Now that more than half of adults in the United States have been inoculated with at least one dose of a Covid-19 vaccine and a third are fully vaccinated, paradoxically, academic rumors are multiplying that exclude it can soon to arrive to what last year, when we were very far from the goal, seemed a distant horizon, but absolutely to be conquered: herd immunity.
We don’t care like we used to
A paradox that derives from the fact that at that time we did not even know when (and if) a vaccine would be available, but we were convinced that sooner or later it would give us the magic “threshold” of herd immunity (that quota of vaccinated people who kills the circulation of viruses, effectively protecting even those who do not get vaccinated). Now that the vaccine exists, precisely in the countries that are further ahead with the vaccination campaign, the “state of the art” can be seen with data in hand and the distance between what one can hope for in a more or less distant future is measured. is what you can get now. In short: herd immunity is still “a mirage”, but it doesn’t “matter” as it did before, in some countries we have a good share of generalized immunity which allows you to return to normal and protect the weakest and, while the vaccination campaign continues, “coexistence” with the virus becomes possible.
The threshold of immunity to be reached rises
Why is herd immunity an elusive goal? First the calculation on the percentage of people serving as threshold: at the beginning it was estimated at around 60-70% of the population. The predominant variant currently in circulation in the United States, Italy and a large part of Europe, the English variant (B.1.1.7), is about 60% more transmissible. As a result, experts now calculate that the immunity has risen to at least 80%. If even more contagious variants develop, or if it turns out that vaccinated people will still be able to transmit the virus, the calculation will have to be revised again on the upside. The variants in circulation are one of the unknowns that have the greatest influence on the calculation of the threshold. The other is how long the protection will last offered by the vaccine or infection.
The Covid-19 situation in Italy and in the world
Unvaccinated layers of the population
The vaccination campaign, then, precisely in the countries where it is at its most advanced stage, is slowing down: it is not just a matter of resistance or opposition to vaccines (which in any case exists, in more or less large percentages and which may change over time), but also of difficulty in reaching certain sections of the population and poor persuasion towards the less at risk groups (the youngest), so much so that in some nations have offered incentives for children. Let us not forget, then, that herd immunity will never be complete without vaccination of the children: if it is not possible to vaccinate them, it will take many more adults to reach the quota for herd immunity, just think that in the United States almost 24% of people are under the age of 18. Pharmaceutical companies are preparing clinical trials, but time and ad hoc information campaigns will be needed.
Children need to be immunized
“In any case, it will be impossible to achieve community immunity at least in the future without vaccinating minors, given that even a number of adults will not want or will not be able to get vaccinated”, comments the immunologist Antonella Viola, professor of Pathology at the University of Padua. “Much will also depend on how the virus mutates and how our immune system responds: if acquired partial immunity is sufficient to block the most serious effects of the virus, it is likely that Covid-19 will begin to look like a flu, due to which we count some victims every year, but which generally does not cause serious illness. If, on the other hand, the virus begins to evade the immune response induced by vaccines, also due to the emergence of variants, it will take longer to make it behave like a seasonal flu ».
National imbalances
Last consideration: the vaccine will not go everywhere. There are huge differences in the efficiency of vaccine distribution between countries (even within them), but in a globalized world with a widespread pandemic it will be difficult (as it was in the beginning) stop the virus on national borders. In some areas of the same state there may be pockets of vaccine resistance where disease outbreaks develop. If coverage is 95 percent on average in a country, but 70 percent in some small town, the virus could make its way around that city. The case of India, where the pandemic is out of control, brings us back to the theme of the globalized world and why we have reached a pandemic: the exchanges are continuous and the virus knows no borders.
Infections decrease anyway
The finding that perhaps herd immunity will never be achieved leaves no room for disillusionment, as many scientists and rulers are coming to the conclusion that the virus will most likely become one. manageable threat. The New York Times In a recent article on herd immunity he recalls that Dr. Anthony Fauci, the Biden administration’s top adviser on Covid-19, acknowledged this shift in perspective: “People thought we would never be able to reduce infections until we would not have reached this “mystical” level of herd immunity, whatever its number. Here because we have stopped using herd immunity in the classical sense. Let’s forget it for a second. If we vaccinate enough people, infections will decrease, ”said Fauci.
The goal is to make the new coronavirus more like its cousins that cause the common cold. To return to normal life and protect the weakest, the threshold is not so high: data from countries ahead of vaccinations indicate that contagions collapse, as well as hospitalizations and deaths. The virus is circulating for now, but with the tests and other containment measures that we know well we can keep it under control.
May 4, 2021 (change May 4, 2021 | 08:57)
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