Spurred by the pandemic, scientists are studying the benefits of intranasal vaccines and what makes them more potent than shots in the arm.
The current batch of Covid-19 vaccines effectively prevents severe disease and death and offers substantial protection against the variants. But the authorized vaccines are not 100 percent effective at blocking all infections. To address this deficit, scientists are exploring new ways of delivering vaccines that yield stronger and more durable immunity against SARS-CoV-2.
One promising approach might be to trade a jab in the arm for a spritz up the nose. Over the past several months, as some manufacturers are preparing booster shots to deliver a third dose, a handful of promising studies have revealed the effectiveness of intranasal vaccines in mice, ferrets, hamsters, and non-human primates.
Further along are six candidate Covid-19 vaccines, administered as nasal sprays, that are currently in phase 1 clinical trials. And, just this week, at the meeting of the American Society for Virology, Meissa Vaccines announced that a single dose of their intranasal vaccine candidate showed promising results in non-human primates. If these vaccines come to market, immunologists say that might offer better protection because they more closely resemble the way the virus naturally infects us - through the mucous membranes of the nose and upper airways. And immunologists say this makes a difference in the immune response.
“If you want to generate a sustainable, long-lasting immune response, you want to vaccinate locally,” says José Ordovas-Montañes, a Harvard University immunologist who studies immunity in the gut and nasal mucosal tissues. Ordovas-Montañes says that when we get a jab in the arm, we are inducing immunity on a systemic, body-wide scale where our antibodies and T cells will distribute themselves around the blood vessels. While that might sound good, this approach is “sub-optimal” because the immune cells are “distracted” and not focused on the location where the virus enters the body.
A shot up the nose, on the other hand, provides a big boost of immunity in the upper respiratory tract and potentially the lungs, eliciting a local antibody response and T cell response. This enables immune cells to apprehend and destroy the pathogen on arrival.