Why no coronavirus vaccine has ever been found

CORONAVIRUS – The road to a vaccine is full of pitfalls. Whatever the virus against which a treatment is sought, there is a long way to go, marked by a series of tests in laboratories, then in clinics, before going into production. Treatment for coronavirus, like polio or flu, is no exception to this obstacle course.

But SARS-CoV-2, responsible for a global pandemic and quarantine like no man had ever seen, is not quite a customer like any other. While he is the center of attention today, researchers and the health sector know his family well, that of the coronavirus, which includes four types of virus. However, so far, no vaccine has been found: as you can find out in the videoat the top of this articlefinding the flaw in the coronavirus is a particularly daunting task.

There are indeed many gray areas around this family of organisms, and more particularly those responsible for the respiratory infections that we know: SARS, whose epidemic in 2002-2004 had caused several hundred dead in China, then MERS, which declared itself in the Middle East in 2012. “The problem”, summarizes Morgane Bomsel, specialist in virology at the Cochin Institute, “is that does not know enough virus to understand the problems it poses. ” Hence a research effort in a dispersed order.

A known but elusive virus

Whether it’s SARS-coV-2 or its cousins, coronaviruses are on the move. Arrived by the respiratory tract, they migrate in severe cases towards the lungs, where their multiplication is at the origin of fearsome pneumonias. But that’s not all: studies have found in some cases that the virus has colonized the heart, or the brain, causing other symptoms.

The question of which type of immunity is most effective is therefore central. Should vital organs be protected? This will require a vaccine formula that can react to T lymphocytes in the lungs against Covid-19 infection.

Should we rather look for a local response of the respiratory mucosa, to prevent the virus from spreading? Cellular immunity must then be targeted with another combination. It has only been in recent weeks that we have started to have more precise data on the angle of attack to adopt in the face of this multi-weapon virus.

Likewise, coronaviruses induce a particularly unpleasant reaction for epidemiologists. While antibodies are created by our body to treat it, many studies have noted in patients the arrival of so-called “facilitating” antibodies. The latter, created after a first infection, have the annoying habit of opening the doors of cells to the virus, even when they are supposed to defend them.

This mechanism, which we have already seen working with dengue patients, is a headache in the development of a vaccine. Only long-term experience can correctly define an antigen that does not endanger the patient even more in the event of a new epidemic. “We know there is a facilitative response with SARS and MERS,” says Morgane Bomsel. For Sars-cov-2, “it may be necessary to go through another route of immunization” if the tests confirm the facilitating antibodies.

Our protection from Covid-19 thus raises more than one question, as the successive declarations of the World Health Organization have shown. The WHO first warned that being infected and then cured of the virus did not mean that one was immune … before, a few days later, to affirm that this time there was no longer any doubt . Despite these reassuring words, there is insufficient data to know with certainty how long our body, after an illness or a vaccine, effectively produces antibodies capable of defending us against infection. This is essential in the development of a vaccine and the type of response it should elicit.

Promising studies, but no hindsight

Finally, it is the nature of the vaccine itself that could constitute an additional obstacle to this solution. One of the most promising candidates is indeed a messenger RNA vaccine, a completely new type of injection. Unlike the prophylactic vaccine, it is about sending an RNA sequence that “dictates” to our cells to build antigens, which in turn stimulate our body’s immune response.

This modern solution is extremely exciting, even more than DNA vaccines. But there is a problem: so far, there is no messenger RNA vaccine on the market, none of which has shown sufficient efficacy. If the latter proved to be the best candidate at the end of phase III testing, a whole production chain would still have to be invented and brought out of the ground.

The RNA vaccine uses components very different from its predecessor. It will be necessary to be able to produce industrially a product considered in the review Nature like the “cream of the crop” in biotechnology. “This is a new approach, of which there is currently no proof that it works,” tempers Morgane Bomsel. As with the other stages on the road to the vaccine, “we lack perspective”, she says.

All these obstacles still standing in the way of an effective treatment for coronaviruses, and today still sars-cov-2, can therefore be roughly summed up in two factors: time and investment. Previous acute respiratory syndromes were successfully combated before a vaccine was found, and research was halted.

Now, the opposite problem arises: the search for a vaccine is in full swing, but there is not enough time to carry out the preliminary studies which normally allow better knowledge of the virus, in order to fight it as effectively as possible. Pandemic requires, funding is not lacking, unlike previous episodes. The result is a frantic race where all the methods are tested in parallel by laboratories around the world, with as roadmap these obstacles to overcome.

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