COVID-19 | Herd immunity is unlikely in BR, scientists point out


In the COVID-19 pandemic, much has been discussed about herd immunity against the new coronavirus (SARS-CoV-2). The idea is that, from a certain percentage of people infected by the virus, even those who have not yet had the disease would have less chance of becoming infected. With more than five million cases in the country, a group of researchers points out that this situation is not yet a reality for Brazilian states.

In a technical note, researchers from different national institutes and universities note that herd immunity is a distant possibility from Brazilians, through analysis of data on the epidemic in the country. Among the group are members of the Federal University of São João del-Rei (UFSJ), Federal University of São Paulo (Unifesp) and University of Brasília (UNB).

The country is still far from this immunity against COVID-19, because the rate considered to be minimal to achieve this type of immunization, according to the group of researchers, is 60% of those infected with coronavirus in the local population. On the other hand, it is worth noting that there are other studies that point to much lower contamination rates.

According to a survey by Brazilian researchers, the country is far from achieving herd immunity against COVID-19 (Image: Reproduction / Kjpargeter / Freepik)

COVID-19 cases in the states

From the survey carried out by the group, today, the states that have the highest estimates of the percentage of those infected with the coronavirus, including asymptomatic cases, are: Roraima (27%); Rio de Janeiro (23%); and Distrito Federal (20%). Averages considered to be lower than those required for herd immunity.

With more than one million cases of COVID-19, the state of São Paulo has an estimated rate of 15%. Now, the states of Santa Catarina and Paraná have the lowest estimates (7%), followed by Minas Gerais and Rio Grande do Sul (8%); and Mato Grosso do Sul (9%). “Our estimates point to the fact that in all units of the federation we are still a long way from what would be herd immunity”, defend the researchers in the technical note.

Research on coronavirus infections

“To perform the calculations, we used a model that consists of separating the entire population into six categories: proportion of susceptible individuals, that is, not immunized and not yet infected; proportion of exposed individuals, who are infected, but not yet contagious; proportion of symptomatic individuals, who are infected, contagious and with symptoms; proportion of infected and unreported individuals, usually mild and asymptomatic infected; proportion of hospitalized individuals; in addition to the proportion of individuals recovered from Covid-19 and immunized “, explains Fulvio Alexandre Scorza, professor at the Department of Neurology and Neurosurgery at Unifesp Paulista School of Medicine and one of the researchers involved in the technical note.

For Scorza, “the data show that in all units of the federation there is still an enormous distance from what would be herd immunity. Believing this carries an important risk, as it would entail many costs of lives in hospital care, not just short-term care. , but possibly for years, given the countless consequences of COVID-19, in addition to a greater fall in economic activity, caused by a situation of dismay resulting from an epidemic beyond control “.

More deaths by COVID-19

Another issue raised by the group of experts is that the numbers of deaths are probably higher than those recorded. To be more precise, the survey indicates that the actual number of deaths from COVID-19 must be at least 30% higher than current values.

“The factors that explain this difference are already known. In addition to the delay in notification of death by COVID-19 due to the delay in test results, there is a delay in testing after death, resulting in a false negative, and also the failure to perform the test. test, not counting the death being registered as due to Severe Acute Respiratory Syndrome (SARS) due to unknown cause “, details Scorza.

“It is essential that [as autoridades] base their decisions on the best available scientific evidence, so that they weigh alternatives and discuss the consequences of different courses of action. In this sense, they should seek, as an example, the conduct of extensive public campaigns to inform the population about essential care, the implementation of a comprehensive testing policy, in addition to conducting the process of flexibility, including the opening of schools, very carefully before the real one. pandemic control, at risk of serious consequences for its population “, concludes the researcher.

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