Drew Weissman

Drew Weissman
Weissman at 2024 Nobel Week
Drew Weissman
Born	7 9, 1959
Birthplace	Lexington, Massachusetts, U.S.
Nationality	American
Occupation	Physician, immunologist, professor
Employer	University of Pennsylvania
Known for	Modified mRNA technologies used in COVID-19 vaccines
Education	MD, PhD (Boston University)
Awards	Nobel Prize in Physiology or Medicine (2023), Lasker–DeBakey Clinical Medical Research Award (2021), Princess of Asturias Award for Technical and Scientific Research (2021)
Website	[https://www.pennmedicine.org/providers/profile/drew-weissman Official site]

Drew Weissman (born September 7, 1959) is an American physician and immunologist whose research into the modification of messenger RNA (mRNA) laid the scientific foundation for a new class of vaccines, including those deployed against COVID-19. Born in Lexington, Massachusetts, Weissman pursued a career in immunology that would ultimately intersect with one of the most consequential developments in modern medicine. Alongside Hungarian-American biochemist Katalin Karikó, he discovered that chemical modifications to nucleoside bases in synthetic mRNA could suppress the inflammatory immune responses that had long stymied efforts to use mRNA therapeutically. This finding, published in the mid-2000s, became the key enabling technology behind the mRNA COVID-19 vaccines produced by BioNTech/Pfizer and Moderna, which were administered to billions of people worldwide during the pandemic. Weissman serves as the inaugural Roberts Family Professor in Vaccine Research, director of the Penn Institute for RNA Innovation, and professor of medicine at the Perelman School of Medicine at the University of Pennsylvania. In 2023, he and Karikó were awarded the Nobel Prize in Physiology or Medicine "for their discoveries concerning nucleoside base modifications that enabled the development of effective mRNA vaccines against COVID-19."

Early Life

Drew Weissman was born on September 7, 1959, in Lexington, Massachusetts, a suburb of Boston known for its historical significance in the American Revolution. He grew up in the greater Boston area in a family that valued education and intellectual inquiry. Details about his parents and siblings remain largely private, as Weissman has typically directed public attention toward his scientific work rather than his personal background.

From an early age, Weissman developed an interest in science. Growing up during an era of significant advances in molecular biology and immunology—the decades following the elucidation of DNA's structure and the development of transformative vaccines—he was drawn to understanding the mechanisms of the human immune system. His formative years in Massachusetts placed him in proximity to some of the nation's leading academic and research institutions, an environment that would shape his educational and professional trajectory.

Education

Weissman pursued his undergraduate studies at Brandeis University, located in Waltham, Massachusetts, where he studied biochemistry and enzymology. Brandeis, with its strong emphasis on the sciences and its proximity to the broader Boston academic ecosystem, provided a rigorous foundation for his future work.

He subsequently enrolled at Boston University, where he undertook a combined MD/PhD program. His doctoral research focused on immunology, and his dissertation, titled Regulation of B Lymphocytes with Reagents that Cross-link Surface Immunoglobulin, was completed in 1987 under the supervision of Ann Marshak-Rothstein. This work examined mechanisms by which B cells—a critical component of the adaptive immune system responsible for antibody production—could be regulated through receptor cross-linking, a topic that would inform his later understanding of immune responses to foreign molecules, including synthetic RNA.

After earning both his MD and PhD degrees from Boston University, Weissman pursued postdoctoral training at the National Institutes of Health (NIH), where he worked in the laboratory of Anthony Fauci, then the director of the National Institute of Allergy and Infectious Diseases (NIAID). During this period, Weissman focused on the biology of dendritic cells and other components of innate immunity, research that deepened his understanding of how the immune system recognizes and responds to pathogens and foreign nucleic acids.

Career

Early Academic Career and Arrival at Penn

Following his training at the NIH, Weissman joined the faculty of the University of Pennsylvania Perelman School of Medicine in the late 1990s, where he established a laboratory focused on the biology of dendritic cells and the innate immune system. At Penn, Weissman's interests centered on understanding how the immune system detects and responds to nucleic acids, particularly RNA. Dendritic cells serve as sentinels of the immune system, recognizing molecular patterns associated with pathogens and initiating immune responses. Weissman's expertise in this area positioned him to investigate a fundamental question: why did synthetic mRNA injected into cells trigger a potent and often counterproductive inflammatory response?

It was at Penn that Weissman's career took a pivotal turn. In the late 1990s, he met Katalin Karikó, a Hungarian-born biochemist who had spent years pursuing the therapeutic potential of mRNA despite facing persistent skepticism from the scientific establishment and repeated rejections of her grant applications. The two researchers struck up a conversation at a photocopier—a chance encounter that would become one of the most consequential meetings in modern biomedical science.

