Promising Results of Next-Generation Intranasal COVID-19 Booster Vaccine: Implications for Infection Prevention and Transmission
The Icahn School of Medicine at Mount Sinai in New York, NY is pleased to announce that CastleVax, Inc. has completed enrollment and a preliminary analysis of a phase 1 trial of its licensed Newcastle disease virus (NDV)-based COVID-19 booster vaccine.
The phase 1 study evaluated two dose levels of the live, recombinant vaccine, NDV-HXP-Spike(S), delivered intranasally, intramuscularly, or via both routes in combination, in participants previously vaccinated with an authorized intramuscular COVID-19 vaccine.
Interim results show that intranasal delivery resulted in a robust S-specific, secretory IgA response in saliva relative to pre-booster levels, which is important for conferring mucosal immunity and has the potential to prevent infection and/or transmission of COVID-19. In addition, a strong boosting of serum neutralizing-antibody response was observed, which is important for conferring systemic immunity and prevention of severe disease, hospitalization, and death (the efficacy endpoint(s) for currently authorized intramuscularly delivered vaccines). The safety profile was also acceptable, successfully clearing Data Safety Monitoring Board reviews.
“The initial observations from our phase 1 trial of NDV-HXP-S as a COVID-19 booster vaccination suggest that it is safe and well-tolerated when delivered intranasally and/or intramuscularly to healthy adults. The preliminary exploratory findings looking at mucosal and systemic antibody responses are encouraging, particularly when NDV-HXP-S is administered intranasally. There is a growing interest in developing vaccines that not only protect against the severe illnesses caused by respiratory pathogens but also limit host susceptibility and decrease person-to-person transmissions by enhancing the mucosal immune response. I am excited to watch as the NDV-vectored vaccine platform matures to address newer variants of concern in larger randomized controlled trials,” said Sean Liu, MD, PhD, Assistant Professor of Medicine (Infectious Diseases and Hospital Medicine) at Icahn Mount Sinai.
“We are thrilled with the progress led by Dr. Liu and our colleagues at the Mount Sinai Health System, and are both excited and encouraged by these preliminary results,” said Michael Egan, PhD, CastleVax Chief Scientific Officer and acting Chief Executive Officer. “Dr. Liu’s preliminary findings complement those of our development partners in Mexico, Avimex, whose interim phase 3 results showed their live, attenuated NDV-based vaccine (Patria® (AVX/COVID-12), licensed from CastleVax, was effective as a booster against COVID-19.”
The Mount Sinai NDV-vectored vaccine platform was developed by Mount Sinai scientists Peter Palese, PhD, Horace W. Goldsmith Professor and Chair Emeritus of Microbiology; Adolfo García-Sastre, PhD, Irene and Dr. Arthur M. Fishberg Professor of Medicine and Director of the Global Health and Emerging Pathogens Institute; Florian Krammer, PhD, Professor of Microbiology, and Pathology, Molecular and Cell Based Medicine; and Weina Sun, PhD, Assistant Professor of Microbiology, Icahn Mount Sinai, and was licensed by Mount Sinai to CastleVax Inc. Mount Sinai has a financial interest in this technology and in CastleVax. Drs. Palese, García-Sastre, Krammer, and Sun also have a financial interest in this technology and in CastleVax pursuant to the Mount Sinai Intellectual Property Policy. Mount Sinai is represented on the CastleVax Board of Directors by Erik Lium, PhD, Chief Commercial Innovation Officer, Mount Sinai Health System, and President, Mount Sinai Innovation Partners; Mr. Matthew Rosamond, Chief Financial Officer, Icahn Mount Sinai; and Mr. Stephen Harvey, MBA, Chief Financial Officer, Mount Sinai Health System. The phase 1 clinical trial mentioned herein is led by independent faculty investigators (Dr. Liu and Judith A. Aberg, MD, Chief of the Division of Infectious Diseases, Mount Sinai Health System) who have no financial interests in either the vaccine or CastleVax.
