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Drew Weissman

Modified mRNA Technology Used in COVID-19 Vaccines

US Patent No. 8,278,036
Inducted in 2022
Born September 7, 1959

Fundamental research and discoveries by immunologist Drew Weissman and biochemist Katalin Karikó laid a critical piece of the foundation for the messenger RNA (mRNA) COVID-19 vaccines developed by Pfizer-BioNTech and Moderna. The mRNA vaccines have been crucial in the fight against the respiratory disease caused by SARS-CoV 2, a coronavirus discovered in 2019. Nearly 1 billion mRNA vaccine doses have been administered worldwide since December 2020.

mRNA is genetic material in the human body that instructs cells to make proteins. The modified, synthetic mRNA in the COVID-19 vaccines is delivered into the human body and instructs cells to make copies of the spike protein of the virus. If someone is later exposed to the real virus, their body’s immune system will recognize it and will rapidly trigger an immune response to protect against severe disease.

In the early 2000s at the University of Pennsylvania, Weissman and Karikó discovered that replacing one of the four building blocks of mRNA molecules, uridine, with pseudouridine created a modified mRNA with favorable qualities and reduced adverse reactions. Unmodified mRNA molecules are unable to slip past the body’s immune system. Weissman and Karikó’s changes allowed the resulting modified mRNA to avoid immediate detection, remain active longer and enter into cells to efficiently instruct them to create antigens or other proteins that fight or treat disease. This fundamental discovery paved the way for modified mRNA to be potentially used in a wide array of future vaccines and treatments.

Weissman serves as the Roberts Family Professor in Vaccine Research at the Perelman School of Medicine at the University of Pennsylvania. He came to Penn in 1997, and his collaboration with Karikó began soon afterward. Prior to 1997, Weissman completed a fellowship at the National Institute of Allergy and Infectious Diseases of the National Institutes of Health. Weissman received his bachelor’s and master’s degrees from Brandeis University (1981), his M.D./Ph.D. from Boston University (1987) and completed his residency in internal medicine at Beth Israel Hospital in Boston in 1990.

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