The first generation of COVID-19 vaccines are being rolled out across the world in a bid to bring the pandemic under control. But in parallel a next generation of vaccines are also in development which include intranasal sprays, which hold great promise of broadening the reach of different types of vaccines.
This is because nasal vaccines boost our immune response in the mucosa of the nasopharyngeal area (the nose and throat), which is where the coronavirus first enters the body, and when people are most infectious.
The current COVID-19 vaccines have been shown to be highly safe and effective. Distributing them however comes with challenges: all of them require refrigeration, with some mRNA vaccines requiring ultra-cold refrigeration, and this can be a logistical problem in countries without adequate infrastructure, equipment or electricity supply.
Nasal spray vaccines for other diseases already exist and offer several advantages. For COVID-19 the nasal spray vaccines being tested don’t require any refrigeration, nor do they need to be given by trained health workers like injections do. Since they are designed to be used like nasal congestion sprays people would be able to self-administer them at home. The other big advantage is that they are likely to be more popular for the millions of people who don’t like needles.
STOPPING TRANSMISSION
But besides the ease of use, there’s an even more important potential advantage. It is possible that they are even better than the current injectable vaccines at stopping transmission. This is because nasal vaccines boost our immune response in the mucosa of the nasopharyngeal area (the nose and throat), which is where the coronavirus first enters the body, and when people are most infectious.
Injectable vaccines trigger a systemic immune reaction to the virus, but the nasal spray triggers mucosal immunity – this could cut the infection short just when people are most likely to spread it, and also before it has a chance to infect the rest of the body.
Such immunity might also confer an advantage against new variants as it can stimulate a broader immune response than injectable vaccines that target a specific part of the coronavirus – if the virus mutates in that target, there’s a chance the vaccine is less effective.
National Centre for Genetic Engineering and Biotechnology (BIOTEC)
Thai virologists, at the National Centre for Genetic Engineering and Biotechnology (BIOTEC), have been developing two candidate nasal spray vaccines, or vaccine inhalers, which they hope will provide an option in the prevention of COVID-19 infection, not just prevent severe symptoms.
Dr. Anan Jongkaewwattana, director of Veterinary Health Innovation and Management Research Group told Thai PBS that most COVID-19 vaccines are being administered via intramuscular injections, to stimulate antibodies in the blood stream, but not enough in the nasal passage to prevent the virus invading the body, adding that COVID-19 enters the body through respiratory system.
The first inhaled vaccine developed at BIOTEC was the Adenovirus vaccine, with financial support from the National Vaccine Institute. Two doses of the vaccine were administered to mice injected with COVID-19 and it was discovered that the mice did not die or fall sick and they ate as normal with their weight remaining stable.
The same vaccine was administered, via intramuscular injection, to other mice and the result was that none of the mice died or fell sick, but they lost weight markedly, said Dr. Anan, adding that researchers are in the process of examining virus load in the lungs of the mice.
The second vaccine being developed is to fight the influenza virus, which was weakened through gene splicing and adding the RBD protein, which produces antibodies against COVID-19, resulting in the body generating two types of antibodies against both COVID-19 and influenza.
Trials of this vaccine in mice show high levels of antibodies that prevent viral infection of the lungs.
Dr. Anan said BIOTEC will seek approval from Thailand’s Food and Drug Administration for Phases 1 and 2 of human trials of the two candidate nasal spray vaccines.
Nasal spray vaccines are not new, said Dr. Anan, adding that nasal influenza spray vaccine has been on the market since 2003, but it is not popular.
He explained that the nasal spray vaccine will produce antibodies in the mucosal lining of the nasal passage, where the virus takes root and invades the body.
Dr. Anan insisted that research and development of vaccines in Thailand is not slower than in other countries, citing the global influenza pandemic two years ago. He claimed that Thailand successfully developed the anti-influenza vaccine shortly after the US.
Source Gavi, Thai PBS World
