COVID-19

We explain everything about the mucosal vaccine, this hope of ending the Covid

COVID – This is a serious clue. The Covid-19 pandemic has seen messenger RNA vaccine technology (those from Pfizer and Moderna laboratories, in particular) develop at a breakneck rate, never approved for humans until then. However, there is another vaccine method not yet exploited in the fight against the epidemic: that of the mucosal vaccine.

Emeritus Director of Research at Inserm, Cecil Czerkinsky is a specialist. Interviewed by LeHuffPost, the immunologist explains that “these are formulations that are administered mainly through the nose or orally”, often in the form of a spray, that is, without a sting.

The function of this vaccine is to strengthen the immunity of the mucous membranes, in particular that of the upper respiratory tract (nasal and oral), and ideally the lung. To understand the value of this vaccine technology, one must begin by distinguishing the immune system of the mucous membranes from the general immune system, also called systemic. “There is an autonomous mucosal system, which works practically independently of the systemic immune system, that is, of the blood or the lymph nodes, for example. The latter is the one that is stimulated with injectable vaccines ”, summarizes the researcher.

At the moment, there are few vaccines for the mucous membranes; They are primarily intended to prevent intestinal infections. Among the best known, we find the vaccine against polio, typhoid fever or cholera. Currently, several teams are working around the world in their development against Covid-19.

Lock the front door

If the mucosal vaccine is interesting in the fight against the SARS-COV 2 pandemic, it is because it could prevent contamination. Because as we said earlier, these vaccines strengthen the immunity of the mucous membranes of the mouth and nose. However, these are precisely the main entry gates for the virus into our body. “The mechanism of injectable vaccines operates in the pulmonary mucosa, but little or nothing in the oral or nasopharyngeal mucosa,” says Inserm’s research director.

The injectable vaccines currently in use prevent the virus from replicating in the deep mucous membranes and therefore contain severe forms of the disease. On the other hand, this provided immunity is not concentrated in the mouth and nose. “This is the reason why the infection of many vaccinated only affects the mucous membranes of the upper air,” he adds. It is this lack of immunity that explains, for example, contamination or loss of taste in vaccinated people.

Mucosal vaccines in development aim to develop nasal, oral, and ideally pulmonary immunity. In any case, it would therefore be added to the injectable vaccines already present, to reinforce the immunity of the individual.

Vaccine complementarity

The combination of the two vaccines would allow a strong systemic response and a strong mucosal response. “We must start with a mucous membrane vaccine, then proceed with a parenteral booster, by injection, but not the other way around,” warns the vaccinologist.

Clearly, the idea is to educate the mucous system first and then do systemic reminders to have both types of responses. In recent years, combinations of injectable and mucosal vaccines have been studied, and this is what Cecil Czerkinsky recommends for Covid-19.

“That’s what is going to speed things up, the combination. The development of a mucosal vaccine over an existing parenteral vaccine, and there are many options, will be faster. If a study shows superior protection of a mucoso-parenteral individual compared to a single parenteral individual, that will help things. ”

An Israeli study published in August 2021 also points in this direction. This shows that a person who has been infected and therefore immunized through the mucosa and then vaccinated by injection will produce a very strong mucosal and systemic response. Whereas a person who has received two doses without having contracted the virus will only have systemic immunity.

Therefore, the mucosal vaccine could provide part of the immunity provided by the infection. Furthermore, it is likely to be effective against the variants, because mucosal antibodies have a broader spectrum of recognition than systemic ones. But this is still a hypothesis, it has yet to be proven.

A mucosal vaccine in 2022?

A Yale team is working precisely in this field of exploration. And it is not the only one: in Sweden, the United States, France, England and even in China, scientists are trying to develop this vaccine. Among the 130 candidate vaccines listed by WHO, there are about ten mucosal vaccines.

“It’s a big crowd, but nothing compared to those working on the injectable vaccine,” says Cecil Czerkinsky. Especially since these candidates must respond to a formulation problem, which is much more complicated than that of injectable vaccines. “The challenge is to get the mucous membrane vaccine, which is in the form of a spray or emulsion, to cross the natural barriers of the mucosa. They are extremely powerful and fortunately for us elsewhere. “

In contrast, injectable vaccines do not face this type of unfavorable environment, since the needle allows to force the barriers of the epidermis and the dermis. Once the correct formulation is found, clinical trials should go to phase 3, then comes the question of production.

“It has to be able to meet the demand. We are talking about hundreds of millions of doses. In addition, doses higher than those of injectable vaccines are generally required and, therefore, a higher production capacity. We are far from that ”, warns the specialist. ″ That does not mean that it cannot arrive quickly, since everything happened quickly. But considering the current state of research, I don’t think that a mucosal vaccine will see the light during the year 2022. Instead, in 2 years, this is possible ”, hopes Cecil Czerkinsky.

At the same time, other avenues are also being explored, notably anti-Covid pills. In mid-December, Pfizer also confirmed very positive results from its antiviral treatment. According to clinical trials, Paxlovid reduces hospitalizations and deaths in people at risk by almost 90% when taken in the first few days after symptoms appear.

See also The HuffPost: Are we going to multiply withdrawals against Covid-19?

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