A Last Of Us Fan Theory Links Ellie's Immunity To Her Biological Mother

Set 20 years after a brain-invading cordyceps outbreak decimated modern civilization, HBO’s The Last of Us doesn’t offer the survivors much hope. That is until an Infected bites a 14 year old named Ellie (Bella Ramsey), something that, under normal circumstances, would be an imminent death sentence. For some reason though, she never turns, seeming to indicate that Ellie is immune to the fungus. Believing that the teen has a “greater purpose,” Fireflies leader Marlene (Merle Dandridge) reveals to Ellie that whatever happened to her is the “key to finding the vaccine” that could save humanity and sends her on a dangerous cross-country expedition with smuggler Joel (Pedro Pascal).

So far, the TV adaptation hasn’t revealed much more about why Ellie is immune or how her blood might be used to cure those who contract the infection. The video game never offers concrete answers either because the Fireflies’ scientists are never able to experiment on Ellie. The reason? Joel finds out that the only way to reverse-engineer a vaccine is to extract the mutated cordyceps from Ellie’s brain through a surgery that would kill her in the process. Having grown attached to the teen, he rescues her from the lab to save her life.

However, the Naughty Dog game provides a hint about Ellie’s immunity if players are able to locate the surgeon’s recorder artifact. Noting that “the cause of her immunity is uncertain,” the doctor described her infection as something he’d never seen. “We're about to hit a milestone in human history equal to the discovery of penicillin,” he said. “After years of wandering in circles, we're about to come home, make a difference, and bring the human race back into control of its own destiny.”

Even though the scientists were uncertain about the origin of Ellie’s immunity, an item in her backpack provides a major clue. Ellie’s biological mother, Anna, wrote her a letter when she was “not even a day old,” explaining that her life was “about to get cut a little short” and Marlene would look after her. Several fans on Reddit interpreted that letter to mean that Ellie’s mom was bitten but stayed alive long enough to deliver Ellie. “The hours Anna spent fighting off the infection were vital, and allowed her to pass something to her daughter,” one user wrote. “The placenta allows mothers to pass antibodies on to their children, while also blocking some diseases. Even though Anna couldn't fight the infection on her own, her body fought it long enough to produce some antibodies/anti-fungal properties. Those would be passed on to the baby. . . . Or to put it another way... Ellie was vaccinated.”

It seems the HBO series will be more explicit. “There was a story that I had written after the game came out—about Ellie’s mom, that was going to be realized in this one way, and then it just kind of fell apart so it was always just sitting on a shelf,” game creator Neil Druckmann recently told Newsweek, recalling how he shared the plot with series co-creator Craig Mazin. “I mentioned this story to him and his eyes went wide and he was like, ‘Oh, my god, that has to go into the show.’”

Indeed, The Last of Us trailer briefly shows a woman holding a newborn baby, and actor Ashley Johnson is credited as Anna Williams, aka Ellie’s mother. Whether or not that means the HBO adaptation is going to confirm theories about Ellie’s immunity, viewers can at least expect to meet the teen’s mom.