The novel coronavirus is an airborne respiratory pathogen that infects us through our mouths, throats, and noses. So it makes sense that a key way to prevent the coronavirus from wreaking true havoc inside of us is to stop its advance at the front gate.
That’s exactly why this week’s news that China had authorized the first-ever inhaled COVID-19 vaccine from CanSino Biologics—right on the heels of India’s emergency authorization of Bharat Biotech’s COVID-19 nasal vaccine—was heralded by the scientific community as a long-overdue breakthrough in an area of vaccine development.
Investments in these technologies, health experts say, could guard against the constant evolution of the coronavirus, prevent more people from getting infected, and address some of the weaknesses of traditional vaccine injections.
“Nasal and oral vaccines are our best shot to block infections, transmission, achieve containment of the virus, reduce the toll of sickness, & help prevent #LongCovid,” tweeted physician-scientist Eric Topol, director of Scripps Research Translational Medicine, after China’s inhaled vaccine announcement this week. “They are not getting adequate priority in the U.S.”
With injected or “intramuscular” shots, including the groundbreaking mRNA-based vaccines developed by Pfizer and Moderna, the body relies on building up immune responses by activating an arsenal of warriors such as T-cells, B-cells, and other key parts of the immune system. That has proven extremely effective at preventing hospitalization and death from COVID-19.
Where it falls short is blocking the virus before it infects our bodies and adapting to new variants and subvariants such as Omicron. That means leaving the population vulnerable to an ever-mutating virus and breakthrough infections that may still land them in the hospital.
“During the first year of the pandemic, meaningful evolution of the virus was slow-paced, without any functional consequences, but since that time, we have seen a succession of important variants of concern with increasing transmissibility and immune evasion, culminating in the Omicron lineages,” wrote Topol and Yale University School of Medicine’s Akiko Iwasaki in an overview of nasal vaccine technology published in Science Immunology. “With that, there has been a marked falloff in the capacity for vaccinations and booster shots to block infections and transmission.”
Nasal and inhaled vaccines, by contrast, could boost “mucosal immunity,” the sensitivity to invaders that can be formed in the body’s mucosal membranes, including the gut and—more relevant to COVID-19—the respiratory tract. Respiratory vaccines build up slightly different versions of the body’s pathogen-fighting T-cells and B-cells that can produce a more lasting memory of various types of pathogenic invaders.
These mucosal immune weapons can be more agile and versatile than other types, quicker to identify what should be allowed to enter the body in the first place, and which nefarious microbes should be blocked. Because of this, they may be able to stamp out the virus at an earlier stage of the infection process. Like the injected vaccines, they can also achieve a downstream immune response inside the body, meaning defenses can be built in both our respiratory passages and in our blood.
This is why scientists have long been trying to develop nasal or inhaled vaccines for the flu—another seasonal, dynamic, and endemic virus. Those attempts have run into some challenges, though, including the possibility of some serious side effects from ingredients called “adjuvants” that are often used to increase the effectiveness of vaccines. In clinical trials, the new Chinese and Indian COVID-19 vaccines were not associated with serious side effects.
Now scientists like Topol are calling for a new “Operation Warp Speed” dedicated to a long-term focus on these types of vaccines that prevent infection and transmission at an earlier stage.
It’s still unclear whether the new vaccines from India and China will meet the evolving challenge of the coronavirus. But their milestone efforts, much like the once-dismissed science of mRNA vaccines, could certainly prove a springboard for the future.