The Pfizer vaccine is an mRNA vaccine originally approved for EUA by the FDA on December 11, 2020. In 2022, the vaccine was replaced with a bivalent formula aimed to prevent infection by the original strain of the virus and Omicron variants BA.4 and BA.5. The EUA was again amended on September 11, 2023, to include the 2023–2024 formula, which includes a monovalent (single) component that corresponds to the Omicron variant XBB.1.5. The original and bivalent vaccines are no longer in use. The 2023–2024 formula is authorized for individuals 6 months through 11 years of age to prevent COVID-19. COMIRNATY (2023–2024 formula) is the licensed Pfizer product for people 12 years and older.
Side effects of the Pfizer-BioNTech vaccine are typically minimal and may include one or more of the following: pain, redness and swelling in the injected arm, fatigue, headache, muscle pain, chills, fever, and nausea. The side effects normally occur within a day or two after getting the vaccine and go away within a few days. These side effects are usually normal signs that the body is building immune protection.
Based on clinical trials, the original Pfizer-BioNTech vaccine was shown to be 95% effective at preventing COVID-19 infection in people receiving two doses of the vaccine. It was also found to be highly effective in preventing infection among people of diverse age, sex, race, and ethnicity, as well as among people with underlying medical conditions.
Because this is an mRNA vaccine, there is no live virus in the vaccine; therefore, the vaccine cannot give COVID-19 to the individual. Also, since the mRNA contained in the vaccine is broken down and removed, the vaccine does not interact with or affect the recipient's DNA.
