After cases of multisystem inflammatory syndrome in children spiked during the pandemic for reasons experts are still working to understand, now data shows MIS-C cases are declining so much they have all but disappeared, ABC News reported July 13.
Throughout the pandemic's duration, the CDC documented 9,499 cases of MIS-C and 79 related deaths. However, this past winter weekly cases only hovered around 10, according to ABC. The increase of cases during the pandemic linked COVID-19 positivity to the onset of MIS-C in some children.
Some research on the condition, which is known to cause inflammation of organs like the heart, lung, kidneys and even brain, suggests that its cause could be genetic, making some children more prone to it than others. The condition is also notoriously underreported in children, a separate study found.
"We had a protocol and an algorithm that we followed at our hospital, like many other hospitals, and if there was concern that a patient had MIS-C, back in the early days from 2020 through 2021, we would get a phone call on our infectious disease service," Samuel Dominguez, MD, PhD, an associate professor of pediatrics at Children's Hospital Colorado told ABC News. "And we were receiving many phone calls a week evaluating children's MIS-C and treating children for MIS-C, and now, it's almost unheard of. I can't remember the last time we got a call with any concerns for of MIS-C. So, that's really good news."
While experts are unclear exactly what is now causing a steep decline in MIS-C cases, some suggest that COVID-19 immunity — from both infection and vaccinations — have increased protection and as a result, have stopped triggering the onset of the condition in pediatric patients.
Experts also believe newer variants causing less severe infections may also be a factor. Certain variants have also shown differences in leading to MIS-C cases. The condition surged during the widespread delta variant, but was not as prevalent with omicron, according to ABC.