About NDV-HXP-S: The NDV-based vaccine technology was developed at Icahn Mount Sinai in the laboratories of Drs. Palese, García-Sastre, Krammer, and Sun.
About CastleVax: In August 2022, the Mount Sinai Health System launched CastleVax, Inc., a clinical-stage vaccine research and development company devoted to the commercial development of the NDV vaccine platform technology.
For more information on CastleVax and the NDV vaccine platform, visit https://www.castlevax.com.
About the Icahn School of Medicine at Mount Sinai
The Icahn School of Medicine at Mount Sinai is internationally renowned for its outstanding research, educational, and clinical care programs. It is the sole academic partner for the eight member hospitals* of the Mount Sinai Health System, one of the largest academic health systems in the United States, providing care to a large and diverse patient population.
Ranked 14th nationwide in National Institutes of Health (NIH) funding and among the 99th percentile in research dollars per investigator according to the Association of American Medical Colleges, Icahn Mount Sinai has a talented, productive, and successful faculty. More than 3,000 full-time scientists, educators and clinicians work within and across 34 academic departments and 35 multidisciplinary institutes, a structure that facilitates tremendous collaboration and synergy. Our emphasis on translational research and therapeutics is evident in such diverse areas as genomics/big data, virology, neuroscience, cardiology, geriatrics, as well as gastrointestinal and liver diseases.
Icahn Mount Sinai offers highly competitive MD, PhD, and Master’s degree programs, with current enrollment of approximately 1,300 students. It has the largest graduate medical education program in the country, with more than 2,000 clinical residents and fellows training throughout the Health System. In addition, more than 550 postdoctoral research fellows are in training within the Health System.
The Icahn School of Medicine at Mount Sinai is located in New York City on the border between the Upper East Side and East Harlem and classroom teaching takes place on a campus facing Central Park. Icahn Mount Sinai’s location offers many opportunities to interact with and care for diverse communities. Learning extends well beyond the borders of our physical campus, to the eight hospitals of the Mount Sinai Health System, our academic affiliates, and globally.
About Mount Sinai Innovation Partners (MSIP)
Mount Sinai Innovation Partners (MSIP) is responsible for advancing the real-world application and commercialization of Mount Sinai discoveries and inventions, and the development of research partnerships with industry. Our aim is to translate discoveries and inventions into healthcare products and services that benefit patients and society. MSIP is accountable for the full spectrum of commercialization activities required to bring Mount Sinai inventions to life. These activities include evaluating, patenting, marketing, and licensing new technologies, building research collaborations and partnerships, coaching innovators to advance commercially relevant translational discoveries, and fostering an ecosystem of entrepreneurship within Mount Sinai and beyond. For more information, please visit https://ip.mountsinai.org
About the Mount Sinai Health System
Mount Sinai Health System is one of the nation’s leading integrated academic health systems and one of the largest in the New York metropolitan area. Its comprehensive system includes seven hospitals, more than 400 outpatient practices, over 600 research and clinical laboratories, the Icahn School of Medicine at Mount Sinai, the Graduate School of Biomedical Sciences, and the Mount Sinai Phillips School of Nursing. Together, the Health System comprises approximately 48,000 employees, more than 9,000 physicians, and 8,600 nurses.
As a leading learning health system, Mount Sinai combines clinical expertise with scientific discovery to improve patient care while training the next generation of health care and biomedical leaders. The Health System provides care across every stage of life, from prenatal care through geriatrics, while advancing personalized medicine through artificial intelligence, data science, and biomedical research.
Mount Sinai is consistently recognized among the nation’s leading academic health systems for patient care, research, and education. The Mount Sinai Hospital is ranked No. 1 in New York by Newsweek and No. 5 on the magazine’s World’s Best Hospitals list. The Icahn School of Medicine at Mount Sinai ranks No. 11 among U.S. medical schools and No. 1 among freestanding medical schools for National Institutes of Health funding, reflecting the strength of its scientific enterprise and leadership in biomedical research.
Scientists Uncover How COVID-19 Variants Outsmart the Immune System
Nov 21, 2025 View All Press Releases
