What we know about whether patients who have passed COVID-19 can become infected again

When it was made public that "Patient 1" from Turin had returned to positive for SARS-CoV-2 after three weeks of hospitalization and several negative tests. In fact, city doctors had already officially declared him recovered. The problem is that it is not the only isolated report (and the largest studies speak of up to 14%) that has made the phantom of reinfection fly over all the work that is being done around the coronavirus.

And it is that, although it may not seem like it, it is an essential subject. The big problem with this coronavirus is that it is new and, unlike other diseases, no one has immunity. In other words, the virus can move with extreme ease from one human being to another without encountering resistance and making thousands of people sick in a very short period of time (collapsing the health system). We are doing what we can to stop this epidemic, but are we condemned to live it over and over again? That is, is there immunity after infection?

The reinfection debate


As the Pan American Health Organization (PAHO) pointed out, "as it is a new virus, and from which we are still learning more every day, at the moment we cannot say with complete certainty that a person who has been infected with the virus cannot become infected again "; however, public health experts work with the idea that people cannot be reinfected (at least in the short term). There are several reasons to believe it.

First of all, what we knew about other coronaviruses. Coronaviruses are a family of RNA viruses that, as such, have high mutation rates. Usually, there are multiple variants of each virus within the same person. However, the experience with human coranaviruses is that an immunity was generated that could last between three months and 15 years. Even this is not enough to confirm it, it is a strong indication that SARS-CoV-2 could do the same.

Second, preliminary animal studies seem to point out that the virus does indeed generate immunity. Here several problems arise. The first is the lack of comprehensive and reliable studies on the phenomenon. The teams are working against the clock and although the evidence is accumulating little by little, it is not giving time to refine it and replicate it with all the guarantees. The second is that we have been studying the virus for a very short time.

It is not surprising that the body generates short-term immunity against various pathogens. However, it takes more than a few weeks of immunity for "herd immunity" to occur. And the truth is that, with current studies, we cannot know how long the coronavirus would apparently last. The absence of this data is, without a doubt, one of the great weaknesses of all contingency plans that use herd immunity as an asset against SARS-Cov-2.

And thirdly, what leads us to think that, in general, a person cannot be reinfected is that there is no clear evidence of reinfection, the cases we are talking about are rather "apparently cured" patients who return positive . It is true that, in the first moments of the pandemic, the researchers thought that they were reinfections, but, when analyzing the cases in more detail, everything seems to indicate that they are spikes in viral load and antibodies.

These rebounds, even if they are not indications of reinfection, are also very important because they are relevant to the need (or not) to keep patients in quarantine once they have overcome the disease. In fact, some reports talk that this post-disease isolation should be extended up to 14 days to avoid spikes in the viral load and, therefore, the risk of contagion to third parties. This, in fact, is already being applied in China.

Beyond these indications and partial evidence, the protocols on possible reinfections are in full update. As countries return to normal in Asia, fear that the epidemic will hit them again has made monitoring methods more extreme. Soon many of the doubts that still exist on this subject will be clarified.

Image | Health.mil

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