A pioneering study yields encouraging results on immunity to covid | Society

Almost half of the Valencian population has been infected by the SARS-CoV-2 coronavirus. More than 97% have antibodies against the virus because they have been infected or because they have been vaccinated or both. And at least 75% have memory T cells, lymphocytes also known among experts by the epithet of “killers” because they attack and destroy infected cells and protect the body against the most serious cases, stopping hospitalizations and deaths. deaths.

All the above data come from the recent seroprevalence study carried out in the Valencian Community from samples taken between two and three weeks ago from a thousand people of various age groups in a hundred health centers. The data, however, can largely be extrapolated to Spain, with possible variations of one or two points, and yields an encouraging result in terms of the current immunity of the general population with respect to the known variants of covid-19. , according to David Navarro, the scientific director of the Valencian Research Program on the Covid-19 Vaccine of the Presidency of the Generalitat, and the epidemiologist Salvador Peiró, responsible for the study.

“We have carried out an analysis, on the one hand, of the antibodies, and on the other, of the T lymphocytes, which is newer and provides us with valuable information to act later and have an idea more adjusted to the reality of the situation. . The novelty also lies in the fact that we look at the antibodies that neutralize the omicron variants and not just the ancestral strain, that of the Wuhan virus, as in other studies, in order to measure the level of antibodies that act directly preventing the virus from infecting the cells of our body”, explains Navarro, Professor of Microbiology at the University of Valencia.

T lymphocytes are a type of cell found in the blood and lymphatic tissue that destroy cells infected by viruses and control the body’s immune responses against them. We also colloquially call them killer because they destroy the infected cells, preventing the virus from multiplying in them and they fight against the infection”, adds Peiró.

The analysis of these lymphocytes is especially important because they reveal the level of protection against the most serious cases of the disease. 75% of the people analyzed in the field work have this cellular memory, although it is estimated that the real percentage is even higher, because not all of them may be detected at the time of the test. Until recently it was complex to measure these cells, but now there are several techniques, such as the one used in this study, which will soon be published in an international scientific journal.

Other communities, such as Madrid, have recently announced the preparation of similar seroprevalence studies, with special attention to T lymphocytes, after the first ones carried out in 2020 by the Carlos III Health Institute related to the previous strains. The Valencian experts point out that no relevant variations are detected in the samples collected in the three provinces, Alicante, Castellón and Valencia. They maintain that the global behavior in Spain could be very similar, except for some autonomies, with a very high incidence of the coronavirus.

The study finds that 48% of the population, in a weighted prevalence data, has been infected by the virus, which means almost double the official count of positives in the Valencian Community, which rises to about 1.3 million, 25% of the total, right now. The age group with the highest number of infections is between 17 and 26 years old, above 70%.

All the data, and in particular, obtaining information on cellular immunity, is very useful when making decisions about inoculating the fourth dose of the vaccine, for example, or about what can be expected in the coming months of the pandemic, according to Peiró. “The results are good, almost 100% of the population has antibodies, half have been infected, it is a good immunity; We do not expect a significant rise in severe cases and hospitalizations with the cellular immunity that we have, unless the strain changes and one with an enormous vaccine escape capacity is introduced. So now we would not recommend putting the fourth dose of the vaccine in the Valencian Community, to see if it can last until October, ”he adds.

The search for so-called herd immunity, as was intended at the start of the pandemic, has long since been forgotten, with the finding of reinfections even in vaccinated people. Experts estimate that cellular immunity could last for more than a year and point out that hybrid immunity, which is obtained after having passed the infection and been vaccinated, is the most powerful and lasting.

This seroprevalence study is the latest work of those carried out by the Valencian Research Program on the Covid-19 Vaccine that emerged in March 2021 at the initiative of the President of the Generalitat, Ximo Puig, in parallel with the vaccination campaign, explains Ana Berenguer, general director of Analysis and Public Policies. “After several waves, we contacted the Carlos III Health Institute to prepare this seroprevalence study and they have supported us in its preparation, interested in also extrapolating the results,” she says. The purpose of Provavac is to deepen the scientific understanding of the effectiveness, immunity and possible adverse effects associated with vaccines.

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