“You can get infected twice with Covid, but it doesn’t mean getting sick again”


(edited by Federica Mancinelli)

Last Monday a press release from the University of Hong Kong released the news that a 33-year-old man “had a second case of infection, diagnosed 4 and a half months after the first episode” of Covid-19. The study will be published in the journal Clinical Infectious Diseases and the World Health Organization has not released any confirmations or conclusions. While waiting for complete scientific data and information, we asked Professor Roberto Cauda, ​​Professor of Infectious Diseases at the Catholic University for an opinion.

Professor, since Monday the question everyone is asking is: can we get infected again with the coronavirus responsible for Covid-19? And how long, then, does immunity last? The Hong Kong case is currently the only one documented. Is reinfection possible with other coronaviruses?

In theory, given also this recent, at the moment, single reporting is possible reinfection with Sars-CoV-2, also taking into account that scientific articles have appeared in the literature that demonstrate a progressive decrease in the concentration of neutralizing antibodies Sars-Cov-2 especially in people who have suffered from a mild disease compared to those who have had more severe forms. However, I believe, based on the rarity of the reports, that this re-infection is very infrequent for Sars-Cov-2, while we know that it is not so rare for the other coronaviruses, since, causing very modest clinical forms, the immunity is short-lived.

The news we are all waiting for is that of a vaccine against Covid-19: at this point, if other cases of re-infection were confirmed, the doubt arises about the duration of protection and the possibility of achieving the hoped-for herd immunity

At the moment there are no data that assure about the duration of protection and what is the percentage of subjects protected to achieve herd immunity. We do not know what the protective antibody titer is and we do not know if other immune protection mechanisms, such as cellular immunity, also come into play. While taking into account this, I repeat single, case of re-infection reported in Hong Kong, I do not believe that this affects the validity of a future Covid-19 vaccine. In fact, it should be noted that the case documents re-infection but with the absence of disease, which is not a negligible detail. It is as if the re-infected subject maintains a sort of “protection” that does not prevent the infection, but does not give rise to the disease. There are already examples of vaccines that do this.

In the event of a “double infection”, even a person previously ill and then cured should therefore be vaccinated and, in any case, continue to apply the recommended prevention measures as all: social distancing, hygiene of hands and environments, use of masks.

As regards vaccination, as no type of vaccine is available at the moment, no opinion can be expressed as to whether or not it is necessary. In the case of re-infection, if the presence of the virus in the swab is demonstrated, it is prudent to implement all the prevention measures in order to prevent contagion.

On the eve of the reopening of schools and universities and the return to work, to the office and to common places, millions of people have increased attention and apprehension: in light of everything, what are the indications and measures to observe and apply for the next months?

While waiting for a vaccine protection that will not likely be available immediately, it is important that individuals, with a great sense of responsibility, scrupulously observe the prevention measures, that is: use of the mask, safety distancing, washing hands, avoiding gatherings. It will also be important, after a discussion with your doctor, to implement the anti-flu vaccination which, while not protecting against Covid-19, reduces the risk of a respiratory disease that could be confused with the latter, creating differential diagnosis problems and at the same time lead to a “traffic jam” of health facilities.


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