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The delta variant, much more contagious, makes it difficult to reach this goal even with 85% vaccinated
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Experts call to continue vaccinating because the drug does slow down the circulation of the virus and makes it possible to control the disease
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At this point in the covid-19 pandemic, talking about group or herd immunity (that is, the moment when the population becomes immune to a disease by having a certain number of people vaccinated) is misleading. It will not be enough to have 70% of the population vaccinated, as was said at the beginning, nor 85%, as was said later. The delta variant of the coronavirus, much more contagious and with a higher viral load than the previous ones, has marked a before and after in this disease: it is capable of spreading, although at much lower levels, also in vaccinated people. There are already several experts who, although they urge to continue clicking the largest number of people, ask do not set group immunity thresholds.
“With this variant we are more likely to not achieve group immunity, which is not a drama and does not change the fighting strategy. We must continue trying to vaccinate the largest number of people because, although we will not achieve global protection, it does allow us to functional control of the pandemic “, explains the epidemiologist and Head of Preventive Medicine at Hospital Clínic (Barcelona), Antoni Trilla. The message instilled is this: even when the highest vaccination rates are reached, the restrictions, although some may be softened, they will still be there.
The Rt of viruses
When a population achieves group immunity in a given disease, the reproduction index (the well-known Rt) is located in a stable and sustained way below 1, as explained by Trilla. That means the disease stops spreading. And a vaccine is enough for this. “It happened with the measles [mucho más contagioso que el coronavirus], for instance. Measles, a virus that has not changed for years and the vaccine protects you, from a young age, by 95%. Thus we manage to eliminate it and there are only small outbreaks in some places “, he says.
“Thanks to the vaccine, and if a variant does not appear, we will reach an endemic situation like the flu,” says epidemiologist Antoni Trilla
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But the same is not the case with the coronavirus, a changing virus and before which vaccines, very effective in preventing serious illness and death, do not prevent infection, however. And there is another factor, in addition: “The population moves and Catalonia is not impervious to it. In addition, they will appear variants that will be transmitted more and more easily and quickly “, adds this epidemiologist. That is why he insists on seek the maximum number of immunized, because the vaccine does hinder the circulation of the virus, which will allow gradually withdraw prevention measures. “So we will get there, if no dangerous variant appears, to a endemic situation: the virus will live among us and infect some people from time to time, as happens with the flu. “Covid-19, he says, will cease to be” the disease “to be “one more disease”.
Catalonia has set itself the goal of putting two million vaccines this September and thus reach 80% of immunized Catalans at the end of the month. Both in Catalonia and in all of Spain there are already 70% of people with the double guideline and, if the rhythm returns to what it was before the August break, it is foreseeable that in October are already vaccinated 90% of the Spanish.
Immunity decreases
According to the immunologist and researcher at the CSIC Matilde Cañelles, from the moment it has been shown that the vaccinated person can transmit the virus and that immunity decreases over time, “It is quite difficult to talk about what percentage of the population must be vaccinated to achieve group immunity.” “It is getting out of hand,” acknowledges Cañelles, who nonetheless sees “logical” for countries to set goals for themselves. “It was very logical to set the goal of having 70% of the population vaccinated in summer. In this regard, I am relatively optimistic: in this fifth wave, despite this variant, hospitalizations and deaths have fallen dramatically, the main objective to be achieved “, Cañelles account. For this reason, like Trilla, it calls for continuing vaccinations. But not only that: “It is time to start putting a third dose for those over 65 because our elders may be losing protection, “he claims.
“I am optimistic. In this fifth wave, despite this variant, hospitalizations and deaths have dropped a lot,” says the CSIC immunologist Matilde Cañelles
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This CSIC immunologist estimates that, in the coming months, Spain will keep the virus “controlled” thanks to the vaccine, although it will not disappear. He predicts that at least those over 65 will have to be vaccinated periodically. But he is optimistic and believes that “probably by the middle of next year” there will be no “waves” to begin to have “epidemic outbreaks”. “Unless a variant that invalidates immunity “, he clarifies. And, although he believes this fall will be better than the previous one, it will not be all as fast as initially thought.” They said that with 70% vaccinated [objetivo alcanzado ya en España] the problem would be over, and no “.
Objective: continue vaccinating
The epidemiologist and member of the Spanish Society of Epidemiology (SEE) Joan Caylà points out that what is happening in countries like Great Britain or Israel, that go back to living high rates of infections because they raised restrictions Hastily, it shows that having many people vaccinated does not guarantee transmission of the virus. “Thanks to vaccines, there have been no cases of measles for almost 10 years, only small outbreaks from an imported case. With covid-19, a behavior similar to that of measles can be expected. But there are years to go. A sixth wave is foreseeable, but less than the fifth. AND little by little there will be epidemic outbreaks “, explains Caylà, who considers “a priority” to have at least 90% of the population vaccinated.
For other experts, the concept “herd immunity” is still “very valid” because it indicates the speed at which the virus moves
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For the researcher of the Group of Computational Biology and Complex Systems (Biocomsc) of the Polytechnic University of Catalonia (UPC) Daniel López-Codina, the concept of group immunity, however, “remains very valid “ because it is an indicator of how the pandemic is evolving. “As herd immunity increases, so too it decreases the velocity to which the pandemic is transmitted, therefore the strategy should be to increase herd immunity. If we get to very tall models, we can raise some measurements. But now it’s time, at least, to keep the measurements as now “, López-Codina thinks.
Although it is impossible to make predictions about the pandemic, one possible scenario is that covid-19, like the flu, becomes seasonal. But, for that, you have to continue vaccinating because, with very high immunization percentages, “Controlling the pandemic will be progressively easier”, López-Codina insists.
Give air to the sanitary system
Reinforce this idea Ildefonso Hernández, spokesperson for the Spanish Society of Public Health (Sespas). “The perspective [de la pandemia] It has changed because, as we have increased knowledge, we have seen that the vaccine, although it has effects, does not prevent transmission. That makes virus reproduction parameters do not go to zero, especially for the delta variant “, explains Hernández.
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The vaccine is also important to download to the health system, which for more than a year has been overturned with the covid-19
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According to him, “It is highly unlikely that we will soon achieve herd immunity” as originally thought. But, like his colleagues, he insists: “We must continue vaccinating.” “There is an undoubted objective that is still there: that the health services regain their capacities “, This epidemiologist stands out, calling for the strengthening of public health services in Spain, which have always been underfunded. It also warns that “most of humanity remains unvaccinated”, which further favors the transmission of the virus and increases the risk of new variants.
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