False hopes are often far worse than fear, as these years of pandemic have demonstrated. The illusions of security or lesser risk (“ah, this disease only catches in a country with a cold climate”; “ah, it’s just a cold”) were falling to the ground, one by one. Only one breath has remained so far: the much lower risk of a serious outbreak of Covid-19 in children. A Brazilian survey has taken some important steps to understand why this is – and to show that little ones cannot remain outside the global vaccination effort.
Here is the first crucial message of the work, confirming what other studies have already shown: there is no reason to believe that the probability of catching and transmitting the Sars-CoV-2 virus is lower in this age group.
“Children get infected and have high viral titers [grosso modo, o número de cópias do vírus circulando no organismo], probably contributing to the transmission, even when they do not have symptoms”, says immunologist Cristina Bonorino, a researcher at the Federal University of Health Sciences of Porto Alegre and co-author of the new study.
Bonorino, along with colleagues from other institutions in Brazil and the USA, has just published the results in the specialized journal Nature Communications. The team analyzed the reactions of the body’s defense system of 24 children treated at two hospitals in the state capital.
This group was compared to two others, consisting of 34 and 33 adults who had mild and severe versions of the disease, respectively. All people included in the study had undergone a PCR test, which detects the presence of the genetic material of the coronavirus in the body.
The comparison showed, to begin with, the abundant presence of virus genes in the bodies of pediatric patients. In general, paradoxically, the strongest reactions of the body’s defense system appear in adults with severe disease. But children’s bodies also tend to react strongly to the presence of Sars-CoV-2. The point is that this counterattack seems to be done differently from what is seen in adults.
One of the explanations for this may be the so-called innate immune system — defenses that, as the name suggests, come “from the factory” in the human body, without depending on previous contact with the virus. Children appear to carry a larger population of so-called dendritic cells, including a subpopulation of them that is crucial for antiviral defense.
Furthermore, the antibodies that infected children produce more often serve to block molecules in the virus’s structure, not the infamous protein S, which it uses to invade human cells.
Interestingly, the vaccines available today target only protein S. Perhaps it is a case of thinking about vaccines that stimulate the reaction to other molecules of the virus as well. In any case, “our article shows the importance of vaccinating children, because they transmit the disease”, says Bonorino.
“And those who have had Covid respond robustly to the virus. So the vaccine will provide the protection they need — one protection must add to the other.”
It is worth remembering that there is no successful vaccination strategy when you think only at the individual level. By definition, the shield brought by vaccines is collective. The more people included under that umbrella in Brazil and in the world, the more reasons there will be to have hope.
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