A novel inhalable influenza vaccine candidate appears to be safe and could enhance protection against seasonal and pandemic influenza for individuals at high risk of severe illness, especially when combined with the yearly flu vaccine.
A novel inhaled influenza vaccine candidate, developed by researchers at the University of Wisconsin-Madison, has shown safety and potential to improve protection against both seasonal and pandemic flu in individuals who are more susceptible to severe illness, particularly when used alongside the routine annual flu shot.
The results come from a randomized, controlled trial conducted in 2022, where the vaccine was given in nasal spray form along with the annual flu shot to participants aged between 65 and 85 years. These findings were recently published in the journal Lancet Infectious Diseases. Here are the details:
An innovative approach to influenza vaccination
The vaccine candidate examined in this trial, known as FluGen’s M2SR, is derived from technologies innovated by UW-Madison researchers Yoshihiro Kawaoka and Gabriele Neumann over ten years ago. It stands out from traditional seasonal flu vaccines, which often provide inadequate protection against severe disease for at-risk populations:
- Standard flu vaccines use inactivated influenza virus delivered via an injection into the muscle, prompting the immune system to create antibodies against the virus.
- In contrast, the M2SR vaccine involves a live virus with an essential replication gene removed, administered through a nasal spray directly to the upper respiratory tract.
- This gene deletion ensures that “it cannot replicate and cause illness, yet it activates the immune system similarly to a natural infection,” explains Pamuk Bilsel, who led the study as the chief scientific officer for FluGen, a company co-founded by Kawaoka, Neumann, and FluGen CEO Paul Radspinner.
Promising safety results from the study
In 2022, FluGen evaluated the safety and immune responses of the candidate vaccine among over 300 individuals in the U.S. aged 65 to 85.
- Some participants received only the annual flu shot designed for their age group, while others were given just the nasal spray vaccine. A third group received both vaccines, and a fourth group got the regular shot alongside a nasal spray placebo.
- Participants who received the nasal spray candidate reported good tolerance, with only a few experiencing mild side effects like a runny nose and nasal congestion.
- Blood tests and nasal swabs taken one day after vaccination and again 2-4 weeks later indicated that those who received both the nasal spray and flu shot developed significantly higher levels of protective antibodies and other immune responses compared to participants who only had the flu shot.
- According to Bilsel, these participants gained not just the typical antibodies from the ordinary flu shot but also local immunity, mucosal immunity, and T-cell responses, resulting in “a comprehensive and robust immune response.”
Enhanced protection against seasonal flu and potential pandemics
While the primary focus of the study was on the safety of the vaccine candidate, the immune response data suggest that older adults would benefit from a combination of the flu shot and the nasal spray vaccine for better protection against influenza.
- The more robust immune response gained from using both vaccines might protect against seasonal influenza and emerging pandemic strains, particularly in the case of threats like the circulating H5N1 avian influenza if it became easily transmissible among humans.
- Although the vaccine candidate appears promising, larger trials are on the horizon to confirm its safety and effectiveness, with a completion timeline of a few years.
“Older adults deserve superior options for preventing flu-related infections, illnesses, and hospitalizations, and we believe we are on the right path,” says Radspinner. “We hope that existing vaccine manufacturers will recognize this potential and collaborate with us to bring this solution to patients sooner rather than later.”
