The claim is part of a conspiracy theory being spread against Pfizer vaccines. The vaccine is found to be safe and effective.
Despite that, various claims are being circulated on social media discrediting the vaccine's efficacy, one of which stated, "Europeans are seriously scared by the fact that the Pfizer vaccine's composition during clinical trials was different from what went on to commercial production."
Pfizer had four BNT162 vaccine candidates during the pre-clinical and clinical trials. Out of these four candidates, BNT162b1 and BNT162b2 showed promising results, and these two MRNA-based vaccine candidates got a fast track designation by the USFDA. Pfizer made a final call based on the vaccine candidates' safety assessment and immunity response. Thus the BNT162b2 became the main vaccine candidate during the phase 3 trials conducted by Pfizer. This BNT1662b2 became the Pfizer vaccine which is currently being produced for vaccine administration in various countries.
However, the vaccine was approved by the US FDA after a complete analysis of the trial results and was done by a team of experts. Furthermore, the claim about the different compositions used during the commercial production of vaccines is baseless and has no evidence. The conclusion derived from the phase 3 study of the COVID-19 vaccine announced by Pfizer and BioNTech is found to be safe, and experts agree that the listed ingredients in the Pfizer shot are pretty standard.
Thus we can conclude that the composition of the Pfizer vaccine currently being produced has undergone extensive analysis and clinical studies and has been certified to be safe.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.