By Jonathan Corum and Carl Zimmer Updated Jan. 9, 2021
Researchers are testing 64 coronavirus vaccines in clinical trials on humans. Here are explanations about how nine of the leading vaccines work.
Messenger RNA Vaccines
The vaccine, known as Comirnaty, has been approved or authorized for emergency use in many countries, including the United States. Clinical trials showed the vaccine has an efficacy of 95 percent.
The vaccine, known as mRNA-1273, has been approved in Canada and authorized for emergency use in the United States, Israel and the European Union. Clinical trials showed the vaccine has an efficacy of 94.5 percent.
Adenovirus-Based Vaccines
The vaccine, known as AZD1222 or Covishield, is authorized for emergency use in Britain, India, Mexico and other countries. Clinical trials showed the vaccine has an efficacy of 62 to 90 percent, depending on dosage.
The vaccine, called Ad26.COV2.S, is in Phase 3 trials and has not been authorized by any country. Trial results are expected in January.
The vaccine, known as Sputnik V or Gam-Covid-Vac, is a combination of two different Adenoviruses, Ad26 and Ad5. The vaccine is in use in Russia, Belarus and several other countries. A Phase 3 trial showed an efficacy of 91 percent.