[ad_1]
Imagine this scenario: a couple share everything in the same house, use the same bathroom, sit at the table, eat face to face, are snuggled up watching Netflix, and sleep together every night. But one is positive for COVID-19 and the other never gets the disease. How did this happen?
The answer is not yet definitive, but there are “clues”, the result of the efforts of the scientific community, which has dedicated itself to understanding the phenomenon, explains Carlos Almeida Nunes, specialist in Internal Medicine at the Lusíadas Hospital.
“One of them has to do with the possibility of the existence of crossed immunity,” he begins by pointing out. “People who have had more contact in the past with another coronavirus may have gained some immunity to SARS-CoV-2 – but not all,” explains the doctor.
I like? “We know that SARS-CoV-2 is a virus that belongs to the coronavirus family, a family of viruses that has been with us for a long time.” What happens is that this strain -which has turned the world inside out- is a kind of “mafia member of the family”, a member “who has degenerated.”
Even so, it may have similarities with some of the family members and, therefore, people who have had a cold or the common cold in the past, having been affected by certain types of coronavirus, may have developed an immune response.
That is why it is called cross immunity, not direct. “It was not this agent [o SARS-CoV-2] that caused immunity, but a relative. It did not determine so much the protection of antibodies, but the appearance of lymphocytes, which are our immune memory cells. [responsáveis pela resposta imune e pela defesa do corpo]”, Explain.” And these lymphocytes are marked in the future and probably forever, constituting a form of immunity. They are activated when the virus comes in contact with someone. “
“This is a possible explanation,” says the doctor. Several recent studies have pointed in this direction. “There are immunology studies that suggest that there is a natural immunity to SARS-CoV-2 in many people, which is the result of the immunity that already exists for the four coronaviruses that cause common colds and flu, it is cross immunity,” he said. quoted by “Diário de Notícias”, Portuguese researcher José Lourenço, from the University of Oxford, UK, who has been investigating group immunity.
Research carried out by Boston University, in the United States, and published in October, goes in a similar direction: it says that colds caused by other coronaviruses can be a protective factor against serious SARS-CoV-2 infections.
More clues: the tuberculosis vaccine
But there is another hypothesis that may explain why some people do not contract the virus, despite having close contact with positive cases. This clue may also explain why, in some people, the severity of the infection is substantially less.
“It is related to the individuals who made BCG – tuberculosis prevention vaccine. It is a very stimulating immunization vaccine. In our country, we vaccinate many people. There may be a link between immunity to COVID-19 in those who were vaccinated in the past, ”says Almeida Nunes.
It was part of the National Vaccination Plan for 50 years, having only been withdrawn in 2017. The great advantage of this vaccine is that it does not act only against the specific tuberculosis pathogen, increasing the immune response in relation to others – at least, in which have been vaccinated in the last 15 years.
Several studies have linked the lower severity and prevalence of COVID-19 in people who have received this vaccine. One of them was carried out by Israeli scientists, from the Ben-Gurion de Naveg and Hebrew universities in Jerusalem: published in July in the magazine “Vaccines”, The research led to the analysis of data from 55 countries, including Portugal, which suggests the existence of a relationship between the BCG vaccine and lower rates of COVID-19 infection and mortality from the new coronavirus, per million inhabitants. .
Several clinical trials have been conducted to see if, in fact, there is this relationship between the tuberculosis vaccine and the lower incidence and severity of COVID-19. One of them is Dutch and was published in August in Cells Report Medicine: it concludes not only that the vaccine “is not associated with an increased incidence of symptoms during the COVID-19 outbreak in the Netherlands,” but it also says that BCG “It may be associated with a decrease in the incidence of the disease during the Covid-19 pandemic and a lower incidence of extreme fatigue.”
According to the BBC, at the beginning of October, the University of Exeter, in the United Kingdom, began clinical trials that included 1,000 people, in order to see if, in fact, the peaty vaccine has this protective effect against COVID. -19.
The hypothesis that the BCG vaccine would be successful in the fight against COVID-19 emerged in the first months since COVID-19 was declared a pandemic. Tedros Adhanom Ghebreyesus, director general of the WHO, is the co-author of a scientific article published in the Lancet in April, in which he recognized that clinical trials had already shown that the immunological effects caused by the BCG vaccine “are capable of protecting against infections. respiratory “. “.
The article says that “BCG vaccine has been shown to reduce the severity of infections by other viruses” with structures similar to that of COVID-19 in controlled studies, such as the yellow fever virus and encephalomyocarditis. “Therefore, the BCG vaccine can reduce the presence of the virus after exposure to SARS-COV-2, resulting in less severe COVID-19 and faster recovery. “
However, it specifies that this vaccine should be used against COVID-19 only in controlled studies. There are four main reasons to take into account: the shortage of the vaccine, which means that its indiscriminate distribution for the fight against the new coronavirus could endanger the health of children who live in risk areas and who need this protection; after, the lack of knowledge of its real effectiveness with respect to SARS-CoV-2, taking into account the “weak evidence” of the studies carried out to date, based on population and not individual data; the false sense of security that can cause; and, finally, the need for careful monitoring to avoid the remote possibility that BCG could have the opposite effect and worsen the disease in infected patients.
[ad_2]
