A little over a year after the emergence of COVID-19, scientists found a way to fight it with mRNA vaccines from Pfizer/BioNTech, Moderna, and other firms. Studies showed that these vaccines work against the initial strains of COVID-19, and the jabs are still effective in cutting down severe illnesses and hospitalizations.
However, many of us aren’t comfortable with needles. For those, an inhalable version of the COVID-19 vaccine may soon be available. Scientists say that nasal sprays could become the next generation of COVID-19 vaccines and provide even more protection against the dangerous virus. In fact, new research has shown that intranasal vaccines can help provide protection from Omicron and its many subvariants – something mRNA vaccines haven’t quite been able to do.
In a new study published in the journal Science Immunology, researchers from the University of Virginia (UVA) analyzed the foundering immune response in the airways of people with COVID-19 vaccinations compared to those with natural protection after infection. They note that intranasal vaccines for COVID-19 will be essential to protect people against the emerging variants of concern of the SARS-CoV-2 virus.
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“The omicron variant almost completely escaped neutralization by mucosal antibodies in individuals who received mRNA vaccines and in previously infected individuals,” said Jie Sun, professor of medicine at UVA. “Our data showed that mRNA vaccination also did not induce sufficient tissue-residing cellular immunity in the airways, another arm of our immune system to prevent the entry of the virus into our bodies.”
The mRNA vaccines like Pfizer, Moderna, and others take inspiration from messenger ribonucleic acid, the delivery system that drives biological reproduction. In the study, the researchers explained that the mRNA in these vaccines is not derived from a live virus but is instead synthesized in a lab to look like an invader. This is enough for the body to recognize the real virus in the future - they say.
The researchers further noted that bloodstreams get strongly boosted by the mRNA vaccine while the mucosal lining – the moist, inner lining of some organs – experiences moderate or little neutralizing antibody response. They found that only the bodies of unvaccinated patients who were seriously ill were able to fight against the virus in both their airways and their bloodstreams.
Meanwhile, mice that were administered a nasally delivered vaccine stemming from adenovirus – a group of common viruses that expresses the spike protein found in COVID – showed “robust neutralizing antibody responses” in combination with mRNA vaccine shots.
The team states that the nasal vaccine provides a mucosal antigen boost to the pre-existing memory of T and B cells that direct the immune response. This results in higher cellular and humoral immunity. Importantly, the immune response was effective both against the ancestral virus and the Omicron variant.
The uptick was found as an improvement over the bloodstream's normal vaccinated response, as well as in the bronchi of the lungs.
Scientists have been working on COVID-19 nasal vaccines for the past couple of years, but none have been approved for use so far. Leading experts believe that these inhalable vaccines do hold promise. Nasal vaccines induce antibody production just like traditional vaccines, but they do so in the mucosal tissue where the virus typically enters the body. Immunologists say that we need mucosal immune responses to get effective protection against infection, and this is where nasal vaccines have the advantage.
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Currently, an “inhaled aerosol” version that targets the lungs and upper airways is in Phase I clinical trial. This vaccine candidate was developed by a team of scientists from McMaster University. However, adenovirus-based nasal vaccines are different and haven’t been approved for humans yet, primarily out of concerns about harmful side effects.
The research team says that they now need a step-up trial from a mouse to a human study in the US. “A human trial has been performed in China already using nasal adenovirus spray, which suggests it is generally safe and can boost good immune responses, but mucosal immunity was not examined," Sun added.
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