Type, effectiveness, storage methods, doses and much more. To evaluate a vaccine we have several parameters available. But how to understand which is the best in a given context? These are the questions that researchers and leaders must face when they are called to select the serums on which to focus to put an end to a pandemic that has already caused more than 2.5 million deaths worldwide. A decision that must take into account the data and information we have so far, limited stocks and, at the same time, the need to act quickly.
Having many and different Covid vaccines in development, the World Health Organization reminds us, increases the chances of one or more successful ones. As of December 2020, there were over 200 candidates in development. Of these, at least 52 in human trials and many others in phase 1 or 2 of research. Three at the moment those authorized by the EMA, l’European Medicines Agency: Pfizer, Moderna, AstraZeneca.
But to date, based on the available data, as Nature writes, they are difficult to compare. And it could take months before they can be classified.
“We are facing the largest vaccination operation in the history of humanity. Times must be fast and in compliance with certain rules. Every day we learn something new: the recommended age for a vaccine, the number and spacing of doses; the reduced efficacy in the presence of variants; the combination of vaccines “, he said Roberto Cauda, full professor of Infectious Diseases at the Catholic University of the Sacred Heart in Rome.
Development and vaccines, times and phases: the special
“The control bodies give the green light only to vaccines that are safe and capable of allowing the control of the disease, to protect against its most serious forms. I refer to those approved by the EMA but also to those for which data have been published in journals international as for Sputnik, “he adds.
Coronavirus, vaccinations around the world: the special
Effectiveness and protection
In a context in which we must act quickly and stocks are limited, he writes Nature, any effort to classify vaccines must take into account not only their claimed efficacy, but also the supplies, costs, logistics of implementation, duration of protection, and the ability to repel emerging viral variants. Even so, it’s hard to take your eyes off the clinical trial results that suggest an efficacy gap.
“Greater effectiveness can have a better impact. But remember that, for example, if it is equal to 70% it is equivalent to that of vaccines that we have been using for a long time such as anti-flu vaccines.”
But the crucial point, adds the expert, is another: “We have to ask ourselves whether a vaccine prevents infection and disease or just disease. At this moment, in which we have the results of phase 3, there is no answer. In this phase of vaccine development, conducted in a very correct but also fast way, no swabs were made but we went to see how many fell ill with Covid. “The prevention of infection and therefore we do not yet know if the vaccinated can block the transmission.
There is a difference between efficacy and protection. They can coincide, but it must be verified.
“An efficacy of 95%, as for Pfizer, does not mean a protection of 95% of the vaccinated. It means that it reduces the number of new infections in the vaccinated population by 95% compared to the unvaccinated one”, explains the teacher. To have an answer it is necessary to wait for the results of the fourth phase of the vaccines, which begins when they become available.
Covid, when will vaccines bring us back to normal?
by Valeria Pini
Vaccines cannot be compared on the basis of effectiveness alone. The choices cannot be separated from the context. “In Great Britain, for example, AstraZeneca was chosen in the presence of the English variant by postponing the second dose. A winning bet. With Pzifer it would not have been possible” says Cauda.
The trials were conducted with different demographic samples. For AstraZeneca, for example, the developers have collected little data on efficacy in people over the age of 65. Hence the changes in age group indications, although the European Medicines Agency recommends it to all adults. Which is also happening to us in these hours.
Just as the period in which the experimentation took place in various countries is different. Each trial reflects the situation at a given time. “The efficacy data were made in the absence or with a very limited circulation of the variants. Again, phase four will give a definitive word,” explains Cauda.
Surveillance studies are needed
Each measure of effectiveness is accompanied by a degree of uncertainty, and trials may be based on different definitions of important criteria. Relevant aspect with the spread of viral variants.
Opinion
Covid: what if two vaccines are better than one? The English study
by Roberto Cauda
Researchers are studying vaccine doses and combinations. They don’t know how long immunity will last or how well the various vaccines will reduce the spread of the coronavirus. Surveillance studies are needed to monitor how they function in different situations.
Vaccine cards
.