{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T02:16:49Z","timestamp":1788229009375,"version":"build-2803163510"},"reference-count":23,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T00:00:00Z","timestamp":1787875200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Children"],"abstract":"<jats:p>Background: COVID-19 vaccination has demonstrated a favorable safety profile in children; however, factors associated with the occurrence of adverse events (AEs) following immunization remain insufficiently characterized. This study aimed to identify the demographic and clinical factors associated with AEs following COVID-19 vaccination in children aged 5\u201311 years. Methods: We conducted an ambispective observational cohort study in Madrid, Spain, including children aged 5\u201311 years vaccinated with the 10 \u00b5g formulation of BNT162b2 (Comirnaty\u00ae, Pfizer-BioNTech). Data were obtained from vaccination registries, electronic health records, and structured telephone interviews with parents or legal guardians. Demographic characteristics, anthropometric variables, previous SARS-CoV-2 infection, medical history, and concomitant medication use were evaluated. Univariable analyses and multivariable logistic regression were performed to identify factors independently associated with the occurrence of suspected AEs. Results: A total of 2026 children were included. Suspected AEs were reported in 759 participants (37.5%). In univariable analyses, greater weight, height, pre-existing medical conditions, concomitant medication use, clinically vulnerable status, and previous SARS-CoV-2 infection were significantly associated with AEs. In the multivariable model, previous SARS-CoV-2 infection (OR 4.07, 95% CI 3.13\u20135.30), number of concomitant medications (OR 7.77, 95% CI 5.22\u201311.56), number of pre-existing medical conditions (OR 1.86, 95% CI 1.62\u20132.14), and height (OR 1.03, 95% CI 1.01\u20131.04) remained independently associated with AEs. Age, sex, body mass index, and clinically vulnerable status were not independently associated with AE occurrence. Conclusions: In this large real-world pediatric cohort, previous SARS-CoV-2 infection, comorbidity burden, and concomitant medication use were independently associated with adverse events following COVID-19 vaccination. These findings suggest that underlying clinical complexity may be a more important determinant of post-vaccination reactogenicity than demographic characteristics and support the value of individualized pre-vaccination assessment in pediatric populations.<\/jats:p>","DOI":"10.3390\/children13091160","type":"journal-article","created":{"date-parts":[[2026,8,28]],"date-time":"2026-08-28T18:33:52Z","timestamp":1787942032000},"page":"1160","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Risk Factors Associated with Adverse Events Following COVID-19 Vaccination in Children Aged 5\u201311 Years: A Real-World Observational Study"],"prefix":"10.3390","volume":"13","author":[{"given":"M\u00aa \u00c1ngeles","family":"Rivas Paterna","sequence":"first","affiliation":[{"name":"Unidad de Cuidados Intensivos Pedi\u00e1tricos, Hospital Cl\u00ednico San Carlos, Calle Mart\u00edn Lagos s\/n, 28040 Madrid, Spain"},{"name":"Unidad de Recuperaci\u00f3n Postanest\u00e9sica, Hospital Cl\u00ednico San Carlos, Calle Mart\u00edn Lagos s\/n, 28040 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1725-0383","authenticated-orcid":false,"given":"Carla","family":"P\u00e9rez Ingidua","sequence":"additional","affiliation":[{"name":"Departamento de Enfermer\u00eda, Facultad de Enfermer\u00eda, Fisioterapia y Podolog\u00eda, Universidad Complutense de Madrid, Avenida Complutense s\/n, 28040 Madrid, Spain"},{"name":"Servicio de Farmacolog\u00eda Cl\u00ednica, Hospital Cl\u00ednico San Carlos, Calle Mart\u00edn Lagos s\/n, 28040 Madrid, Spain"},{"name":"Instituto de Investigaci\u00f3n del Hospital Cl\u00ednico San Carlos (IdISSC), Calle Mart\u00edn Lagos s\/n, 28040 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5357-4583","authenticated-orcid":false,"given":"Ana B. Rivas","family":"Paterna","sequence":"additional","affiliation":[{"name":"Departamento de Enfermer\u00eda, Facultad de Enfermer\u00eda, Fisioterapia y Podolog\u00eda, Universidad Complutense de Madrid, Avenida Complutense s\/n, 28040 Madrid, Spain"},{"name":"Instituto de Investigaci\u00f3n del Hospital Cl\u00ednico San Carlos (IdISSC), Calle Mart\u00edn Lagos s\/n, 28040 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"given":"Bel\u00e9n","family":"Joyanes Abancens","sequence":"additional","affiliation":[{"name":"Unidad de Cuidados Intensivos Pedi\u00e1tricos, Hospital Cl\u00ednico San Carlos, Calle Mart\u00edn Lagos s\/n, 28040 Madrid, Spain"},{"name":"Unidad de Recuperaci\u00f3n Postanest\u00e9sica, Hospital Cl\u00ednico San Carlos, Calle Mart\u00edn Lagos s\/n, 28040 Madrid, Spain"},{"name":"Departamento de Pediatr\u00eda y Salud P\u00fablica, Facultad de Medicina, Universidad Complutense de Madrid, Avenida Complutense s\/n, 28040 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0333-6242","authenticated-orcid":false,"given":"Esther","family":"Aleo Luj\u00e1n","sequence":"additional","affiliation":[{"name":"Hospital Infantil Universitario Ni\u00f1o Jes\u00fas, Av. 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Hyg."}],"container-title":["Children"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2227-9067\/13\/9\/1160\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T01:23:47Z","timestamp":1788225827000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2227-9067\/13\/9\/1160"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,28]]},"references-count":23,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["children13091160"],"URL":"https:\/\/doi.org\/10.3390\/children13091160","relation":{},"ISSN":["2227-9067"],"issn-type":[{"value":"2227-9067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,28]]}}}