For SBIm president, ‘herd immunity’ is only available with stable, non-mutable viruses like Sars-Cov-2; the lack of a vaccine that prevents infections 100% is also an obstacle.
A “herd immunity” happens when a population is exposed to a certain virus and, from the contact with the pathogen, people acquire a natural immunity, indirectly protecting those who were not contaminated. A study carried out by the Butantan Institute in the municipality of mountain, made with the vaccine CoronaVac and which had the results released in May this year, pointed out that the pandemic could be controlled and community transmission interrupted with about 75% of the population vaccinated. For Renato Kfouri, president of the Brazilian Society of Immunizations (SBIm), this goal is “unattainable”. “O In my opinion, a completely mistaken concept that many had been defending was never achievable”, says the doctor. Infectologist Ingrid Cotta from BP – A Beneficência Portuguesa de São Paulo, in turn, believes that the term “herd immunity”, which has been popularly propagated, is inadequate and “politically problematic”. “Flock immunity is a term that is not appropriate if used for Covid-19. It can even be used for other diseases that have a lower mortality rate. However, when we think about Covid-19, it is unacceptable to expect everyone to be contaminated and for this percentage of people to die so that someone can then be protected”, he says.
Experts still argue that the many variables surrounding the pandemic make it difficult to calculate exactly what percentage of vaccines would be sufficient to prevent the spread of the disease. Renato Kfouri lists three points to justify the impossibility of collective immunity: the fact that Covid-19 is a zoonotic disease, the high mutation rate of the coronavirus and the lack of a vaccine to prevent infections 100%. “The first is that Covid-19 is a zoonotic disease, that is, it does not only affect humans. Coronaviruses affect bats, snakes, aquatic animals, camels. So it is not a virus exclusive to human beings”, he points out. Thus, even with vaccination in humans, the coronavirus continues to circulate in other species. “The second point is that the coronavirus mutates. Variants appear and manage to escape both the immunity induced by a natural infection and the eventual immunity of vaccines. The way Delta emerged, other variants will emerge and will continue to emerge. So the coronavirus is a virus that mutates and the concept of herd immunity is achieved with stable viruses, such as measles, rubella and other, let’s say, eradicable diseases”, explains the president of SBIm.
The doctor also reminds that currently available vaccines are not able to contain the infection or transmission of the coronavirus. “ They are very good for preventing severe, mild and moderate forms of the disease, and are reasonable in their ability to reduce transmission”, he says. “Put all this together: it is a zoonotic virus, which undergoes mutations, and we have vaccines that are not capable of eliminating transmission and do not guarantee long-term protection, that is, it will be necessary to carry out a revaccination. it’s a goal [a imunidade coletiva], seeing me, unreachable,” adds Kfouri. Ingrid points out, however, that, at the moment, the vaccination remains the best way to face the pandemic. “We always have to keep in mind that the vaccines we are using today are working very well to prevent serious illnesses, hospitalizations and deaths and are working well against the Delta variant“, reinforces the BP doctor, who adds that hygiene measures are still essential.
“We have to adapt to this pandemic dynamic. Of course it is no longer what we experienced in 2020, but it is also not non-existent within our society and we are facing a variant that seems to reduce protection. So, in addition to vaccination and the booster dose, it is extremely important to keep using masks, preferably N95 or surgical, social distance, hand hygiene and, whoever can, stay at home,” says Ingrid. With vaccination and protective measures, Kfouri believes that the coronavirus should become endemic, as well as the influenza virus. “It will adapt and it will be a virus like the flu or any other respiratory virus, indistinguishable from others, like the H1N1 virus that circulates throughout the year in the country. The virus becomes endemic, acquires seasonality, affects the most vulnerable groups, but it does not do this damage. It is the virus’s adaptation and circulation mechanism in society. This is what most experts understand the virus to behave in the post-pandemic period”, concludes the president of SBIm.