Introduction
Early in the COVID-19 pandemic, children and adolescents were thought to
be important transmitters of the disease but were also believed to be
only mildly affected.1 Later, evidence increased that
children are not major spreaders.2,3,4 However,
reports of a multiorgan immune syndrome in children and youths surfaced
from Italy, the UK and the US,5 occurring weeks to
months after the SARS-CoV-2 wave. Studies in clinical
settings6 and assessments of registry data from
different countries followed,7 and suggested the
association of the multiorgan immune syndrome and SARS-CoV-2 infections
in children and youths.
The syndrome was named pediatric multiorgan immune syndrome (PMIS),
pediatric inflammatory multisystem syndrome temporally associated with
SARS-CoV-2 (PIMS-TS) or multiorgan immune syndrome in children (MIS-C).
It features many characteristics of the Kawasaki disease but it also
showed some peculiar differences. PMIS ranges from 3 to 17 years while
Kawasaki disease usually presents before the age of 5 years. Cardiac
dysfunction and shock as well as gastrointestinal and neurologic
symptoms are more frequent in PMIS.8 Interestingly, an
association of Kawasaki disease with coronavirus infections has been
discussed even before the COVID-19 pandemic.9
Recent studies linked PMIS to the presence of antibodies to SARS-CoV-2
and some authors suggested that high levels of antibodies against
SARS-CoV-2 may in fact contribute to the occurrence of the
syndrome.10 However, these observations were based onpost hoc measurements of antibodies in children who had already
acquired PMIS and had been hospitalized for severe symptoms.
We speculated that if strong antibody responses occur in children after
SARS-CoV-2 infection, which could be causal for the onset of PMIS, they
should be present before PMIS manifests or while the disease is still
mild and thus, could be used to detect those children at risk to develop
severe PMIS. Thus, we to screen a large number of children in rather
severely affected areas of Bavaria (Southern Germany) for neutralizing
and overall antibody levels against SARS-CoV-2 in the first pandemic
wave. Children with significantly elevated antibody responses were
evaluated clinically for signs of PMIS using a three-stage work-up
protocol.