Study finds Omicron has fewer and milder cases of MIS-C in children than Delta

A new UB study, conducted at John R. Oishei Children’s Hospital, is the first to reveal that there were fewer cases of multisystem inflammatory syndrome in children (MIS-C) during the pandemic ommicron wave than the delta wave. One of the studies. MIS-C is a rare but serious complication that occurs in children who have previously had COVID-19, and he has a mortality rate of nearly 1%. Published in the journal Viruses online on January 7, study The cases that occurred during Omicron were also milder than during Delta.

During both waves, Black children were disproportionately affected by MIS-C and were more likely to be hospitalized with COVID-19, as shown by many other studies. attributed this to systemic and structural racial health inequities, and because the study was not directed to its contribution to racial health disparities, this observation goes beyond We note that limited analysis was possible.

This study shows how the MIS-C landscape will continue to change as new COVID-19 variants evolve. At the same time, the author says it’s hard to say what that means for the future.

“That’s a tough question,” says senior author Mark D. Hicar, an expert in pediatric infectious diseases at UBMD and associate professor of pediatrics at UB’s Jacobs School of Medicine. “We don’t know why early strains of the virus caused him more MIS-C and why omicron caused less, so it’s hard to say whether future strains will be worse or better. .

Similarly, it’s hard to predict what the current strain XBB.1.5 will do, he says. Because this variant is starting to thrive in national data, it takes weeks for cases of MIS-C to emerge.

“Several recently published studies suggest that cases of MIS-C are becoming more serious, but they are based on data from 2021, when the Omicron wave actually begins. It’s the one before,” Hicar said.

“Our study is one of the first to show that MIS-C became milder and more rare during the change to Omicron,” he says. It continues, and according to anecdotal reports from colleagues across the country, MIS-C is now very rare.”

However, he adds that it is important to remain vigilant, as new strains of the SARS-CoV2 virus could cause an increase in the incidence or severity of MIS-C.

This retrospective study included 271 patients admitted to Oi Children’s Hospital from August 2021 to February 2022, which included the majority of delta waves and ohmic waves (BA.1 ) were the strongest.

The main strength of the study was that a panel of three infectious disease experts decided whether the child was hospitalized for COVID-19 or for some other reason, and whether the child happened to test positive for the virus. In each case, a judgment was made as to whether or not To avoid possible false positives, the UB study relied only on cases proven to be positive by PCR testing.

The panel, led by Patrick O. Kenney, an infectious disease specialist at UB, said that many children reported to have been hospitalized with only an incidental diagnosis of SARS-CoV2 on a PCR test were actually Founded after discovering experiencing. Symptoms not often seen in previous waves. These included croup, originally reported by other groups, and increased rates of seizures, bleeding events, and intra-abdominal inflammation, including pancreatitis and hepatitis.

“Reports at the time confirmed an increase in pediatric Omicron hospitalizations, but those reports focused on global hospitalization data,” explains Hicar. “We would like to have a thorough chart review by three infectious disease specialists to determine if the hospitalization was due to COVID-19, or for some other reason, or if they just happened to have COVID-19. I thought.”

According to Hicar, this detailed approach helps clarify how MIS-C is changing over time, especially in light of the decline in severe cases during omicron. In this study, during the delta period, MIS-C accounted for up to 12% of his Oishei hospitalizations, whereas during the omicron period he accounted for only his 6% of hospitalizations. Based on their data, the researchers estimate that his risk of MIS-C with Omicron in western New York is 32% lower than he was during the Delta period.

In this study, in Buffalo, pediatric hospital admissions increased during the Omicron wave, which was similar nationally, but both COVID-19 and MIS-C cases were higher than before the pandemic. They noted that it was generally less severe than the wave of Additionally, hospital stays at Daisei Children’s Hospital were relatively short as a result of MIS-C or COVID-19 during this period.

The researchers found that COVID-19-positive children who did not have MIS-C during the ohmic wave showed a wide range of symptoms, especially among younger children, including seizures, croup and related conditions with high fever. reported that. In contrast, the child who developed her MIS-C during Omicron had a narrower spectrum of symptoms. They had constant fever and abdominal or upper respiratory symptoms. The authors state that no patient even met the incomplete criteria for Kawasaki disease. Early in the pandemic, MIS-C was thought to resemble Kawasaki disease.

The authors note that the majority of children admitted to Oishei Children’s Hospital during Omicron with either COVID-19 or MIS-C were not vaccinated. Vaccines were made available prior to the start of the study and were available from age 5 to 11 during the study. Of her 107 children hospitalized with acute COVID-19 during Omicron, 88 had documented vaccine status. Of these, 5 were fully vaccinated and 1 received a single dose. The rest had not been vaccinated.

Based on local county data that showed that 33% of children under the age of 18 had been vaccinated when the Omicron wave began, it rose to 42.1% by the end of the study period. Hospitalization for either COVID-19 or MIS-C in children.

“Our data show that the vaccine is highly protective in preventing hospitalization in children, even during the major transition of the virus from Delta to Omicron,” says Hicar. .

In addition to Kenney and Hicar, co-authors are Arthur J. Chang, Omaha Children’s Hospital and Medical Center, and Lorna Krabill, a fourth-year medical student at the Jacobs School.