|A breakdown of the Pfizer vaccine and why most people will qualify for the injection
Most people won't experience allergic reactions to the vaccine, experts insist.
The Food and Drug Administration late Friday authorized Pfizer's COVID-19 vaccine for people ages 16 and up, but warned that those with known severe allergic reactions to any of the vaccine's components should avoid taking it.
But this begs the question -- what is in the vaccine?
The good news is that Pfizer's mRNA vaccine doesn't contain any known allergens like eggs or metals.
"There are no derivatives of food allergies, there is no aluminum or mercury or anything like that," Dr. David Stukus, director of the Food Allergy Treatment Center at Nationwide Children's Hospital, said in an interview with ABC. "There is nothing in there that is inherently allergenic."
In fact, to allergy experts, most of the ingredients don't raise any alarm bells. Pfizer's vaccine has genetic material known as mRNA, as well as fats, salts and other ingredients commonly found in everyday medications that help maintain stability.
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Because we already have mRNA in nearly every cell of our bodies naturally, it's harmless, experts explained. The lipids, or fat lobules, and salts found in the vaccine add stability and structure to the mRNA and also help the mRNA slide into our cells. This way, our immune system's cells can appropriately respond and learn to attack the virus when exposed to it naturally in the real world.
There is only one ingredient in the vaccine, called PEG, that could potentially cause an allergic reaction, but experts agree it is unlikely to be a problem for the vast majority of people.
PEG "is a very common inactive ingredient found in a lot of over-the-counter things and in a lot of injectable medications," Dr. Erin L. Reigh, a staff physician in the Section of Allergy and Clinical Immunology at Dartmouth-Hitchcock Medical Center, told ABC News.
"I have seen a few cases of allergies to this in my career, but it is very rare," she added.
In fact, PEG is so commonly found around us that "you probably ate it this morning," said Stukus. "It is in many different foods and medications. It's in in MiraLAX, for when people are constipated. It's present in some other vaccines as well."
Concerns about allergic reactions were raised when two people in the United Kingdom who received the vaccine in the first day it was distributed experienced severe allergic reactions known as anaphylaxis. But both of these people had a history of severe reactions, and both carried devices like an Epi Pen.
"We lack details about these people including their own medical history of allergy and anaphylaxis or their exact symptoms," Stukus said.
"What struck me about the cases in the U.K. was that they already had carried EpiPens," Reigh said. It is most probable that these two persons already had a history of and predisposition to anaphylaxis.
Dr. Anthony Fauci Thursday said people who are prone to these types of severe allergic reactions might want to get their vaccine at a medical facility that's equipped to take care of them, in case they experience a severe reaction.
But for everyone else -- even those with a history of less severe allergies -- the vaccine should be of no concern, experts say.