Breakthrough in Nucleoside-Modified mRNA

The central challenge confronting the therapeutic use of mRNA was that synthetic mRNA, when introduced into mammalian cells, triggered a strong innate immune response. Toll-like receptors and other pattern-recognition receptors in cells identified synthetic mRNA as foreign, leading to inflammation and degradation of the mRNA before it could be translated into the desired protein. This inflammatory reaction rendered synthetic mRNA essentially useless as a therapeutic tool, and many researchers had abandoned the field as a result.

Weissman and Karikó hypothesized that the problem lay in the specific chemical structure of the synthetic mRNA's nucleosides. Natural mRNA in mammalian cells contains numerous chemically modified nucleosides—subtle variations that distinguish it from viral or bacterial RNA. They reasoned that incorporating similar modifications into synthetic mRNA might allow it to evade the innate immune sensors.

Through a series of experiments conducted at Penn in the early and mid-2000s, Weissman and Karikó demonstrated that replacing uridine in synthetic mRNA with pseudouridine—a naturally occurring modified nucleoside—dramatically reduced the inflammatory immune response. Their landmark paper, published in 2005, showed that nucleoside-modified mRNA was not only less immunogenic but was also translated more efficiently into protein by cellular machinery. Subsequent studies by the pair showed that the modified mRNA could be used to direct cells to produce specific proteins at therapeutically relevant levels, opening the door to a wide range of potential medical applications, from vaccines to protein-replacement therapies.

These findings were initially met with limited attention from the broader scientific community and the pharmaceutical industry. The concept of mRNA therapeutics remained on the margins of mainstream drug development for several years. Nevertheless, Weissman and Karikó continued to refine their technology, securing key patents on nucleoside-modified mRNA and its applications.

Development of mRNA Vaccine Platform

Building on the nucleoside-modification discovery, Weissman's laboratory at Penn developed and refined a platform for using modified mRNA encapsulated in lipid nanoparticles as a vaccine delivery system. In this approach, the modified mRNA is packaged in tiny lipid-based carriers that protect it and facilitate its entry into cells. Once inside, the mRNA instructs cells to produce a protein antigen—such as a viral spike protein—that stimulates the adaptive immune system to mount a protective response without causing disease.

Weissman's team demonstrated the efficacy of this approach in preclinical studies against a variety of infectious diseases, including influenza, HIV, and Zika virus. A 2015 study published in Nature provided further evidence of the potential of nucleoside-modified mRNA vaccines, showing robust immune responses in animal models. These preclinical results attracted the attention of biotechnology companies, including Moderna and BioNTech, which licensed the technology and began developing their own mRNA vaccine candidates for various diseases.

COVID-19 Pandemic and Global Impact

When the SARS-CoV-2 virus emerged in late 2019 and rapidly spread across the globe, the mRNA vaccine platform that Weissman and Karikó had developed over the preceding two decades was uniquely positioned for rapid deployment. The genetic sequence of the virus was published by Chinese researchers in January 2020, and within days, scientists at Moderna and BioNTech/Pfizer were able to design mRNA vaccine candidates targeting the virus's spike protein using the nucleoside-modification technology pioneered by Weissman and Karikó.

Both the Pfizer-BioNTech vaccine (BNT162b2) and the Moderna vaccine (mRNA-1273) received emergency use authorization in December 2020, less than a year after the pandemic began—an unprecedented timeline for vaccine development. Clinical trials demonstrated efficacy rates exceeding 90 percent in preventing symptomatic COVID-19, and the vaccines were subsequently administered to billions of people worldwide. The rapid development and deployment of these vaccines is estimated to have saved millions of lives during the pandemic.

Weissman has spoken publicly about the significance of this outcome, emphasizing that it was the result of over two decades of basic research. In a 2025 interview with Penn Medicine, he discussed his scientific journey and the persistence required to bring the mRNA technology from a laboratory curiosity to a global public health tool.

Post-Pandemic Research

Following the success of the COVID-19 vaccines, Weissman continued to expand the applications of mRNA technology at the University of Pennsylvania. As director of the Penn Institute for RNA Innovation, he has overseen research into mRNA-based treatments and vaccines for a range of diseases and conditions beyond infectious disease.

In 2025, Weissman's laboratory, in collaboration with researchers at Cincinnati Children's Hospital Medical Center, published research demonstrating that mRNA vaccines encapsulated in lipid nanoparticles could prevent severe allergic reactions in mice. The study showed that the nanoparticle-based vaccines were able to stop allergens from triggering dangerous immune reactions and life-threatening inflammation, raising the prospect that mRNA technology could one day be used to treat or prevent food and seasonal allergies in humans.

