Emilia vexler
11/14/2020 4:24 PM
Clarín.com
Society
Updated 11/14/2020 4:24 PM
The race for the coronavirus vaccine this week showed laboratories - and their countries behind - "hot on the heels" of the ads.
That of the American pharmaceutical company Pfizer - which is one of the three that are tested in the country - confirmed that its formula is 90% effective.
Just 48 hours later, the Russian government said that that of Sputnik V - which Argentina will receive in December - reached 92%.
What is the best vaccine?
As
three of the most prominent Argentine infectologists
explained to
Clarín
, the Moscow and the
Yankee ones
lack final results and are based on
preliminary data from clinical trials
.
They both told what happened to a specific group of people, at a specific time, after a single specific dose, when the presumed immunity from the two vaccines would begin after the second injection.
So, as of today,
there is no better vaccine than another
.
Because there is still no vaccine against the coronavirus.
What do exist are methods to test
its efficacy and effectiveness
.
That they are not synonymous.
Since vaccines are vaccines, science focused on the fact that a puncture could save the world and went from the old preparations under a microscope to the genetic decoding of the virus to isolate a protein - in the case of Covid-19, the
spike
or spike, which gives it its "crown" shape - to "twist" it at ease and inoculate it to generate antibodies.
Despite all these biotechnological advances, the
golden rule
in search of the perfect dose
remains
:
prove that it is effective (different from effective) and prove that it has a real impact on the community regarding the virus
.
How is the effectiveness of a vaccine tested?
Edgardo Bottaro, infectologist at the Santojanni Hospital Infectious Disease Service and a member of the Helios Salud staff, explains it to
Clarín
from inside the laboratory, where he deals with sick people and volunteers to stop the disease by testing Janssen's experimental vaccine.
The
ABCs of these injections, as stated above, did not change with the hepatitis or SARS-CoV-2 vaccine.
"In double-blind randomized clinical trials -the ones preferred by scientists-, neither the researchers nor the recruited subjects know what was administered to them. This modality has the objective of
avoiding bias in the inclusion of people to one group or another
, which which would interfere with the correct result of the study ", explains the doctor.
How are these clinical investigations?
They consist of defining a population that
has not previously suffered from the disease
(with certain inclusion and exclusion criteria defined by the research group) and dividing it randomly, so that a portion of that population receives a vaccine and the other receives a placebo that, in most cases, it is just saline.
From there, you work "blindly".
With eyes tightly closed but the biological data of each volunteer
carefully controlled
.
At a specific time, 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 be lacking) but "if it is
useful and ethical to
continue with the research or if it is must suspend ".
"The evaluation times, the number of subjects to be included, the number of events expected (the Covid disease) and the percentage of expected efficacy depend on complex calculations that take into account statistical and biological variables", clarifies Bottaro.
There is no table or Excel for that.
Each group defines it.
And there is the point that differentiates the efficacy according to Pfizer or according to Sputnik V for their vaccines.
"When you are evaluating a vaccine against placebo, what you evaluate is
the incidence rate of the disease
in each of the groups. If in one group there are 100 people who have Covid disease and in the other there are only 5, you have an efficacy of 95%, for example. But you have to see what the clinical specification of these volunteers is: if they are clinical cases of Covid (for bilateral pneumonia, for example), confirmed case (by PCR), or suspected case (by contact This may be very different in the protocols of Sputnik V and Pfizer. Although, in general, in vaccine studies, confirmed cases of Covid post injection are used, "says
Omar Sued, president of the Argentine Society of Infectology
, to
Clarín.
(SADI).
Sputnik's estimate is based on preliminary data from a Phase III clinical trial involving 40,000 volunteers, of whom 16,000 have already received the two doses that make up the vaccine.
It was "calculated based on the 20 confirmed cases of Covid-19 divided between vaccinated individuals and those who received the placebo. Efficacy was demonstrated based on a first interim analysis obtained 21 days after the first injection," it reads 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 the cases, the volunteers were asymptomatic (43,000 participants who received the two doses). That is different from talking about efficacy, that is, this vaccine does not prevent the infection from entering But
when they become infected they do not cause symptoms
, they do not cause complications and they do not die. That is good news but we have to see how comparable it is with Sputnik V. Today we cannot know because both studies are not published with final results ", Sued points.
The protocol for the Sputnik V tests has not yet been released.
A researcher working in the Russian Sputnik V coronavirus vaccine laboratory.
For Bottaro, as "at this moment we do not have any objective data that allows 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 the efficacy, which talks about
how much the incidence of a disease is reduced
among those who received the vaccine compared to those who were not vaccinated in the framework of a clinical research study, from the effectiveness, which is the capacity of an already approved vaccine to
protect
people who were vaccinated in the community
against the disease
.
It is also possible to measure effectiveness by reducing the incidence of severe forms, hospitalizations or deaths (as explained by Sued in the case of Pfizer).
"The main difference is that the conditions in which vaccination is carried out in the framework of the clinical study are in a certain way 'ideal', while the results obtained in the community are results of 'real life' influenced by variables absent in the clinical study. The framework of a clinical research study is in a certain way 'artificial', since it does not reflect exactly what happens in people's daily lives, "he says.
Precisely the effectiveness (and not the efficacy), for Bottaro, "will allow us to know the impact of the vaccine -another important concept-, that is,
the reduction of the incidence of a disease from vaccination
compared to the incidence of that disease before vaccination. "
In other words: although efficacy is the data that will allow the Ministry of Health and ANMAT to approve the vaccine for use in the community, effectiveness and impact will be the results that most interest us.
"
The effectiveness and impact data will not be available at the time of approval of the vaccine.
To obtain them, it will be necessary to monitor the effects of the vaccine in the population to define the effectiveness and carry out actions aimed at solving the emerging problems that attempt against it ", warns the specialist.
For example: if a vaccine was shown to be very effective in phase III studies, but at the time of its massive application "there were unfavorable situations within the population" - due to distrust of vaccines, unfavorable geography for transportation under ultra-cold, economic problems , costs, poor access to information, difficulties in accessing vaccines - the effectiveness will be less 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 both lasts.
Is that one of the aspects to consider about the effectiveness of a vaccine is the
durability of the "protection conferred":
if the immunity achieved immediately after the completion of the application of the full vaccination scheme is maintained over time or if weakens, and if this weakening of immunity is correlated with a greater propensity to get sick.
The conclusion is that the modality is the same for the vaccines of the past and those that are being tested now: having an efficient and effective vaccine that impacts the population implies that it has successfully overcome the strict filters that will prevent the approval of those vaccines that have shown adverse effects, relevant enough that the remedy is worse than the disease.
"We have to stay calm," closes the infectologist.
Look also
The AstraZeneca and Oxford vaccine will begin to be produced in Argentina on November 23
Secrets, details and challenges of the distribution of a coronavirus vaccine