Just before she received her second Pfizer vaccine on April 2, Bella Sabino said she couldn't scroll through TikTok without seeing a slew of videos declaring Pfizer the "hot vaccine."
"People were making it into a really fun joke ... you know, Johnson and Johnson versus Pfizer versus Moderna," said Sabino, 19, who attends Fordham University in New York.
So, after getting fully vaccinated, Sabino lip-synced the audio she had heard over and over again, the one that had decreed those who got Pfizer "hot," while lifting her sleeve to reveal the band-aid where she'd gotten her shot.
"Um, only hot people get the Pfizer vaccine," the popular audio, recorded by TikTok user "idrinkurmilkshake" announces. "If you got Moderna then, I don't know what to tell you, queen. This message is brought to you by Pfizer gang."
Like millennials and Gen Xers posting "vaccine selfies" on Twitter before them, more young people are seizing the moment to create vaccine-centric trends on TikTok as they become eligible to be vaccinated. Among the first such trends is vaccine rivalries.
Like the "Pfizer gang," those with Moderna declare themselves superior because country singer Dolly Parton donated $1 million toward its creation. Many joked that the Johnson & Johnson vaccine was the "Walmart vaccine" because its efficacy was lower than that of Pfizer or Moderna, according to the U.S. Centers for Disease Control and Prevention.
"Everybody loves a little rivalry whether it's sports or something like that. It definitely brings the commotion and makes people excited," said Lena Daniels, 22, of Orlando, Florida, who got her first Pfizer vaccine on April 6.
The CDC reported that of the people in the United States who have received at least one dose of the Covid-19 vaccine, approximately 9.5 percent of them were 18 to 29.
Daniels said most people she knows who are her age are excited to get vaccinated, and the rivalries on TikTok are an expression of that excitement.
"Most people my age are very progressive in their thought process and they're just excited to get their lives back, and being so close to summer everyone is so excited to start traveling and get their lives back on track," she said.
Daniels also posted a video set to the audio about Pfizer being for "hot people," while showing off the Band-Aid on her arm. She said her comments have been filled with people joking that TikTok's algorithm had gotten scary specific by showing them Daniels' video right after they, too, received a Pfizer vaccine.
"Some of the comments are like, 'How did everyone know I got Pfizer? All my TikToks are about Pfizer.' And just a nod to TikTok's algorithm knowing everything about us, honestly," Daniels said.
Some have used the vaccine and vaccine rivalries as a way to both show off that they've been vaccinated but also to assuage fears that their loved ones might have that the vaccine will make them sick.
"I kind of wanted to brag humbly about how I was getting vaccinated so I did that to show my friends and my family — my family is a little skeptical about the vaccine — I wanted to show them that it's totally fine," said Tiffany Selberg, 20, of North Carolina, who is scheduled for her second shot of Moderna on Monday, April 12. "It's kind of something a lot of people in Gen Z are using to unite and fight against the virus."
In March, after her first dose, Selberg posted a video to TikTok of herself showing off her vaccine card with a caption that reads, "MODERNA GANG RISE UP."
Although it doesn't appear the vaccine rivalries are being used to spread misinformation about the vaccine, TikTok provides a banner on videos discussing Covid-19 vaccines that can link viewers to an in-app coronavirus resource hub with commonly asked questions and answers about Covid-19 vaccines. The answers to the questions come from the CDC and the World Health Organization.
But not all the rivalries are meant to be about which vaccine is superior. Some have likened the three vaccines to the three factions in the game Pokemon Go and the Hogwarts houses from the Harry Potter series.
Those who spoke to NBC News said they predict that the rivalries are the first of many vaccine-related trends TikTok will see in the coming months, adding that they believe it reflects the excitement and eagerness young people feel about getting back to normal life.
"We all have a lot of hope for the future now that everyone is being vaccinated, so all of the conversations, as silly as they are, everyone is just really happy that we're at this point in time," Sabino said.