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The João Lobo Antunes Institute of Molecular Medicine (iMM) will conduct the largest national serological survey for Covid-19 and the most representative. 12,000 volunteers are needed and the tests, which determine if the person has been in contact with the virus and developed antibodies, are free..
The project will be carried out, which is financed with two million euros by the Francisco Francisco dos Santos Society and the Jerónimo Martins Group between September 8 and October 7, in 102 counties across the country. The results will be known from the end of next month.
“The purpose of the study is determine the proportion of the Portuguese population that developed antibodies against the SARS-CoV-2 virus, which makes it possible to estimate the prevalence of infection, by conducting free serological tests (…) ”, reads a statement sent to the newsrooms, indicating that there are 314 positions available at the Centro de Medicina Laboratorio Germano de Sousa for sample collection.
The study sample will be based on the “proportional stratification of the Portuguese population by age group – under 18 years, between 18 and 54 years or more – and the population density in the regions – low, medium and high”. Experts from Pordata and the Faculty of Medicine of the University of Lisbon contributed to the definition and characterization of this sample, the document also reads.
Of the 12 thousand participants, 2,200 minors under 18 years old (18%), 5,500 between 18 and 54 years old (46%) and 4,300 aged 55 and over (36%) will be required. To participate, just sign up on this website, and there is also a helpline available, through number 808 100 062, for more information about the project.
After completing this project, iMM will do a study of tracing to a subgroup of volunteers, for a year, in order to monitor your immune response over time.
Serological tests are different from tests that allow you to see if a person is infected or not. In this case, the blood test looks for antibodies that remain there after the presence of the virus.
When a virus or bacteria enters someone’s body, it reaches a cell and begins to multiply, triggering a response from the immune system, the way the body goes into combat mode to protect itself. In practice, the soldiers in this fight are antibodies – or immunoglobulins – that are being produced to face the threat.
“From the moment a person comes into contact with the virus, it settles in our cells and can only multiply inside. And it is only from a certain amount of virus in the cells that we detect it and only from certain symptoms the immune system becomes alert ”, explained to the Observer in April, in relation to another article, Germano de Sousa, specialist in Clinical Pathology and founder of one of the largest Portuguese groups of clinical analysis laboratories.
What are serological tests and what are they for?
This reaction, which can be detected in the laboratory, produces two types of antibodies: immunoglobulin M (IgM) and immunoglobulin G (IgG). The first is detected in the acute phase of the disease, which, in the case of Covid-19, is usually around the seventh day after the first symptoms. The second occurs later, between days 14 and 21. It is the latter that can translate future immunity, since it is already produced according to the invading virus or bacteria, being the moment in which “the organism begins to win the battle ”Says Germano de Sousa.
Basically, doing a serological test is to detect the presence of these antibodies in the body of a person, which can serve as protection against new “attacks”. For that, a simple, only qualitative test, which only involves a finger prick, will be enough to collect a drop of blood. But that alone says very little, it only confirms that there are antibodies in the body. A more complex test with a blood sample is needed to determine the amount of these antibodies.
From there, you need to take into account other elements of the equation. Having antibodies alone is not enough to guarantee immunity. And there is still no certainty about how long these antibodies remain in the human body, that is, how long the eventual immunity lasts (something that the study of tracing will also try to understand).
In July, the serological survey carried out by the National Institute of Health Dr. Ricardo Jorge – of much smaller dimensions than the one that the IMM wants to carry out – revealed less encouraging results. Revealed at the end of that month, the findings showed that only 2.9% of the population residing in Portugal had developed antibodies against the new coronavirus, that is, around 290 thousand people, not enough to create group immunity (which can vary) . between 40 and 70%) and less than in other European countries.
At that time, the study coordinator, Ana Paula Rodrigues, explained that Portugal was expected to have a low seroprevalence – “proportion of people with antibodies against the new coronavirus” – since the country did not have “an intense epidemic.”
Only 2.9% of the population of Portugal have antibodies against the new coronavirus. Not enough for herd immunity
The INSA admitted, however, that immunity to SARS-CoV-2 could be “underestimated” in that study, since only antibodies were taken into account and not cellular immunity, which will also have “an important role in the response immune ”. In fact, studies on MERS-CoV and SARS-CoV-1 show that there is a more durable response at the level of T cells, also known as memory cells, than at the level of antibodies, which have a more “short-lived” response. Something that happens especially in asymptomatic cases.
