Tromethamine is a stabilizing agent used to increase the storage time for pharmaceutical products, but not to stabilize a heart attack.
However, in the Pfizer and Moderna COVID-19 vaccines, tromethamine is used as a "buffer" for long-term storage. According to USA Today, "Tris buffers help maintain a vaccine's pH, or acidity, and stability, but they aren't used to stop heart attacks."
On October 29, 2021, the U.S. Food and Drug Administration (FDA) issued the Emergency Use Authorization of the Pfizer-BioNTech COVID-19 vaccine for children five years of age and older. The FDA also authorized a manufacturing change to include a new formula for Pfizer’s vaccines that uses tromethamine buffer instead of phosphate-buffered saline used initially in the authorized Pfizer vaccine. The use of the tris buffer helps stabilize the vaccine under refrigerated temperatures for 10 weeks.
The FDA also said Pfizer’s clinical trials show the new vaccine formulation containing tromethamine does not impact the safety or effectiveness of the vaccine. Furthermore, Pfizer’s COVID-19 vaccine for individuals above 12 years of age also contains tromethamine.
There is no evidence that tromethamine was added in Pfizer’s vaccines to stabilize patients from any adverse health effects of the COVID-19 vaccines, including heart attack.
Heart problems related to COVID-19 vaccines are very rare, mild, and resolves quickly. The potential benefits of COVID-19 vaccination outweigh the potential risks, including myocarditis or pericarditis, CDC reported.