There are advantages to delivering vaccines through the nose compared to via intramuscular injections particularly when it comes to diseases transmitted through the respiratory system. Yet in the rush to save the world from COVID-19, few institutions focused on intranasal delivery, and outcomes have lagged far behind. Nevertheless, one intranasal vaccine has now demonstrated success in preclinical trials, opening the possibility of an alternative approach that might eventually help rid the world of this scourge.
The journal iScience reports two doses of an intranasal vaccine developed at Lancaster University gave hamsters complete protection against lung infection and inflammation from several SARS-CoV-2 variants. The same vaccine had previously been shown to be safe and produce an encouraging immune response in mice, without testing its protection levels for them.
Existing vaccines give similar results on those accounts. Where the nose may have an advantage is in reducing the shedding of the virus from the nose and lungs. This would greatly reduce the chances that people who do get infected with COVID-19 would pass it on.
“After we administered the vaccine into the noses of hamsters and then infected them with SARS-CoV-2, we found almost no virus replication in the lungs and nasal wash of these animals.” Dr Muhammad Munir said in a statement.
Existing vaccines already provide significant protection to those around the vaccinated person, since you can't pass on a virus without getting infected. Even those who do suffer a “breakthrough” infection are probably less likely to transmit the disease on than if they hadn't been vaccinated in the first place, but the extent of this is uncertain. The Lancaster trials, run jointly with the Texas Biomedical Research Institute, raise the possibility intranasal vaccines could do a better job of preventing transmission, provided the results can be replicated in humans.
In addition to the potential to reduce transmission by those who are infected, intranasal vaccines could overcome vaccine hesitancy. A large part of the reason we are so close to eliminating polio, while other diseases have proven harder to overcome, is that people prefer to consume medication orally than have a needle stuck in their arm. Spraying a vaccine up your nose may not be as enticing as eating a syrup-laced sugar cube, but it's a step.
Intranasal vaccines may be slower to develop, but they should be easier to produce and distribute, being less in need of refrigeration. This particular vaccine can be produced in eggs, like the annual flu shot. “We are excited by the scalability of this nasal vaccine which we hope will contribute to reducing vaccine inequity, allowing equal access to vaccination globally. Nasal delivery is also a more appealing delivery route for use in children,” said co-author Dr Lucy Jackson-Jones.
The vaccine uses an engineered Newcastle Disease Virus (NDV) to produce SARS-CoV-2 spike proteins to prime the immune system to recognize SARS-CoV-2's method of cell entry. NDV is an avian disease whose virus can replicate, but causes only mild symptoms in humans, unlike chickens.
The time-consuming nature of clinical trials means the intranasal vaccine will not be available until well into next year at the absolute earliest. Tragically, it is likely it will still be needed then.