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Why is it wrong to compare the efficacy of the vaccines? Dimas Covas and researcher from Project S, responds

Publicado em: 01/01/1970

With the SARS-CoV-2 virus spreading in a very short time all over the world, the need  of testing and producing different vaccines has become fundamental to the fight against the pandemics of the Covid-19. With a higher offer of vaccines, as each one of them was produced with a different technology and performance during the clinical trials, it became a habit of comparing the efficacy, judging that one vaccine is better than the other. But the scientists alert: it is a mistake.

Each vaccine have methodological and technological different bases, and its clinical trials take on account the specific singularities that can not be compared, explained the president of Institute Butantan, Dimas Covas, during the CoronaVac Symposium, which will occur on the days 7, 8 and 9 of december, as an online event, from 8h to 11h. “Efficacy can not be compared over vaccines. Each one has a study, a certain way to define its efficacy and that is not comparable. What can be comparable is the efficiency”, he said.

During his participation at the discussion tables, after the scientific discussions, the doctor and technical director of the State Hospital of Serrana, Gustavo Volpe, one of the researchers of the effectiveness study of the Project S, endorsed the speech of Dimas affirming that comparing the types of immunizing  is wrong since they have different gaps of confidence, which is a statistical question.

“We need to pay attention to the effectiveness at the population we are observing. Comparing it’s wrong. The vaccines are tested in different scenarios, at different pandemics levels. If you are vaccinating a population that has more crowding control, the efficacy levels get really increased”, said. This difference of scenarios explains why the efficacy of the same vaccine can change in a real life context, during the effectiveness studies, explains the doctor.

“The study held by Butantan that identified the efficacy of 50,8% was in a population too exposed to the possibility of contagious [professionals of health], therefore it was the lowest. But reality imposes itself. What we witnessed on a large scale was a sensible reduction of cases, reduction in deaths and hospitalizations, and today we are in a situation more still, it is because of the vaccines, mostly because of CoronaVac. What we observe in Brazil today is what we observed in Serrana months ago”, explained Gustavo.

Dimas recalled that it is exactly because of these changes in the scenario that the effectiveness studies tend to bring different results of the clinical trials. “When you see the mass vaccination, you see the results. So, there is no difference in the point of view of the results between CoronaVac and any other vaccines”, completed the president of Butantan.