Covid: research is progressing, we now know why patients vaccinated with two doses have developed serious forms of the disease

Since the start of the Covid-19 pandemic, many researchers have been interested in a crucial question: how to explain that some patients infected with SARS-CoV-2 show no symptoms while others develop pneumonia that can go as far as at death? in a new study, Inserm looked at the rare severe forms observed in vaccinees, another major subject in the pandemic.

While all scientific studies have shown that vaccination against Covid-19 was effective in preventing severe forms of the disease, the fact remains that in fact, not all people reacted in the same way. Because some vaccinated people infected with SARS-CoV-2 have developed severe forms of the disease, requiring hospitalization.

What are Type 1 Interferons

Type 1 interferons (IFN 1) are a group of 17 proteins usually produced rapidly by body cells in response to viral infection and whose main effect is to inhibit virus replication in infected cells. There are several types, divided into several families: alphas, beta, omega, kappa and epsilon.

In some patients with severe forms of Covid-19, autoantibodies directed against type 1 interferons have been found. Neutralizing the action of IFN 1, these auto-antibodies therefore prevent the body from defending itself well against the virus.

The cases are very rare but they are the subject of very specific monitoring by Inserm (The National Institute of Health and Medical Research). The challenge is to understand why patients vaccinated with two doses were hospitalized following an infection with SARS CoV-2.

An essential subject in the understanding of the vaccination process on which researchers from Inserm, AP-HP and teacher-researchers from Paris Cité University within the Imagine Institute have carried out work which highlights a deficit immunological in some of these patients.

The research teams led by Pr Jean-Laurent Casanova and Dr Laurent Abel, co-directors of the human genetics of infectious diseases laboratory, have tried to better understand this phenomenon. In their study, they recruited 48 patients aged 20 to 80 who had a severe to critical form following an infection with the delta variant, despite a complete vaccination schedule with an mRNA vaccine.

In the end, the scientists demonstrate that 24% of the individuals followed in this study present auto-antibodies that neutralize the action of type 1 interferons., proteins that constitute the first immunological barrier against viruses. These results are published in the journal Science Immunology.

It is therefore an immunological deficiency in some of these patients which would explain the appearance of serious forms even after two doses of vaccine according to the Inserm press release.

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