After months of waiting, Pfizer's COVID-19 vaccine is finally being given to people across the country—starting with health care workers and residents of long-term care facilities.
While those outside of that first group won't be vaccinated for weeks or even months, it's still understandable for every person who will be eligible to get the vaccine to have questions about it—specifically surrounding the ingredients that make up the jab. Since the Pfizer vaccine was officially approved by the US Food and Drug Administration for emergency use on December 11, the ingredients of that vaccine have become available for the public to view online. Here's what you need to know.
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First, some basics about how Pfizer’s COVID-19 vaccine works
The Pfizer COVID-19 vaccine is made using a newer technology called messenger RNA (mRNA). The Moderna COVID-19 vaccine, which is also expected to be authorized for emergency use by the FDA soon, uses mRNA technology, too.
An mRNA vaccine works by encoding a portion of the spike protein found on the surface of SARS-CoV-2, the virus that causes COVID-19, per the Centers for Disease Control and Prevention (CDC). These mRNA vaccines use pieces of the encoded protein to create an immune response in your body, which then develops antibodies. (In case you're not familiar with them, antibodies are proteins made by your immune system to fight infections like viruses. They can also help fend off future illnesses by those same infections.)
After the vaccine prompts an immune response, your body will eliminate the protein and the mRNA. However, the antibodies will stay put—it's just not known at this point how long they'll last.
What’s in Pfizer’s COVID-19 vaccine?
When the Pfizer COVID-19 vaccine received an EUA from the FDA, its ingredients list was published online in a fact sheet for vaccine recipients and caregivers. This is the full list of ingredients, according to the FDA:
- mRNA
- Lipids (including ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 2 [(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 1,2-Distearoyl-sn-glycero-3- phosphocholine, and cholesterol)
- Potassium chloride
- Monobasic potassium phosphate
- Sodium chloride
- Dibasic sodium phosphate dehydrate
- Sucrose
The mRNA we've already covered, but the lipids are also a crucial element. "The lipids, which are fats, are very important because they form a little spherical shell around that mRNA," William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells Health.
The lipids are "how the vaccine is delivered to your body and to your cells," infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, tells Health.
Lipids "help keep the mRNA intact and stable until it gets into your body and starts doing its work," Dr. Schaffner says. After that, they dissolve and are removed by your body. Because of that, lipids are "unique" to this type of vaccine, Jamie Alan, PhD, an assistant professor of pharmacology and toxicology at Michigan State University, tells Health. But, she says, "the rest of the ingredients are very common in vaccines."
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The potassium chloride, monobasic potassium phosphate, sodium chloride, and dibasic sodium phosphate dehydrate are used to maintain pH and stability of the vaccine, Alan says. (Sodium chloride is just salt, Dr. Adalja points out.) And the sucrose, which is a form of sugar, is "usually used as a stabilizer," Alan says.
Overall, experts say the vaccine ingredients make sense. "There is nothing on this ingredients list that is shocking," Dr. Schaffner says, only adding to the evidence that the Pfizer COVID-19 vaccine—and any other COVID-19 vaccines that will be approved by the FDA for emergency or public use—are safe to use.
The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.
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