Is herd immunity to the new coronavirus a mirage?

Experts are divided on the subject, and a lot depends on what is meant by herd immunity: eradication of the disease, or limited circulation enough to allow a return to yesterday's life?

(photo: Noam Galai / Getty Images) Here, it's hard to even make plans, with the vaccination campaign continuing to change on a weekly basis. But elsewhere the percentages of immunized grow exponentially, and make the debate on herd immunity ever more current. Is this a possible goal? What percentage of the population needs to be vaccinated to stop the circulation of the virus? And if we succeed, what should we do to make it last over time? Questions that for now remain unanswered, with experts divided among the most optimistic, who consider it a plausible goal already in the coming months, and those who are skeptical about the real possibilities of stemming the pandemic before a few years.

The second group certainly includes WHO researchers, who in January dampened the enthusiasm for the start of vaccinations by declaring that it will not be possible to achieve something similar to herd immunity in the course of 2021, at least globally. This is mainly due to the inability to produce enough vaccines for the entire planet in a short time. Masks and spacing could therefore continue to keep us company for many more months. The experts consulted last month by Nature in an article that lists the five reasons why herd immunity for Covid-19 could turn out to be just a chimera are also of the same opinion.

The list includes the fact that vaccines most likely do not completely prevent the transmission of the virus, the fact that vaccinations do not proceed uniformly in all countries of the world, the risk posed by variants that could bypass vaccines, the unknown factor linked to the fact that we do not know how long the immunity provided by vaccines lasts, and the danger that vaccines produce a change in the habits of the population, and that the return of risky behaviors will give new impetus to the pandemic. br>
Other experts, as we said, are more optimistic. Also because it is not certain that the effects of herd immunity will only be seen when the circulation of the virus has completely disappeared. "We are not trying to eradicate Covid-19, we are simply trying to stop the uncontrolled transmission of the virus," Dale Fisher, an infectious disease expert at the National University of Singapore, told CNBC. "In this sense, herd immunity is a possible goal".

Even if the virus will remain with us, in short, with a high percentage of vaccinations among the categories at risk, we could already see hospitalizations and deaths. Enough to make Covid-19 a manageable disease without the need for draconian restrictive measures like those we have been used to in the last 12 months of the pandemic. The unknowns remain many, and it is likely that in the next few years we will see pandemic regurgitation in patches. But where vaccination coverage remains high, it is likely that Covid-19 will no longer represent an insurmountable problem. "Herd immunity is not a binary phenomenon - adds Fisher - many people think that it is either obtained or not, but there are obviously many gray areas in between".

An encouraging clue, in this sense , comes from Israel, where more than 50% of the population has already been fully immunized with the vaccine. Adding to the vaccinated patients who have already contracted (and defeated) Covid, the percentage of the immune population reaches 68%, and this means that the country is one step away from the 70% of immune people that is often cited wrong or right) as a threshold for the arrival of herd immunity. The effects of vaccinations should therefore already be visible, and indeed, the available data points precisely in this direction. In fact, since the nation lifted many of the restrictions introduced to limit the spread of the virus, cases continue to decline steadily. And not only among the vaccinated, but also in children under 16, a category excluded from the vaccination campaign. This - explained to the BBC Eyal Leshem, director of the Sheba Medical Center in Tel Aviv - is an unequivocal signal that herd immunity has begun to bear the hoped-for results. } catch (er) {} Read also

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