Pfizer, founded in 1849, is one of the biggest pharmaceutical companies on Earth; it’s used to major announcements like this. The year before the pandemic, Pfizer employed about 88,300 people around the globe.

But before the pandemic, Moderna, a biotech company based in Cambridge, Mass., was not used to the big headlines. It was founded in 2010 and employed just 700 people in early 2020. Pfizer has a $300.9 billion market cap; Moderna’s is $72 billion.

Moderna was able to rise to the challenges of the pandemic because of the company culture, says Tracey Franklin, the company’s chief human resources officer. Each person, whether they’re developing the mRNA that ultimately ended up saving an untold number of lives, or they’re processing company payroll, felt connected by the spirit of the work they were doing. 

But how did Moderna balance its all-important lab work during the pandemic with preventing burnout in its ranks? It starts with intelligent hiring, Franklin says. And she revealed the secrets of the company culture that helped the millennial-heavy company stave off burnout while developing one of the most important vaccines ever. It all comes down to the right “mindsets,” she says.

‘We essentially had to build the company overnight’

Franklin was fairly new to the company when everything changed, having started at Moderna in September 2019.  “We essentially had to build the company overnight,” she tells Fortune. Prior to the pandemic, Moderna was made up of 700 or so “early-stage biotech people,” she says. “We had to build out a whole arm of the company that hadn’t existed before, cross-functionally, globally, in all different parts of the world. That rapid scaling is pretty unprecedented.”

Since the pandemic began, the company has grown nearly 330%, to about 3,000 people. To manage the constant influx of new talent, and ensure their needs are met, Franklin says the solution is twofold: on one hand, Moderna stresses a particular way that employees tackle their jobs, but on the other, it works hard to stay in tune with what employees say they want.

The first part of this solution comes back to what the company calls the 12 “Moderna Mindsets”: a set of tools that codify what’s unique to Moderna’s culture and that has guided decision making since the beginning. 

The list hits on a variety of abstract goals, beginning with “we act with urgency,” followed by “we accept risk,” “we pivot fearlessly,” and “we push past possible.” It can be difficult to distill the attitude of an entire corporation into 12, but Franklin says every decision at Moderna, top to bottom, is guided by the mindsets. They also serve as a clarifying set of principles for its windfall of new hires to really grasp what company leadership cares about. 

But while it has put these “Mindsets” in place, Franklin says she and her team engaged with each worker; she relies on a group called “voice of the employee” that gives the executive team constant feedback. Moderna’s talent and retention philosophy is principally about personalization. “We try not to have big blanket programs, but rather umbrella programs employees can personalize,” she says. “Whether it’s how your benefits are delivered, or what your equity is, or what perks you need. That’s really helpful from a retention perspective.”

The vaccine race reminded each member of Moderna’s workforce just how significant their work was. “During vaccine development, it was all about external impacts,” she says. “It was about, ‘how can we get this to patients and people in need faster?’ Not about politics or hand-wringing.” 

As the researchers raced to develop a vaccine, Franklin’s team rushed to support its entire employee body with the support they said they needed. These included running pop-up daycare centers when normal daycares closed, providing employees access to wellness coaches, daily free lunch, she says, which workers said they valued. “We want to make the easy things easy.”

Skewing younger

Moderna’s employee base is younger than the industry standard, with an average age of 37.  “At Moderna, a lot of what you’d call earlier career folks have gotten massive job opportunities,” she says. “It’s not about years of experience here; it’s about the ability to contribute, learn and have impact. That’s what we’ve prioritized.”

As Franklin has helped Moderna scale during the pandemic, she’s been working to hire the right leaders and nail down the right organizational structure to support its big launches. That has meant “totally rethinking HR in general.” The way she has operated in the past as a longtime HR executive might not be right anymore, she says.

“I balance my time between how we do HR at Moderna now, and how we should be doing it for younger people in the future,” she says.

To that end, she’s been working with Harvard MBA students to understand what, the best next version of employment looks like to them. She’s also worked with Harvard Medical School students to ask how Moderna can best appeal to the next generation, who it’s rushing to hire.

“We want the next generation of talent we’re hiring to influence how we do things,” she says. “This is a company that values accelerated career development. We’re trying to identify capability that can be fostered and nourished.”

Franklin goes back to the 12 Moderna Mindsets, which only date back to last summer. She says the company took a moment to reset and refocus after all the rapid growth, and spent some time developing the list.

“We had a whole bunch of people coming from different companies who were really thinking, ‘what a success at Moderna,’” Franklin recalls. “That’s how we created them. And you may think 12 is a lot, but this is what we value.”