To verify the efficacy and safety of experimental vaccines against the emerging corona virus, researchers conduct clinical trials on tens of thousands of volunteers, generally distributed equally among two groups. One of them is receiving a placebo ... This is the case with the experiments on the vaccines "Pfizer - Biontech" and "Moderna", which their developers attributed to them are very high efficacy, according to Agence France-Presse.

The experiment is being conducted in the United States exclusively on 300 thousand volunteers, and the placebo treatment does not exceed a saline solution without any therapeutic effect.

The volunteers participating in the research continue their lives normally: after receiving the injection, they return home and continue to work or study like others, with the need to follow the same preventive measures, both in terms of home quarantine, and the need to put a muzzle.

Over the days, a number of participants will naturally be infected with "Covid 19", which will inevitably be known; Participants must regularly inform researchers of any symptoms they have, and any suspected case is subject to diagnosis.

If the vaccine is effective, the number of cases recorded among participants who actually received a vaccine will be less than that recorded in the second group whose members received a placebo vaccine.

The goal is to record a difference large enough to exclude the chance hypothesis in these results. Researchers resort to statistical methods to reach a predetermined minimum of certainty.

Reaching an efficacy rate of 100% means that no case was recorded among people who actually received the vaccine, and several cases were in the second group.

The first goal of vaccinations is not to prevent the transmission of Coronavirus infection, but rather to prevent people from contracting “Covid 19” disease caused by the virus. The vaccine is classified as highly effective if it succeeds in preventing "Covid 19" infections in its dangerous forms.

This research stems from the idea that if a vaccine succeeds in protecting people from disease, then this means achieving the desired goal in terms of public health, even with the continued registration of people with the virus without any symptoms.

The researchers only record whether there is a difference "in real life" in terms of rates of "Covid 19" infection between people who received the vaccine and those who did not receive it.

In the absence of a 100 percent effective treatment, it would be unethical to intentionally expose people to contracting the Coronavirus, although researchers have already suggested doing so with healthy young people.

But the real problem is that we need two to more years for the duration of protection that the vaccine will provide to those who use it, and whether or not side effects will appear in the long term on the patient. At the time of writing these lines, no health company has issued a response to these questions, and we are still waiting for recommendations from health organizations to solve this problem.