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Specialists explain that this 'seronegativization' does not mean that patients have lost immunity and warn that the virus has mutations that could become complicated in a second wave with the flu.
With covid19 there are few certainties. The first known case is from the end of November in China and that, in terms of research to find out how the pathogen behaves and evolves, is a very short time. Scientists who are trying to find a vaccine know them, and also epidemiologists who are “learning as they go.”
The third wave of the seroprevalence study carried out in Spain has confirmed what was already predicted: only 4,8% of the Aragonese population has developed antibodies against covid-19, a little below the national average (5,2. 14%). The most surprising thing is that there have been XNUMX% of people who had antibodies and have stopped having them, which "accentuates the existing uncertainty about the protection generated after infection with this virus," the experts explain.
Is it something common? Does the same happen with other diseases? Antonio Rezusta, head of the Microbiology and Parasitology service at the Miguel Servet hospital, explains that there are people who are not capable of producing antibodies and who have been able to pass the covid. "There are two formulas to study the defense of organisms: one is the humoral route, which is the one with which we check the antibodies in serological tests, and the other is the cellular one, which is measured with T lymphocytes and not only with the immunoglobulins. This second aspect is still lacking in studies, so it cannot be guaranteed that people who have lost antibodies have also lost immunity to the virus. It would be necessary, therefore, to verify both mechanisms and that makes finding a vaccine against covid more complicated, more laborious and the studies can take longer. “The coronavirus is, however, one of the pathogens that has aroused the most studies, analysis, expectations and attention in professionals around the world. A lot of data has been deciphered, even more than about HIV, in record time,” explains Rezusta.
What is certain so far is that the virus mutates, so when a vaccine is given it is to be expected that it will have to be given several times throughout a lifetime with subsequent booster doses to stimulate the immune system. In this sense, it would be more similar to that of the flu, which varies every year (in 2009 it even had to be tested twice due to its mutations) than to that of pennyroyal or rubella, for example, which is valid for life although be administered in several doses. “But it is also risky to affirm that or say what effectiveness and protection time the hypothetical vaccine would have because the case mix is very varied,” explains the microbiologist.
There are many factors depending on both the virus (whether it arrives in attenuated waves or not) and the defenses and immune capacity of each patient. Thus, we must remember that diseases practically eradicated in many countries, such as measles or tetanus, still cause havoc in many others.
"The "loss" of antibodies is more common in young people who have not had symptoms"
But can someone who has already overcome it get infected with coronavirus again? Experts explain that yes, although it is assumed that in that case your body would respond sooner and better - even having lost the antibodies - because lymphocytes 'have memory'. The Minister of Health, Sira Repollés, explained a few days ago in Parliament that the PCR tests are now complemented by the so-called Elisa tests, which allow us to verify whether the infection is recent or the patient has developed antibodies for a longer time.
In fact, since last May 4, the Miguel Servet has this new serological technique, which uses electrochemiluminescence to detect if a patient has been exposed to the virus, with which some 4.000 results have already been obtained.
In the latest seroprevalence study, it points out that the "loss" of antibodies is more common in young people who have not had any symptoms and is not as common in those patients who suffered a sudden loss of smell or taste. Scientists have a clue there to continue their studies, which the director of the National Epidemiology Center, Marina Pollán, claims should be done through specific analyzes according to the sociodemographic characteristics of the population. For example, the elderly in nursing homes, so hard hit by the pandemic, would deserve specific attention, according to Pollán. In fact, the drugs that are now being tested in the fight against covid, see remdesivir or some plasma transfusions of those who have already overcome it, serve to stimulate the immunity of a group of specific patients with previous pathologies that are also very specific. , but they can be inane when treating other types of patients.
The studies carried out so far at the national level indicate that the number of people who did not have antibodies in the first wave and who have developed them in recent months after having contact with the virus has been falling (from 0,9 to 0,7%). and that would reflect “the low appearance of new infections after confinement.” Given the doubts regarding the degrees and duration of protection, we cannot but repeat the calls for caution and to maintain all types of precautions and security measures, whether or not the virus has been contracted.
