In the United States, there are four COVID vaccines that have been authorized for use: Pfizer, Moderna, Novavax, and Johnson & Johnson.
The Pfizer and Moderna vaccines are mRNA vaccines, each requiring two doses. Your second dose will be three to eight weeks after the first dose.
The Johnson & Johnson vaccine is authorized for limited use only – for adults 18 or over who cannot or will not receive any other type of COVID vaccine. If you are considering a Johnson & Johnson vaccine, please consult with your doctor to see if this is a good choice for you.
The Novavax vaccine is a protein subunit vaccine that requires two doses. Your second dose will be three to eight weeks after the first dose.
https://www.yalemedicine.org/news/covid-19-vaccine-comparison (Yale Medicine)