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Here's what you need to know about the ingredient added to Pfizer's vaccine for kids

Tromethamine, or 'Tris,' is a common buffer that was added to Pfizer's COVID vaccine for children. It keeps the pH level stable, while extending the shelf life.

WASHINGTON — More than 59% of Americans are fully vaccinated against COVID-19, according to the Centers for Disease Control and Prevention. That number is expected to increase, as vaccination data for kids ages 5-11 are tabulated in the coming days.

Still, that means potentially more than 100 million people remain unvaccinated in the U.S. A big reason is vaccine hesitancy, partially driven by online misinformation.

On social media, lots of people are talking about a drug used to treat heart attacks called "Tromethamine," which they say was added to the child-sized dose of the Pfizer vaccine.

"Pfizer adds chemical Tromethamine to the child vaccines--a blood acid reducer used to stabilize people with heart attacked, Ok, that's bad," a tweet with 25,000 likes reads.

Another video with more than 50,000 likes and 25,000 shares shared the same concerns.

"They've replaced the saline buffer in the vaccine with a medication called 'Tromethamine,'" one tiktok user said. "It's a blood acid reducer, it has a lot of potentially serious side effects...That doesn't seem like a minor change. Do you think that's a minor change? Why do kids need heart attack medication who are getting this vaccine?"


#greenscreen #fyp #PUBGMOBILE #PINKHolidayRemix #tromethamine #why that'sweird

♬ original sound - rkoverit

People are claiming Tromethamine was added to the child Pfizer doses; wasn't tested on kids in the clinical trial but was still authorized by the FDA; and was added to counteract heart problems caused by the vaccine itself.

So we're Verifying the authenticity of these claims. 


  • Dr. Peter Marks- director of the Center for Biologics Evaluation and Research at the Food & Drug Administration- press conference 10/20/2021
  • Pfizer Fact Sheets for Healthcare Providers and Recipients/Caregivers
  • Dr. William Gruber- Senior Vice President of Pfizer Vaccine Clinical Research and Development
  • Dr. Andrea Berry, infectious disease pediatrician at the University of Maryland Children's Hospital and associate professor of Pediatrics at the University of Maryland School of Medicine
  • Dr. Kawsar Talaat, infectious disease physician at Johns Hopkins Medicine and an associate professor at the Johns Hopkins Bloomberg School of Public Health
  • Dr. Donald Alcendor, associate professor at Meharry Medical College and associate adjunct professor at Vanderbilt University Medical Center


Was Tromethamine added to the kid's Pfizer doses?


This is true.

Yes, that's true.

The change was noted several times during the FDA advisory committee's meeting as well as following the meeting in a news conference.

"The new formulation contains Tromethamine, which is known as 'Tris' buffer, and it's commonly used as a buffer in a variety of other FDA-approved vaccines and biologics including products for use in children," Dr. Marks said. "The FDA evaluated manufacturing data to support the change in this inactive ingredient and concluded it did not impact the safety or effectiveness of the product. "

Buffers are commonly added to vaccines to help maintain a vaccine’s pH level, making sure it doesn't become too acidic or too alkaline. Buffers allow the vaccine to last longer, meaning without it, a vaccine would degrade faster over time.


Is it true that Tromethamine was not in the doses given in the clinical trial?


This is true.

Yes, that's also true. 

Dr. Gruber, who represented Pfizer in FDA's advisory committee meeting, said that the clinical trial doses contained a different buffer.

"The studies were done using the same volumes 0.2 milliliters that is in the final presentation used in terms of the dose, but contain the PBS buffer," he said. "We obviously had extensive consultations with the FDA and it was determined that clinical studies were not required again because the LNP and the mRNA were the same, and the behavior in terms of reactogenicity and efficacy are expected to be the same."

So yes, one buffer was tested, but another one was authorized for use. 

Our Verify researchers spoke to three medical experts who all say they are not concerned for the following reasons: 

  1. The FDA committee knew about the buffer change 
  2. Tris is in other FDA-authorized and approved vaccines including the Moderna COVID and ERVEBO Ebola vaccine 
  3. None of the active ingredients have been changed 
  4. The amount of Tris in each dose is a trace amount

"It doesn't concern me because the FDA reviewed that information and the FDA said it was okay, and because I know that Tris and Tromethamine is a common buffer," Dr. Andrea Berry, infectious disease pediatrician at the University of Maryland Children's Hospital, said. "I know that it's in other medicines, and it's in other vaccines, So those things all make it not concern me."

Dr. Alcendor and Dr. Talaat agreed. 

Credit: WUSA
Our Verify researchers spoke to a trio of infectious disease experts

"Tris or Tromethamine is a buffer that's used in many, many products, and is just used to stabilize things so that the vaccine can be put in refrigerator temperatures for longer—so instead of four weeks in the refrigerator it can stay in the refrigerator for 10 weeks," Dr. Talaat, a clinical vaccine trial expert and associate professor at Johns Hopkins University, said. "The FDA does not consider this addition to be a change in the manufacturing. So they did not think that this was a significant change, because they've already approved many products for adults and children that contained this buffer."

Our Verify researchers also discovered that there is an adult Pfizer vaccine with a gray cap that includes Tris/Tromethamine. As of November 19, the gray cap version "is not yet available in the United States," according to the FDA

This gray cap formulation does not require dilution, unlike the purple cap-adult version and orange cap-child version.

RELATED: Here's how Pfizer COVID vaccines for children are prepared


Tromethamine, in its drug form called 'Tham,' is a drug prescribed to heart attack patients. Therefore, some people online claim that Tromethamine was added to the vaccine to counteract heart-related side effects from the vaccine. Is that true?


This is false.

No, this claim is false.

“This tiny amount of tromethamine, that is put into these vaccine bottles, that is to stabilize the pH of the bottle...it doesn't have anything to do with the pH of the person that vaccine is going into," Dr. Berry said. "And I'm not worried at all about the Pfizer vaccine causing any kind of heart attacks in kids."

Dr. Alcendor explained that the amount of Tromethamine in the vial is very tiny, and is not at the concentration prescribed to those with heart disorders.

“It would be considered another trace element that would be in a vaccine formulation, that is at the level that is unlikely to cause any adverse effects," Dr. Alcendor said.

They all agree the reason Tromethamine was added to the vaccine was to extend the shelf life of the vaccine, it was not added to counteract side effects caused by the vaccine itself.

RELATED: VERIFY: What ingredients are in the COVID-19 vaccines?

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