In this new phase of the pandemic, the effectiveness of the administered vaccines is analyzed and the need for booster doses for the most vulnerable people is debated.
At the same time, the investigating to go one step further in the fight against covid-19. Avoiding the transmission of the virus with new vaccines, or reducing it more than the current ones, would reduce infections and bring the final blow to the coronavirus closer.
One of the most effective defenses is usually to attack where it hurts the most, avoiding from the beginning the reproduction in the upper respiratory tract.
Therefore, the development of nasal vaccines becomes a route of administration with many advantages.
As mentioned previously, the localized action of a nasal vaccine would allow, in addition to the development of systemic defenses (totals), prevent the reproduction of the virus from the beginning of contagion.
To be administered through the nasal route , vaccines must comply with exhaustive controls, due to the direct contact between the nasopharyngeal cavity and the central nervous system through the olfactory and trigeminal nerves. The blood-brain barrier is an effective protection against pathogenic substances and agents.
It is necessary to cross it for targeted therapies, for example, when treating neurodegenerative diseases and migraines. Small molecules do it, but you have to prevent what is not necessary from passing through it. If they are vaccines and they are large in size, it would be enough, but it must be controlled.
- Two decisive advances in the next vaccines against the covid to try to put an end to the pandemic
For this reason this type of administration entails extra work.
Vaccines called “sterilizing” generate immunity right where the virus enters: the mucous membranes of the nose . We review five of them, which employ different approaches to this difficult task.
one. The Mexican vaccine “Patria”
The most advanced is being developed in Mexico and has already passed phase I clinical trials.
It is based on a recombinant virus expressing the SARS-CoV-2 spike protein. The production method is the traditional one with which the flu vaccine is produced, with embryonated eggs.
The vaccine has been safe and generates immunity when administered intramuscularly, and even better when a first dose is administered nasally and a second intramuscularly.
- Do you already know our YouTube channel? Subscribe!
The other vaccines are still finishing preclinical studies in animals.
2. The Spanish vaccine of Luis Enjuanes
The second of the vaccines is being developed in Spain in the Laboratory of Luis Enjuanes (CNB-CSIC). It is conducting studies in macaques after successfully completing the studies in mice.
This is a synthetic emulation of the SARS-CoV-2 virus that it lacks the parts that give it pathogenicity, and it is being tested with intramuscular and nasal administration.
3. The French vaccine that protects the lungs
It has been developed at the Pasteur Institute in France and is proposed as a reinforcement of the intramuscular vaccine. It is a nasal vaccine based on a lentiviral vector that expresses the spike protein of the delta variant of SARS-CoV-2.
Se has been administered in mice after two intramuscular doses of an RNA vaccine.
The results are very promising, observing great protection at the mucosal level via IgA (the specific antibodies of the mucosa) and at the lung via resident memory B and T cells.
4. The vaccine against all sarbecoviruses
The fourth, developed at the University of Yale in the USA, consists of a nasal spray containing the spicule protein and is administered following an intramuscular vaccine.
As in the French study, IgA is generated in the mucous membranes and resident B and T cells in the lungs in mice. The difference is that no adjuvant or viral vector is needed and, in addition, it produces general immunity against any sarbecovirus (the family to which SARS-CoV-2 belongs).
5. The Texas vaccine
The fifth vaccine is being developed at the University of Houston, USA ., and consists of a nasal spray containing the SARS-CoV-2 spike protein and an adjuvant.
Like the two previous ones, it results in protection at the level of mucous membranes and lungs in mice.
In addition to these vaccines, there are many others that are already in the clinical phase (Table 1) using different platforms, such as adenovirus or attenuated virus. Administration routes other than the nasal route are also being studied, such as the subcutaneous or oral route.
With so many candidates, we hope that there will soon be several approved nasal vaccines and we can think not only about reducing hospitalizations and deaths, but in eradicating the virus.
As already it was done at the time with smallpox, or it has almost been done with poliomyelitis. In this way we will end the dance of variations and waves that prevent us from planning our lives months in advance.
*Matilde Cañelles López is a scientific researcher. Science, Technology and Society, Institute of Philosophy (IFS-CSIC), María Mercedes Jiménez Sarmiento is a scientist at the CSIC. Systems biochemistry of bacterial division. Scientific communicator, Margarita Salas Biological Research Center (CIB – CSIC) and Nuria Eugenia Campillo is tenured scientist. Medicinal Chemistry, Margarita Salas Biological Research Center (CIB – CSIC)
*This itemicle was posted on The Conversation and plays here í under the Creative Commons license.
Click here to read the original version.
Remember that you can receive notifications from BBC Mundo. Download the new version of our app and activate it so you don’t miss our best content.