In July 2024, the US National Institutes of Health (NIH) announced the beginning of a Phase I trial to test the safety of a nasal vaccine candidate against emerging variants of SARS-CoV-2. Enrolment of healthy adults has started at three sites in across the US for the first-in-human trial of the vaccine, designed and tested in pre-clinical studies by scientists at the National Institute of Allergy and Infectious Diseases (NIAID) Laboratory of Infectious Diseases.
The vaccine enters study
The investigational vaccine, MPC/S-2P, uses murine pneumonia virus (MPV) as the vector to deliver a version of the SARS-CoV-2 spike protein (S-2P), stabilised in its prefusion conformation. MPV doesn’t cause disease in humans or non-human primates but has an “affinity for epithelial cells” along the respiratory tract, which means it could be effective in taking the vaccine to the site of natural coronavirus infection.
In pre-clinical non-human primate studies, MPV/S-2P was “safe and well tolerated”, and produced robust systemic immune responses, including SARS-CoV-2-directed antibodies, and local immunity in cells in the mucosal tissues that line the nose and respiratory tract. NIH states that studies indicate that “mucosal immunity is more effective than systemic immunity in controlling replication of respiratory viruses”.
The study is intended to enrol 60 adult participants between the ages of 18 and 64, who have previously received at least three prior doses of an FDA-approved or –authorised mRNA COVID-19 vaccine. The sites are Baylor College of Medicine, Houston, The Hope Clinic of Emory University, Decatur, Georgia, and New York University, Long Island.
Volunteers will be divided into three cohorts with participants in the first cohort receiving a dose delivered in a nasal spray at the lowest dosage. Participants in the next two cohorts will receive progressively higher doses. They will attend seven follow-up visits over a year, during which scientists will measure how well the vaccine candidate is tolerated and look for immune responses in the blood and nose.
A next-gen need
Dr Jeanne M. Marrazzo, Director of NIAID, recognised that the “rapid development of safe and effective COVID-19 vaccines was a triumph of science” and they “greatly mitigated the toll of the pandemic”.
“While first-generation COVID-19 vaccines continue to be effective at preventing severe illness, hospitalisations, and death, they are less successful at preventing infection and milder forms of disease. With the continual emergence of new virus variants, there is a critical need to develop next-generation COVID-19 vaccines, including nasal vaccines, that could reduce SARS-CoV-2 infections and transmission.”
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