What is Phase III of the development of a coronavirus vaccine and how are side effects detected?

Coronavirus vaccine: here are the steps it will need to go through ...

In recent months, as the news about the coronavirus vaccine has been pouring in, concepts such as 'Phase I, II and III', 'pharmacovigilance', or 'randomized clinical trial' have crept into the public conversation. As I write these lines, in fact, not only is it being discussed whether Russia has the "first coronavirus vaccine", but numerous vaccines are starting Phase III of their respective clinical trials. In other words, they are on the verge of becoming a reality in pharmacies, hospitals, and health centers around the world.

And yet, as a reflection of the central importance that clinical trials have acquired in recent decades, the doubts and feelings found around the 'race for the vaccine' are also beginning to become general. It is logical. Although we can find pioneers who applied the scientific method to the search for drugs brilliantly, in the modern world advances around drug safety are often bastard children of medical tragedies.

How do we avoid the next tragedy?If we want to understand the birth of the now famous phases of clinical trials we have to travel to the second half of the 20th century. In 1962, when the tragedy of thalidomide, a popular anti-pregnancy nausea drug that turned out to be teratogenic (produced birth defects in fetuses), led to the passage of a series of regulations that forever changed the way research was conducted. in biomedicine.

As the cases accumulated, it became clear that at Grünenthal, the company that discovered it, no one had thought it a good idea to do studies with pregnant women before marketing it (not even with pregnant animals). As the victims piled up in the delivery rooms and the affected platforms mobilized against the company, public opinion began to call for measures to prevent the next tragedy.

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In the United States, a legislative package was passed that introduced public oversight and informed consent in clinical trials. It was 1962 and in the following years, the Declaration of Helsinki of the World Medical Association of 64 and the International Covenant on Civil and Political Rights of the UN in 66 established the importance of drug safety and medical ethics at the international level.

Studies, phases, and authorizationsOver the years and the increasing ethical and technical demands, biomedical research has had to confront again and again the question that heads this section: how do we avoid the next tragedy? By dint of trial and error, today we have a framework that forces companies and researchers to answer the necessary questions with an adequate level of certainty. This is where the phases of the clinical trial are born and acquire their meaning. This is how medicines and vaccines are tested.

Before reaching human trials, every drug or vaccine has to undergo a series of studies that we usually call 'preclinical'. Whether in vitro (in the laboratory) or in vivo (with animal models), these studies attempt to extract preliminary data on efficacy, toxicity, and pharmacokinetics. In other words, they are the preliminary studies that help us decide if a specific molecule is promising enough to start the whole 'clinical' process.

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Phases 0, I and IIGoing to human testing is not an easy decision. Clinical trials are usually very expensive, and most of them go nowhere. For this reason, in recent years the so-called "Phase 0" has become popular. These are small human trials in which, using doses of the drug or vaccine at subclinical levels, researchers try to get a more realistic perspective on what the drug does in the body of those who consume it. Either way, with 'Phase 0' or without it, if the researchers believe that the drug has possibilities and the numbers support it, 'Phase I' would start.

The 'Phase I' are trials that seek to assess the safety profile of the drug. In general, they involve small groups of people (between 20 and 100 patients) and try to rule out adverse effects derived from the use of the drug. To do this, the researchers closely monitor the participants: they carefully collect their experience, study the possible symptoms they report and carry out constant analyzes (lately even genetic) to find complications. If you pass this phase and, under normal conditions, up to 70% of the drugs exceed it, Phase II begins.

The big question about side effects: Without a doubt, the big question to answer during the testing process of a drug or vaccine is that of side effects. After all, the desired effects, the exact dosages, or their comparative efficacy are things to look forward to. Side effects, no. We can never be sure that we are not missing anything. Without going any further, last year we were discussing the possible side effects of one of the most used drugs in the world. In these phases, above all, it is a question of ruling out serious effects

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Its main objective is to evaluate its effectiveness (and it is about discovering which dose works best); in the case of vaccines, their ability to generate antibodies and how many doses will be necessary. For this, they are usually divided into two sub-phases: the first would focus on demonstrating the clinical efficacy of the product and the second on determining the ideal dose to face Phase III. Under normal conditions, only a third of drugs that reach Phase II exceed it. 

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