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The coronavirus vaccine race this week has shown labs – and their lagging countries – “on the heels” in terms of announcements.
That of the American pharmaceutical company Pfizer – which is one of three tested in the country – confirmed that its formula is 90% effective. Just 48 hours later, the Russian government said that of Sputnik V – which Argentina will receive in December – reached 92%. What is the best vaccine?
As they explained to Bugle three of the most eminent Argentinian infectologists, that of Moscow and Yankee lack end results and are based on preliminary clinical trial data. They both recounted what happened to a specific group of people, at a specific time, after a specific single dose, when the presumed immunity to both vaccines would begin after the second injection.
So to date there is no better vaccine than another. Because there is still no vaccine against the coronavirus. There are methods to test its efficiency and effectiveness. That they are not either.
Since vaccines are vaccines, science has focused on whether a puncture could save the world and has gone from old preparations under a microscope to genetic decoding of the virus to isolate a protein – in the case of Covid-19, the point or point, which gives it its “crown” shape – to “upset” it at will and inoculate it to generate antibodies. Despite all these biotechnological advances, the Golden Rule in search of the perfect dose: test that it is effective (other than effective) and test that it has a real impact on the community regarding the virus.
How is the effectiveness of a vaccine tested? Edgardo Bottaro, infectologist in the infectology department of Santojanni hospital and member of the staff of Helios Salud, explains to Bugle from inside the lab, where he cares for sick people and volunteers to fight the disease by testing Janssen’s experimental vaccine.
the The ABCs of these injections, as mentioned above, did not change with the hepatitis or SARS-CoV-2 vaccine. “In double-blind, randomized clinical trials – the ones scientists prefer – neither the researchers nor the subjects recruited know what was given to them. This modality aims to avoid prejudices in including people in one or the other group, which would interfere with the correct result of the study ”, explains the doctor.
How are these clinical investigations? They consist in defining a population which have never suffered from the disease (with certain inclusion and exclusion criteria defined by the research group) and divide it at random, so that one part of this population receives a vaccine and the other receives a placebo which in most case, is only a saline solution.
From there, you work “blindly”. With eyes wide closed but the biological data of each volunteer carefully checked. At a precise moment, predetermined by the research protocol, an evaluation of the preliminary results is made to know not if the vaccine is effective or not (it will fail for that) but “if it is useful and ethical continue the investigation or whether it should be suspended. “
“The evaluation times, the number of subjects to be included, the number of expected events (the Covid disease) and the percentage of expected efficacy depend on complex calculations which take into account statistical and biological variables”, specifies Bottaro. There is no table or Excel for this. Each group defines it. And there is the point that differentiates the effectiveness according to Pfizer or according to Sputnik V for their vaccines.
“When you evaluate a vaccine versus a placebo, you are evaluating the disease incidence rate in each of the groups. If in one group there are 100 people with Covid disease and in the other there are only 5, you have an efficiency of 95%, for example. But we have to see what the clinical specification of these volunteers is: whether they are clinical cases of Covid (due to bilateral pneumonia, for example), confirmed cases (by PCR) or suspected cases (by close contact ). It can be very different in the Sputnik V and Pfizer protocols. Although, in general, vaccine studies use confirmed cases of Covid after injection, ”he says Bugle Omar Sued, President of the Argentine Society of Infectology (SADI).
Sputnik’s estimate is based on preliminary data from a phase III clinical trial involving 40,000 volunteers, 16,000 of whom have already received the two doses that make up the vaccine. It was “calculated on the basis of the 20 confirmed cases of Covid-19 distributed between the vaccinated individuals and those who received the placebo. The efficacy was demonstrated on the basis of a first interim analysis obtained 21 days after the first injection “, read in the statement, signed by the Gamaleya Center in Moscow. It remains to be seen what happens after the second dose.
“In the Pfizer ad, they mentioned that in 90% of cases, the volunteers were asymptomatic (43,000 participants having received both doses). It is different to talk about efficacy, that is to say that vaccine does not prevent infection from entering. when infected, they do not show symptoms, they don’t cause complications and they don’t die. This is good news, but we have to see how comparable it is to Sputnik V. Today we cannot find out because the two studies are not published with definitive results, “says Sued. The protocol Sputnik V testing has not yet been released.
A researcher working in the Russian laboratory for vaccination against the coronavirus Sputnik V.
For Bottaro, as “at the moment we have no objective data allowing us to know which of the vaccines currently in development against COVID-19 is better”, there is a return to the theory of vaccines.
Differentiate efficiency, which speaks of how much the incidence of disease is reduced among those who received the vaccine versus those who were not vaccinated in a clinical research study, efficacy, which is the ability of a previously approved vaccine to protect against disease to people vaccinated in the community. It is also possible to measure effectiveness by reducing the incidence of severe forms, hospitalizations or deaths (as Sued explains in the case of Pfizer).
“The main difference is that the conditions under which the vaccination is carried out in the clinical study are somewhat ‘ideal’, while the results obtained in the community are ‘real life’ results influenced by variables absent in the clinical study. The setting for a clinical research study is sort of ‘artificial’ because it doesn’t exactly reflect what’s going on in people’s day-to-day lives, ”he says.
Precisely the effectiveness (and not the effectiveness), for Bottaro, “will allow us to know the impact of the vaccine -another important concept-, that is to say reduce the incidence of illness due to vaccination compared to the incidence of this disease before vaccination. “
In other words: while effectiveness is the data that will allow the Ministry of Health and ANMAT to approve the vaccine for use in the community, the effectiveness and impact will be the results that we most interested.
“Efficacy and impact data will not be available at the time of vaccine approval. To obtain them, it will be necessary to monitor the effects of the vaccine on the population to define its effectiveness and carry out actions aimed at solving the emerging problems which threaten it, ”warns the specialist. For example: if a vaccine was very effective in phase III studies, but at the time of their massive application “there were unfavorable situations within the population” – due to mistrust of vaccines, geography unfavorable to ultra-cold transfer, economic problems, costs, poor access to information, difficulties in accessing vaccines – the efficacy will be lower than its efficacy and the impact will be less than expected . “
If effective, how long does it protect?
Just as Bottaro says that it is not known which of the two vaccines is better than the other, it is not known how long the immunity of the two lasts.
Is one of the aspects to consider regarding the effectiveness of a vaccine is that of durability of the “protection conferred”: Whether the immunity obtained immediately after the completion of the full vaccination scheme is maintained over time or weakens, and this weakening of immunity correlates with a greater propensity to get sick.
The conclusion is that the modality is the same for vaccines of the past and those which are currently being tested: having an effective and effective vaccine that has an impact on the population implies that it has succeeded in overcoming the strict filters that will prevent approval. vaccines that have shown side effects, relevant enough to make the cure worse than the disease. “We must remain calm,” closes the infectologist.
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