Weissman has also been active in public discourse about pandemic preparedness. Speaking at a McGill University event in October 2025, he expressed concern that the world was insufficiently prepared for the next pandemic. "The biggest concern to me now is that for the next pandemic—and there will definitely be another one—we are not going to be prepared," he stated, urging continued investment in mRNA research and vaccine infrastructure.

In September 2025, Weissman addressed concerns raised at a meeting of federal vaccine advisers about the persistence of mRNA from COVID-19 vaccines in the body, stating in an interview with STAT News that such claims were "absolutely impossible" based on the known biology of mRNA degradation.

Academic Positions

Throughout his career at the University of Pennsylvania, Weissman has held several academic appointments. He serves as the inaugural Roberts Family Professor in Vaccine Research, a named chair recognizing his contributions to the field. He is also the director of the Penn Institute for RNA Innovation and holds the rank of professor of medicine at the Perelman School of Medicine. In addition to his research, Weissman has delivered numerous invited lectures at academic institutions. In March 2025, he was invited to present the Senior Vice Chancellor Laureate Lecture at the University of Pittsburgh.

Personal Life

Weissman has maintained a relatively private personal life, directing most of his public appearances and interviews toward discussion of his scientific work and its implications for public health. He resides in the Philadelphia area, where he has lived since joining the faculty of the University of Pennsylvania. In interviews, he has described himself as driven by curiosity about immunology and a desire to develop therapies that address unmet medical needs. He has spoken publicly about the long years of limited recognition and funding that preceded the COVID-19 pandemic, noting that he and Karikó pursued their mRNA research during a period when the field attracted little mainstream interest or support.

Recognition

The discoveries made by Weissman and Karikó received increasing recognition as the impact of their work became apparent during the COVID-19 pandemic. The pair received numerous awards and honors, culminating in the Nobel Prize.

In 2021, Weissman and Karikó were awarded the Lasker–DeBakey Clinical Medical Research Award, one of the most prestigious prizes in American medicine, "for their pioneering research on nucleoside modifications of mRNA, leading to the development of effective COVID-19 vaccines." That same year, they were among the recipients of the Princess of Asturias Award for Technical and Scientific Research, shared with other scientists who contributed to the development of COVID-19 vaccines, including Philip Felgner, Uğur Şahin, Özlem Türeci, Derrick Rossi, and Sarah Gilbert.

Also in 2021, Weissman received the Albany Medical Center Prize in Medicine and Biomedical Research, one of the largest prizes in medicine in the United States.

In 2022, Weissman was elected to the National Academy of Medicine and the American Academy of Arts and Sciences, two of the highest professional honors available to American scientists and physicians.

Weissman and Karikó were jointly awarded the Louisa Gross Horwitz Prize by Columbia University, which has historically been a precursor to the Nobel Prize for many of its recipients.

The Rosenstiel Award for Distinguished Work in Basic Medical Sciences was also awarded to Weissman, recognizing his contributions to the understanding of RNA biology and its medical applications.

In 2023, Weissman and Karikó received the Nobel Prize in Physiology or Medicine "for their discoveries concerning nucleoside base modifications that enabled the development of effective mRNA vaccines against COVID-19." The Nobel Assembly at Karolinska Institutet noted that their discoveries were "critical for developing effective mRNA vaccines against COVID-19 during the pandemic that began in early 2020."

Legacy

Drew Weissman's work, conducted in partnership with Katalin Karikó, represents a foundational contribution to the field of RNA therapeutics. Their discovery that nucleoside modifications to synthetic mRNA could suppress innate immune responses and enhance protein production resolved a problem that had prevented the therapeutic use of mRNA for decades. This breakthrough enabled the rapid development of the mRNA COVID-19 vaccines by BioNTech/Pfizer and Moderna, which were instrumental in the global response to the COVID-19 pandemic.

The mRNA platform has implications well beyond COVID-19 vaccination. Researchers are now applying the technology to develop vaccines and therapies for a range of conditions, including influenza, respiratory syncytial virus (RSV), HIV, cancer, autoimmune diseases, and allergies. Weissman's ongoing research at the Penn Institute for RNA Innovation continues to explore these applications, including recent work on mRNA-based treatments for allergic disease.

The story of Weissman and Karikó's collaboration is also frequently cited as a case study in the importance of sustained funding for basic research. For many years, their work attracted limited attention and support, and Karikó faced repeated setbacks in securing grants. The eventual success of their research during a global health crisis underscored the unpredictable but potentially transformative value of curiosity-driven science.

Weissman's contributions have been recognized by election to leading scientific academies and by the receipt of the Nobel Prize, the Lasker Award, and other honors. His work has fundamentally altered the landscape of vaccine development and opened a new chapter in the use of RNA-based technologies in medicine.