BNT162b1 is an experimental mRNA vaccine developed by BioNTech in collaboration with Pfizer to protect against the SARS-CoV-2 virus, which causes COVID-19. This vaccine works by using messenger RNA to instruct cells in the body to produce a harmless piece of the virus, prompting an immune response. The immune system then recognizes this piece as foreign and generates antibodies, preparing the body to fight off the actual virus if exposed. BNT162b1 was part of the early vaccine candidates evaluated in clinical trials, contributing to the rapid development of effective vaccines against the pandemic.