evidence: The Pfizer–BioNTech COVID-19 vaccine, sold under the brand name Comirnaty,[2][33] is an mRNA-based COVID-19 vaccine developed by the German biotechnology company BioNTech. For its development, BioNTech collaborated with the American company Pfizer to carry out clinical trials, logistics, and manufacturing.[45][46] It is authorized for use in humans to provide protection against COVID-19, caused by infection with the SARS-CoV-2 virus.[2][31] The vaccine is given by intramuscular injection.[35] It is composed of nucleoside-modified mRNA (modRNA) that encodes a mutated form of the full-length spike protein of SARS-CoV-2, which is encapsulated in lipid nanoparticles.[47] Initial guidance recommended a two-dose regimen, given 21 days apart;[35][48][49][50] this interval was subsequently extended to up to 42 days in the United States,[35][51] and up to four months in Canada.[52][53] [...] The Pfizer–BioNTech COVID-19 vaccine is used to provide protection against COVID-19, caused by infection with the SARS-CoV-2 virus, by eliciting an immune response to the S antigen.[1][2][31][40] The vaccine is used to reduce morbidity and mortality from COVID-19.[35]