They added a blood acid reducer which is used to stabilize people with heart attacks.
Authorization is being requested for a modified formulation of the Pfizer?BioNTech COVID-19 Vaccine. Each dose of this formulation contains 10 ?g of a nucleoside-modified messenger RNA (mRNA) encoding the viral spike (S) glycoprotein of SARS-CoV-2 that is formulated in lipid particles and supplied as a frozen suspension in multiple dose vials.
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) buffer instead of the phosphatebuffered saline (PBS) as used in the previous formulation and excludes sodium chloride and potassium chloride. The packaged vials for the new formulation are stored frozen at -90°C to – 60°C. The frozen vials may be thawed and stored at refrigerator at 2°C to 8°C for up to 10
The Pfizer?BioNTech COVID-19 Vaccine does not contain preservative. The vial stoppers are not made with natural rubber latex. For the 10-?g RNA dose, each 1.3-mL filled via vial must be diluted with 1.3mL 0.9% sodium chloride for injection to provide 10 doses at 10 ?g RNA / 0.2 mL Injection volume. After dilution, the vials should be stored at 2°C to 25°C and should be used within 12 hours.
Page 14 of this PDF. FDA
Tromethamine (Tris) Google