Covid-19: a second infection could be even worse

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The production of so-called “facilitating” antibodies during a first coronavirus infection could accentuate the severity of symptoms during a second infection, according to Italian researchers.

What if the symptoms of Covid-19 were more serious the second time? This is what Italian researchers from the Treviso public health department fear in the case of re-infection with SARS-CoV-2. They detail their thoughts in a document published in June by the journal BMJ Global Health.

In this text, they hypothesize that a first infection with SARS-CoV-2 or another coronavirus could predispose to more severe forms of Covid-19 in the event of a second infection. The mechanism in question is that of so-called “facilitating” antibodies, already observed for other coronaviruses such as MERS and SARS, for the dengue virus or for that of West Nile.

A stronger inflammatory reaction

Concretely, these facilitating antibodies, produced by the body during the first infection, would cause an abnormal immune response in the early stages of a second infection. This abnormal response could then delay the development of the infected person’s immune response against the virus. As a result, the body’s inflammatory response would be stronger and increase the risk of severe symptoms, sometimes even cytokine storms—this infamous runaway immune system response seen in patients with severe form of Covid-19.

“If confirmed, this hypothesis would have relevant implications for the treatment of Covid-19 and the development of an effective vaccine,” note the researchers in their publication. This risk is already known for vaccines, since some of them make recipients more susceptible to infection.

Two tracks to verify this hypothesis

This hypothesis must now be confirmed or refuted. The next objective for the Italian researchers is therefore first to verify whether “secondary infections due to other coronaviruses or repeated community re-infections of SARS-CoV-2 can explain the more serious forms of COVID-19 observed in certain countries compared to others”. Then, it will be necessary to check if, provided that the virus circulates and infects a significant proportion of the population, it causes “re-infections and more serious clinical characteristics” detail the researchers.

How will they verify this hypothesis? Researchers propose two strategies. The first, observational, consists in registering the persons screened by a serological test and who present anti SARS-CoV-2 antibodies in a special registry and in following them in time to detect the appearance of a possible serious form stimulated by facilitating antibodies.

The second, experimental, is based on an infection with SARS-CoV-2 of animal models in the laboratory, then on a re-exposure of these models to the virus to observe if a severe form of Covid-19 occurs.

While waiting to learn more, caution and respect of distancing measures remain in order, even for people who have already tested positive for Covid-19.