Nasal spray Covid-19 vaccines would be more effective than injectable vaccines

Scientists are hoping to generate superior immune responses with inhaled vaccines that directly target the airway cells the virus invades.

An alternative to conventional jabs, sprayed and inhaled immunizations under development in the U.S., Britain and Hong Kong could play an important role in helping society escape restrictions that have upended economies and everyday life.

Among their goals is to prevent the pathogen from growing in the nose, a point from which it can spread to the rest of the body, and to other people.

“Local immunity matters,” said Frances Lund, a University of Alabama at Birmingham immunologist working with biotech Altimmune Inc. on an early-stage nasal inoculation. “The vaccines that can be delivered to generate that will have some advantages over vaccines that are delivered systemically.”

Most early vaccine developers focused on a familiar route – injections – seen as the fastest to protecting the world from disease. Inhaled vaccine makers are counting on some of the unique features of the lungs, nose and throat, which are lined with mucosa. This tissue contains high levels of immune proteins, called IgA, that give better protection against respiratory viruses.

Activating these immune weapons, they theorize, can protect areas deeper in the lungs where the SARS-CoV-2 does the most damage. They also may improve vaccines’ chances of blocking transmission.

“The first generation of vaccines are probably going to protect a lot of people,” said Michael Diamond, an infectious disease specialist at Washington University in St. Louis. “But I think it’s the second- and third-generation vaccines – and maybe intranasal vaccines will be a key component of this – that ultimately are going to be necessary. Otherwise, we’ll continue to have community transmission.”

In a study of mice in August, Diamond and his team found that delivering an experimental vaccine via the nose created a strong immune response throughout the body; the approach was especially effective in the nose and respiratory tract, preventing infection from taking hold.

Vaccines that are sprayed into the nose or inhaled may hold other practical benefits. They don’t require needles, may not need to be stored and shipped at low temperatures and can reduce the need for health workers to administer them.

“When you’re thinking about trying to deliver that across the world, if you don’t need to have an injectable vaccine, your compliance goes up because people don’t like getting shots,” according to Lund, the Alabama-based researcher. “But secondly, the level of expertise needed to administer that vaccine is significantly different.”

Imperial researchers point to evidence that delivering influenza vaccines via a nasal spray can protect people against illness and help reduce transmission; they’re keen to explore if that’s also the case for SARS-CoV-2.