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

JEAN AYISSI / AFP A child suffering from bronchiolitis is on a drip on November 29, 2003 in the emergency department of the Trousseau hospital in Paris. One of the main unions of hospital doctors today asked for “coordination” between hospitals and liberal medicine in order to limit the current massive influx to hospital emergencies of patients suffering from influenza or bronchiolitis. (Photo by JEAN AYISSI / AFP)


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

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

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

A theory developed among other things in a study published in August 2021 in the journal Infectious Diseases Now, and which was taken up by the Minister of Health 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”, he advanced.

Has our immune system “fallen asleep” because of the confinements?

But “This assumption is unfounded. “, according to Mircea Sofonea, lecturer in epidemiology and evolution of infectious diseases contacted by The HuffPost. The scientist judges that he rather “seductive” to 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 to years (…), to encounter other pathogens in order to maintain itself”, he analyzes. In other words, the period of confinement would be too short to have reduced the effectiveness of our immune response.

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

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 little asleep “. Moreover, she adds that adults are also much more likely to be infected with RSV this year, thus transmitting the virus more easily to infants.

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

Report of cases of bronchiolitis in the fall

But then, how to explain the number of current bronchiolitis hospitalizations, which have reached record levels for more than 10 years? Partly by a postponement of infections that did not take place at the start of 2022 to this fall, answers Mircea Sofonea. “The year 2021 has seen two waves which have allowed transient collective immunity” and an “marginal circulation of RSV in early 2022”, develops the researcher. Immunity after bronchiolitis infection only lasts a few months, so cases would be postponed until this fall. Some ” year-to-year variations are difficult to explain,” he completes.

The immunologist Sandrine Sarrazin also mentioned in the columns of the Parisian climatic and environmental factors, possible mutations of the virus, the active circulation of other viruses, even of SARS-CoV-2 ” which could lead to increased cases of bronchiolitis.

Thus, the ” immune debt would be at best one of the “theories” to explain the ongoing outbreak of the epidemic. On his Twitter account, epidemiologist Antoine Flahaut does not hesitate to talk about “intellectual laziness” doctors and pediatricians who rush ” without restraint ” in this analysis. “The concept of ‘immune debt’ is an illustration of our great ignorance in the field of immunology”, he asserts.

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

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