Multisystemic inflammatory syndrome in children (MIS-C) possibly related to COVID-19 Pfizer-BioNTech mRNA (BNT162b2) vaccine. A case report

INTRODUCTION: During the SARS-CoV-2 pandemic, COVID-19 vaccines were authorized and administered worldwide. The AEFI, (ESAVI in Spanish) epidemiological surveillance system in Mexico is in charge to identify, follow and report all the events suspected associated to vaccination. In Mexico COVID-19 vaccination started in the group of children aged 5 to 17 years in June 2022. The vaccination program for children only used the Pfizer-BioNTech mRNA (BNT162b2) vaccine. To date 7 million doses (46% of vaccinated people) have been administered to this group of age, which is approximately 5% of the COVID-19 cases in Mexico. CASE REPORT: Five-year-old male hospitalized because of abdominal pain and fever. One day before, he received second dose of Pfizer-BioNTech mRNA (BNT162b2) vaccine. During hospital stay appendicitis was ruled out and he presented: high inflammatory markers, and more than two signs of multisystem involvement (hepatitis, myocardial failure, and hematological disturbances). Patient met criteria of MIS-C according to the American College of Clinical Rheumatology Guidelines, CDC and WHO. There was a SARS-CoV2 PCR and antibodies against spike virus negatives, as occurs in 5% of cases. The case had a good resolution. CONCLUSION: COVID-19 vaccines administered in Mexico in are safe and efficient. Pfizer-BioNTech mRNA (BNT162b2) vaccine was administered to children. No reports of MIS-V were found in Mexico. Severe AEFI reporting general rates are 0.010 per 1000 doses applied. As of Aug 31, 2021, 21 335 331 individuals aged 12–20 years had received one or more doses of a COVID-19 vaccine, making the overall reporting rate for MIS-C after vaccination 1·0 case per million individuals receiving one or more doses in this age group. The reporting rate in only those without evidence of SARS-CoV-2 infection was 0·3 cases per million vaccinated individuals.