Received Feb 11, 2026
| Type | Name | Manufacturer | Dose | Lot | Route / Site |
|---|---|---|---|---|---|
| FLUX | INFLUENZA (SEASONAL) (NO BRAND NAME) | UNKNOWN MANUFACTURER | UNK | — | OT |
tachycardia; Unintentional intravenous administration of the seasonal influenza vaccine/inadvertently administered an otherwise routine polyvalent influenza vaccine intravenously; single episode of emesis; crying with a severe headache; fever; Background: Adverse effects stemming from intramuscular influenza vaccination administration are typically mild, self-limiting, and well documented. However, a dearth of literature exists related to intravenous (IV) administration, having only previously been described once. We report the case of a two-year-old who was inadvertently administered an IV dose of the seasonal influenza vaccination. Hypothesis: IV administration of the influenza vaccine may result in a more dramatic immune response that would improve with symptomatic care. Methods: This is a single patient chart review. A two-year-old with a past medical history of IgA deficiency, was inadvertently administered an otherwise routine polyvalent influenza vaccine intravenously. The patient did not have a history of egg allergy. Nine hours later, the patient presented to the local emergency department crying with a severe headache and reported fever with a single episode of emesis at home. Vitals: tachycardia at 156 bpm, afebrile, and normotensive. Physical exam did not reveal any respiratory difficulty or rash. Results: The poison center recommended symptomatic care. The patient was treated with 15 mg/kg of acetaminophen and 0.5 mg of ondansetron, discharged five hours later with improvement. Conclusion: To our knowledge, this appears to be the first documented incidence of unintentional IV administration of a seasonal influenza vaccine in a pediatric patient. There is a single prior case series from 1979. A trivalent influenza vaccine was administered after being misidentified as a heparin flush. A patient developed myalgias and a fever of 39.1.C within 18hours. Antibody titers later confirmed exposure. Beyond the IV penicillin the patient had already been receiving prior to this exposure, no additional therapeutic interventions were administered and no further symptoms developed. Injection of the influenza-specific antigens induces an inflammatory innate immune system-mediated response that subsequently primes the adaptive immune system. As IV administration of an influenza vaccine results in more rapid uptake of the viral antigen, it is plausible this route of administration may result in a more exaggerated immune response and subsequent symptomatology. Our patient had full symptom resolution and was discharged home without incident. Our case supports minimal toxicity with intravenous polyvalent influenza vaccine administration. Initial information received on 04-Feb-2026 via other health care professional regarding an unsolicited valid serious case issued from a literature conference abstract: This case involves a 2-years-old and unknown gender patient who experienced tachycardia, single episode of emesis, crying with a severe headache and fever while receiving vaccine Influenza vaccine (Latency: 9 hours). The patient's past medical treatment(s), vaccination(s) and family history were not provided. Patient with a past medical history of IgA deficiency, was inadvertently administered an otherwise routine polyvalent influenza vaccine intravenously (produced by unknown manufacturer lot number not reported via intravenous route in unknown administration site, other dosing details unknown) (Incorrect route of product administration). The patient did not have a history of egg allergy. On an unknown date, nine hours later, the patient presented to the local emergency department crying with a severe headache (headache) and reported fever(pyrexia) with a single episode of emesis (vomiting) at home. Vitals: tachycardia at 156 bpm, afebrile, and normotensive. Physical exam did not reveal any respiratory difficulty or rash. Results: The poison center recommended symptomatic care. The patient was treated with 15 mg/kg of acetaminophen and 0.5 mg of ondansetron, discharged five hours later with improvement (corrective treatment). Author stated that: Adverse effects stemming from intramuscular influenza vaccination administration are typically mild, self-limiting, and well documented. However, a dearth of literature exists related to intravenous (IV) administration, having only previously been described once. We report the case of a two-year-old who was inadvertently administered an IV dose of the seasonal influenza vaccination. Hypothesis: IV administration of the influenza vaccine may result in a more dramatic immune response that would improve with symptomatic care. Conclusion: To our knowledge, this appears to be the first documented incidence of unintentional IV administration of a seasonal influenza vaccine in a pediatric patient. There is a single prior case series from 1979. A trivalent influenza vaccine was administered after being misidentified as a heparin flush. A patient developed myalgias and a fever of 39.1.C within 18 hours. Antibody titers later confirmed exposure. Beyond the IV penicillin the patient had already been receiving prior to this exposure, no additional therapeutic interventions were administered and no further symptoms developed. Injection of the influenza-specific antigens induces an inflammatory innate immune system-mediated response that subsequently primes the adaptive immune system. As IV administration of an influenza vaccine results in more rapid uptake of the viral antigen, it is plausible this route of administration may result in a more exaggerated immune response and subsequent symptomatology. Our patient had full symptom resolution and was discharged home without incident. Our case supports minimal toxicity with intravenous polyvalent influenza vaccine administration. Information regarding batch number and expiration date corresponding to the one at time of event occurrence was requested. Seriousness Criteria: hospitalization for all the events Action taken: not applicable. Corrective: acetaminophen for fever and headache; ondansetron for the event emesis; and symptomatic care for rest events. Outcome: recovered/resolved for all the events Reporter Causality: Related This suspected adverse reaction report is submitted and classified as a medication error solely and exclusively to ensure the marketing authorization holder's compliance with the requirements set out in the Directive 2001/83/EC and Module VI of the Good Pharmacovigilance Practices. The classification as a medical error is in no way intended, nor should it be interpreted or construed as an allegation or claim made by the marketing authorization holder that any third party has contributed to or is to be held liable for the occurrence of this medication error.; Sender's Comments: Sanofi company comment on dated 10-FEB-2026: This case involves a 2-years-old and unknown gender patient who experienced tachycardia, single episode of emesis, crying with a severe headache and fever while receiving vaccine Influenza vaccine (Latency: 9 hours). Based on the limited information received the causal role of VACCINE cannot be excluded due to compatible temporal relationship of ADR to the VACCINE. Further information regarding concurrent condition during vaccination, previous vaccination, tolerance, laboratory investigations excluding alternative etiologies for the reported event are needed to fully assess this case. Based upon the reported information, the role of vaccine cannot be assessed completely.
IgA deficiency
Comments: The patient did not have a history of egg allergy
Test Name: heart rate; Test Result: 156 {DF}; Comments: tachycardia; Test Name: Physical exam; Result Unstructured Data: did not reveal any respiratory difficulty or rash; Test Name: Vitals; Result Unstructured Data: afebrile, and normotensive