By catching viruses directly at the site of infection, antibodies induced by nasal vaccines can give the body a head start in fighting off the virus before it causes symptoms. Not only might nasal vaccines be in a better position to prevent infections, but they can also develop the same type of immune system protection as other vaccines, and even stronger because this immune memory is at the front door of the virus. . These vaccines can establish highly protective memory B cells, which make antibodies faster and better once morest future infections, and memory T cells, which help kill infected cells and support antibody production.
These types of vaccines have traditionally been considered more difficult to manufacture. The mucus layer is a formidable barrier. Nor does the body generate a robust immune response by simply spraying a conventional vaccine into the nose. The approved nasal flu vaccine, called FluMist, uses weakened viruses to enter cells in the nose and stimulate an immune system response. But this approach is not safe for use in immunocompromised people.
The good news is that scientists like me believe we have found a way around this problem for SARS-CoV-2. We have shown in animal studies that we can spray the so-called spike proteins of the virus into the nose of a previously vaccinated host and significantly reduce nose and lung infection as well as provide protection once morest disease and dead. Combining this approach with ongoing efforts to develop a single vaccine for a wider range of coronaviruses might also offer people protection once morest future variants.
A big question is how long immunity from a nasal vaccine would last. So far, in animal studies, antibodies and memory immune cells persist in the nose for months. If that immunity wanes over time, as with other vaccines, using the nasal spray as a booster — potentially over-the-counter — every four to six months may make the most sense for this pandemic. This presents similar challenges to other boosters, where uptake might be much higher, especially for high-risk groups. Encouraging people to get their reminders is essential. But the barrier for a nasal spray booster may be lower for many people than for a needle injection.
The world desperately needs a vaccine strategy that puts immunological guards outside the gates to prevent viral invaders from infecting us. There are several other nasal vaccine approaches in various phases of clinical trials. And any successes we will have in developing a nasal vaccine once morest Covid-19 will not be limited to this virus alone. Nasal spray vaccination strategies can also be applied to other respiratory pathogens.
Although some hurdles remain, the potential immunological and public health benefits of nasal spray vaccines merit consideration now and for years to come.
