“Immune debt” is an “unsubstantiated theory” for these scientists

JEAN AYISSI / AFP A child suffering from bronchiolitis is on a drip November 29, 2003 in the emergency room of the Trousseau hospital in Paris. A major hospital doctors’ union today called for “coordination” between hospitals and liberal medicine to limit the current massive influx of patients suffering from flu or bronchiolitis to hospital emergencies. (Photo by JEAN AYISSI/AFP)


The concept of “immune debt” has divided the scientific sphere since November, which marked the beginning of the bronchiolitis epidemic in France. (Illustrative photo: A child suffering from bronchiolitis is on a drip on November 29, 2003 in the emergency room of the Trousseau hospital in Paris.)

SCIENCE – “No solid scientific basis”. The theory of the a immune debt “Generated by the Covid-19 pandemic which would explain the surge in hospitalizations for bronchiolitis, the scientific field divides. While the epidemic linked to this virus, which can cause serious respiratory problems in newborns, remains a “ a very high standard” in metropolitan France according to the health authorities, epidemiologists explain al huffpost because this apparent correlation is too simplistic.

Following the explosion in the number of bronchiolitis cases that have been saturating children’s hospitals for weeks, some doctors are in fact calling for ” an immune debt linked to the confinements of 2020 and 2021 and to barrier gestures (masks, physical distancing, etc.). According to them, by dint of being protected from external pathogens, our organisms would have become more vulnerable to other viruses. Including RSV, which is the virus responsible for between 50% and 80% of cases of bronchiolitis in France.

A theory developed among others in a study published in August 2021 in the journal Infectious Diseases Now, and which was taken up by Health Minister Olivier Véran on November 13 on the set of BFMTV. “We wore the mask for 2 years, we had protection, there was a very weak epidemic and less immunization of the little ones”, it’s advanced.

Has our immune system “fallen asleep” due to childbirth?

But “This assumption is unfounded. “, according to Mircea Sofonea, professor of epidemiology and evolution of infectious diseases contacted by The Huffpost. The scientist judges that he rather “seductive” think of the humanitarian system as a muscle that should be trained, but that the mechanism is actually more complex.

“In the current state of knowledge on immunity to respiratory viruses and RSV, memory or non-specific immune cells, i.e. innate immunity, do not need on this time scale, that of a few months or years (…), to meet other pathogens to support themselves”, analyze. In other words, the period of confinement would have been too short to have reduced the effectiveness of our immune response.

Even if the ” immune debt » would exist, “No one has lived since April 2020 in a completely aseptic environment. Viruses, bacteria, pathogens surround us all the time on our skin, in our bowl of cereal, in our digestive tract. the researcher abounds.

Morgane Bosmel, virologist specializing in mucosal immunology, interviewed by The Huffpost, has a more nuanced opinion. The CNRS researcher at the Cochin Institute argues that ” there has been a very significant decrease in respiratory viruses with the confinements and that therefore ” now the immune system is a bit asleep He also adds that adults are also much more likely to be infected with RSV this year, thus passing the virus more easily to children.

If the researcher considers it logical that our immune system has weakened, however, she does not establish a direct correlation between the confinements since April 2020 and the virulent bronchiolitis epidemic.

Reporting of cases of bronchiolitis in the fall

But then, how to explain the number of current hospitalizations for bronchiolitis, which have reached record levels for more than 10 years? Partly for a postponement to this autumn of the infections that weren’t there at the beginning of 2022, replies Mircea Sofonea. “2021 saw two waves that allowed for transient herd immunity” it’s a “marginal circulation of RSV in early 2022”, develops the researcher. Immunity after bronchiolitis infection only lasts a few months, so cases would be delayed until this fall. Some ” the variations from year to year are difficult to explain”, complete.

Even the immunologist Sandrine Sarrazin cited in the columns of Parisian climatic and environmental factors, possible mutations of the virus, active circulation of other viruses, including SARS-CoV-2″ which could lead to an increase in cases of bronchiolitis.

Thus, the ” immune debt would be at best one of “theories” to explain the ongoing outbreak of the epidemic. On his Twitter account, the epidemiologist Antoine Flahaut does not hesitate to talk about it “intellectual laziness” doctors and pediatricians hurrying “shameless” in this analysis. “The concept of ‘immune debt’ is an illustration of our great ignorance in the field of immunology”, he claims.

If the concept divides, epidemiologists recall the importance of vaccination against bronchiolitis and barrier gestures. Mircea Sofonea therefore recommends limiting contact between adults and infants, but also wearing “systematically a mask” in their presence.

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