To provide a vaccine with an improved stability profile, the Pfizer-BioNTech COVID-19 Vaccine for use in children 5-11 years of age uses tromethamine (Tris) Tromethamine (Tris) is a blood acid reducer which is used to stabilize people with heart attacks. Here are known side effects: Respiratory depression, local irritation, tissue inflammation, injection site infection, febrile response, chemical phlebitis, venospasm (vein spasms), hypervolemia, IV thrombosis, extravasation (with possible necrosis and sloughing of tissues), transient decreases in blood glucose concentrations, hypoglycemia, and hepatocellular necrosis with infusion via low-lying umbilical venous catheters https://presscalifornia.com/2021/10/28/pfizer-vax-kids/