cast and crew members were vaccinated.

"I will go back to work on 'Gaslit' when it has been confirmed to me that the entire crew, top to bottom, will be vaccinated," Penn tells USA TODAY. That extends to moviegoers who might see "Flag Day," too: "I don't want people that are unvaccinated to go to theaters to see this or any other movie."

Dylan Penn, left, and father Sean Penn during a news conference for "Flag Day" at Cannes Film Festival.
Dylan Penn, left, and father Sean Penn during a news conference for "Flag Day" at Cannes Film Festival.

Penn is one of many stars who have taken a stance in favor of vaccines. Celebrities including Jane Fonda, Samuel L. Jackson and Ryan Reynolds have shared photos of themselves getting the shot. "I fall heavily on the side of trusting science more than something you read on Facebook," Matt Damon told Yahoo Entertainment in July while promoting "Stillwater." Jennifer Aniston, meanwhile, drew mixed reactions on social media last month after telling InStyle that she cut "a few people" out of her inner circle because they were unvaccinated.

Then there's Tom Cruise, who went viral last December for his expletive-laden rant against crew members who broke COVID-19 safety protocols on the set of "Mission: Impossible 7." Production on the action film has been delayed at least six times because of the pandemic, according to Variety. Paramount purchased a $100 million insurance policy for the movie but was only reimbursed $5 million for COVID-19 losses, leading the studio to sue Federal Insurance Co. last month, according to Bloomberg. (Paramount declined USA TODAY's request for comment on its vaccine policies.)

With costly production shutdowns, and cases of delta and other variants spiking around the country, it's only a matter of time until major studios start taking stricter measures, experts say.

"We're definitely moving in the direction of mandatory vaccines across the industry," says Sebastian Hayto, chief operating officer of Kameo, a leading COVID-19 testing provider for film and TV productions. "As major institutions, major studios and even major corporations look at Facebook and Twitter and all these other companies that are really setting the stage for what return to work needs to look like – let alone the statewide regulations that are going into place – I think it's becoming a lot more commonplace for vaccines to be mandated."

In July, Netflix announced that it will require all actors and "Zone A" crew members – those who come into close contact with the actors – to be vaccinated. Vaccine mandates don't apply to people in Zone B, which includes production offices, control rooms and vehicles on sets, or Zone C, which encompasses hotels, homes and other places off-site where employees may go when they're not working. But varying levels of COVID-19 testing, masks and social distancing still apply to all three zones.

"Netflix is leading the charge and all eyes are on them with regards to their vaccine mandates," says Hayto, who is aware of some other sets that require 100% vaccination. "Especially for smaller studios and two-day commercial shoots, it's just a nonstarter that you must be vaccinated."

According to the Screen Actors Guild – American Federation of Television and Radio Artists, Hollywood's biggest union, producers are legally allowed to implement a mandatory vaccination policy, so long as they follow parameters set out in the Return to Work Agreement.

Kameo provides COVID-19 tests to film and TV productions.
Kameo provides COVID-19 tests to film and TV productions.

Other areas of the entertainment industry are adjusting mandates as well. Later this month, the Emmy Awards will require all attendees to show negative COVID-19 tests in addition to proof of vaccination. This month's Toronto International Film Festival is also ordering festivalgoers to show proof of a negative test or vaccination to attend.

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"Hollywood can get back to more a semblance of normal if we can ensure that a maximum proportion of our audience is vaccinated, and those who are not, demonstrate they are not a menace to others," says Sten Vermund, dean at the Yale University School of Public Health. "That's going to be your anchor and your backbone for festivals, awards shows and production."

But mandating vaccines may not be enough. In an opinion piece for The Hollywood Reporter in June, "Criminal Minds" actress Shira Scott Astrof said she "was shocked at how many" of her Hollywood peers are skeptical of the vaccines. Actors including Rob Schneider ("Grown Ups") and Letitia Wright ("Black Panther") have gotten backlash for sharing vaccine misinformation on Twitter, while Carrie Underwood drew ire online last month for "liking" an anti-mask tweet.

Hollywood is trying to flip the script. With just 53.3% of the U.S. population fully vaccinated, according to the Centers for Disease Control and Prevention, Hollywood, Health & Society is working with TV creatives to incorporate better education about COVID-19 symptoms, testing and vaccines into storylines on their shows. Hollywood, Health & Society is a program of the University of Southern California's Annenberg Norman Lear Center.

“We know from our research that the effect TV storylines have on audiences is profound," says program director Kate Langrall Folb. "Popular TV shows have helped audiences learn about HIV/AIDS, cancer, addiction, mental health and much more. We’ve worked with over a dozen shows this year on COVID-19 storylines so far, and some, like 'Grey’s Anatomy' and 'New Amsterdam,' have already addressed the vaccine. It is our hope that TV writers will continue to embrace accurate COVID-19 storylines based in science to help audiences make informed decisions for their own health.”

Kristen Stewart holds her face mask as she attends a photocall for the film "Spencer" at Venice Film Festival.
Kristen Stewart holds her face mask as she attends a photocall for the film "Spencer" at Venice Film Festival.

And with many people around the country still resisting masks, global event designer Edward Perotti, who has thrown parties for Ariana Grande and Nick Jonas, believes that more celebrities should be leading by example. Stars such as Kristen Dunst and Penelope Cruz masked up at this month's Venice Film Festival, which requires proof of vaccination or a negative test, but many others have been pictured without.

"Would I expect to see an A-lister whip out their (vaccination) card out of their bag on the red carpet? Absolutely not," Perotti says. "But wouldn't it be nice to see them walk the red carpet, take their mask off and then put it back on again? Just those little things would make all the difference."

This article originally appeared on USA TODAY: Why Hollywood is 'definitely' moving toward requiring COVID vaccine