This surveillance system was established by Santé publique France in collaboration with representatives from six pediatric medical societies*, who formed a steering committee. Its objectives were initially to verify the validity of this alert, and subsequently to identify these atypical clinical presentations that appeared to correspond to a post-COVID-19 syndrome.

Starting on April 30, 2020, all hospital pediatricians were asked to report to Santé publique France every new case of PIMS potentially linked to COVID-19, as well as, retrospectively, any cases that had occurred since March 1, 2020. Public Health France quickly developed an application allowing practitioners to report these cases online using a dedicated questionnaire developed in collaboration with pediatricians on the steering committee. A classification of these cases into four categories was decided upon collectively with the pediatricians, taking into account both their clinical characteristics and their link to COVID-19. In fact, there was no international classification of PIMS cases at the time this surveillance system was established. The daily monitoring and analysis of reports entered into the database were the responsibility of Santé publique France, as were follow-up emails to reporters to clarify the COVID-19 status and the progression of cases. The case classification was reviewed and the database analyzed on a regular basis, and the results were discussed regularly and collaboratively with the pediatricians.

This study identified 108 cases with a possible, probable, or confirmed link to COVID-19 among the 156 reported cases, thereby confirming the link between the development of this syndrome and infection with SARS-CoV-2.

It should be noted that the epidemic curve for these cases follows, with a 4- to 5-week lag, the same trend as that of hospitalized cases in France, and the same observation can be made regarding their geographic distribution, thereby corroborating the hypothesis that PIMS is a post-infectious manifestation of COVID-19. The description of similar cases in other countries (England, Italy, the United States, etc.), with these same temporal and spatial characteristics, reinforces this conclusion.

The results of this study constitute the largest series of post-COVID-19 PIMS cases described to date, although it is important to note that this is a rare phenomenon.

Surveillance will continue as long as cases persist (see below for instructions on reporting these cases to Santé publique France). Furthermore, the descriptive analysis of these cases, as reported in the article, constitutes the first step in a broader research process. It will serve as the basis for more in-depth studies of these cases, requiring further investigation at the clinical, immunological, genetic, and virological levels. This research-oriented phase will be carried out by the pediatricians on the steering committee, who will follow up with the clinicians who reported the PIMS cases in order to continue these investigations based on the patients’ medical records and better document this syndrome.