Blood & Cancer

How do the various COVID-19 vaccines work, and when should patients be vaccinated? We tackle these topics and more in this episode. Our host David H. Henry, MD, is joined by Drew Weissman, MD, PhD, a professor at the University of Pennsylvania, Philadelphia. Dr. Weissman codeveloped the messenger RNA (mRNA) technology being used in the COVID-19 vaccines produced by Pfizer/BioNTech and Moderna. History of mRNA vaccines Testing of mRNA vaccines began in the 1990s. An initial problem with these vaccines was that the RNA was highly inflammatory. Dr. Weissman and his colleague, Katalin Karikó, PhD, discovered how to fix that problem in 2005. The pair found that placing modified nucleosides into mRNA made it noninflammatory and allowed for increased production of protein from the RNA – up to a 1,000-fold increase in mice. This technology is the basis of the Moderna and Pfizer/BioNTech COVID-19 vaccines. Immunology and vaccines To produce a good immune response, antigen must be present for a long time, though t