Testing positive for an antibody does not ensure immunity to the virus

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Testing positive for an antibody does not ensure immunity to the virus





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The coronavirus has also appeared in semen, according to researchers from China.


Passing the infection caused by SARS-CoV-2 once does not guarantee that, in the future, the same person will not be able to contract the coronavirus responsible for covid-19 again. Immunity, therefore, is not always guaranteed. The first analyzes carried out in Spain on the matter indicate that, among patients who have suffered the disease in a mild or asymptomatic way, 44% of people who have tested positive for those known as ‘rapid tests’ have a level of antibodies low and with little ability to re-neutralize the virus. That is this 44% of patients would not have developed the necessary ‘defenses’ for avoid a possible second SARS-CoV-2 infection. In contrast, people who have passed the disease developing more severe symptoms have found up to 10 times more antibodies.

The immunity puzzle it remains, in part, unknown. The results of this preliminary analysis suggest that antibody detection is not enough to guarantee total protection against the virus. In fact, among the samples analyzed in this work, it has been observed that at least half of the diagnosed mild or asymptomatic patients had developed defenses (hence the positive of the test) but, against all prognosis, these antibodies were not entirely ‘useful’ in stopping the virus again. In other words, that there are cases where weapons built to fight infection have turned out to be few and bad. Hence, once again, experts ask to maintain all security measures to avoid a possible contagion since, apparently, it is not clear to what extent the substances that our body produces to fight against this pathogen are an infallible shield Or, on the contrary, their effectiveness may vary depending on the circumstances.

It also remains to be resolved why in some cases ‘quality antibodies’ are developed and in others not. “We will have to study the reason for these differences, but in the meantime these results indicate that testing positive does not guarantee immunity against the virus“warns Julià Blanco, researcher at IrsiCaixa and the Germans Trias i Pujol Research Institute, one of the researchers responsible for the recently presented study. These results are presented this Wednesday under the research consortium formed by the IrsiCaixa AIDS Research Institute , the Center for Research in Animal Health (CReSA) of the Institute of Research and Agri-Food Technologies (IRTA) and the Barcelona Supercomputing Center (BSC), with the support of the pharmaceutical company Grifols.

Immunity against the virus

Research has analyzed 111 patient plasma samples who had tested positively known colloquially as ‘rapid tests’, an alternative to diagnostic PCR tests (with which the virus genome is analyzed) focused, in this case, on looking for samples of antibodies against SARS-CoV-2 in blood. The study, carried out in the high-level Biosafety laboratories of CReSA with the team of Júlia Vergara-Alert and Joaquim Segalés, has analyzed presence and ‘quality’ of these ‘shields’ against the virus. And, in addition, it has delved into the unknown of how the human body reacts to this infection.

In severe cases, where a higher level of antibodies has also been detected, the researchers believe that “this is probably because your immune system has been exposed to a higher amount of virus and this has caused it to react in a way more powerful, “as Blanco explains. In these patients it is estimated that the immune response was generated about 10 days later of the appearance of symptoms.

In mild cases, where a lower presence of antibodies has also been detected, experts believe that there could be other factors that have contributed to neutralizing the virus. There are people who, for reasons still unknown, could count on innate immunity to this virus. Or with cellular immunity capable of ‘destroying’ these pathogens once they reach the cells. “All this must be investigated further, but although it is shown that the containment of the first infection was due to these factors, we do not know if they will be equally effective in the case of a second exposure to the virus,” says Bonaventura Clotet, director of IrsiCaixa .

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