A Nasal Spray Vaccine Could Be Key to Stopping the Spread of Covid-19
It would provide a first-line defense against the virus
Covid-19 vaccines are incredibly good at preventing severe symptoms and hospitalization, but they’re probably less effective at stopping transmission. To do that, we might need a different kind of vaccine altogether.
Because SARS-CoV-2 is mainly transmitted through droplets and airborne aerosols, some scientists reason that a vaccine should provide first-line protection where the virus typically enters the body — the nose. A Covid-19 vaccine that’s sprayed into the nose may not only prevent people from getting sick in the first place but also stop them from spreading the virus to others.
“When you get Covid-19, you don’t get injected with the virus. You get it in your respiratory tract,” Matt Memoli, MD, a virologist at the National Institute of Allergy and Infectious Diseases, tells the Coronavirus Blog. “So, you don’t need antibodies in the blood to prevent infection there. You need antibodies at the site of infection at the mucus membranes, at the airways.”
All vaccines are designed to spur the production of protective immune proteins called antibodies. Most vaccines are injected into the muscle, which stimulates serum antibodies that circulate in the blood. Serum antibodies are generally very effective at protecting against serious disease.
A nasal spray vaccine, on the other hand, generates antibodies that are secreted by the tissue that lines the inside of the nose. Antibodies here can block the incoming pathogen at the site of infection. This type of immunity is known as mucosal immunity. FluMist, a nasal spray vaccine for flu, works this way.
Without protective antibodies in the nose, those who get an injected Covid-19 vaccine can harbor viral particles there even if they don’t have disease symptoms themselves. That means it’s still possible for people to pass on the virus even if they’re vaccinated.
The authorized Covid-19 vaccines by Moderna, Pfizer, and Johnson & Johnson aren’t designed to generate mucosal immunity, but there’s some indication that they do. Early data shows that they can reduce asymptomatic cases, which means they provide some level of…