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Nirsevimab Side Effects

The most commonly reported side effects of nirsevimab include respiratory syncytial virus bronchiolitis, incorrect dose administered, and respiratory syncytial virus infection, based on 1,370 FDA adverse event reports from 2023 to 2025. 20.1% of reports found the drug to be ineffective.

#1 Reported: Respiratory Syncytial Virus BronchiolitisAll side effects ↓Top Co-Medication: ThiotepaDrug interactions ↓72% of Reports Are InfantDemographics ↓

Nirsevimab side effects

Percentages show how often each reaction appears relative to total reports for nirsevimab.

1
Drug Ineffective20.1%276
2
Respiratory Syncytial Virus Bronchiolitis18.5%254
3
Incorrect Dose Administered14.9%204
4
Respiratory Syncytial Virus Infection9.9%136
5
Bronchiolitis8.6%118
6
Pyrexia6.2%85
7
Cough5.6%77
8
Extra Dose Administered4.2%57
9
Respiratory Syncytial Virus Test Positive3.4%46
10
Product Storage Error2.8%38
11
Rash2.6%36
12
Oxygen Therapy2.4%33
13
Wheezing2.2%30
14
Apnoea2.1%29
15
Product Administered To Patient Of Inappropriate Age2.1%29

These are voluntary reports and do not establish that nirsevimab caused these reactions.

Report severity

61.8%Serious846 reports
38.0%Hospitalizations520 reports
2.8%Fatal38 reports

Seriousness is determined by the reporter, not by OpenClaim.

Nirsevimab drug interactions

Other drugs that appear in adverse event reports alongside nirsevimab. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Thiotepa0.2%3
2
Cyclophosphamide0.2%3
3
Levothyroxine-sodium0.1%2
4
Cholecalciferol0.1%2
5
Elagolix0.1%2
6
Palivizumab0.1%2
7
Busulfan0.1%2
8
Fludarabine-phosphate0.1%2
9
Omeprazole<0.1%1
10
Chlorotrianisene<0.1%1
11
Upadacitinib<0.1%1
12
Norethindrone<0.1%1
13
Ofatumumab<0.1%1
14
Oseltamivir-phosphate<0.1%1
15
Budesonide<0.1%1

Taken alongside

1
Cholecalciferol1.5%20
2
Ergocalciferol1.1%15
3
Famotidine0.5%7
4
Amlodipine0.4%6
5
Chlorotrianisene0.4%6
6
Vitamin-k0.4%5
7
Ondansetron0.4%5
8
Furosemide0.4%5
9
Albuterol0.3%4
10
Omeprazole0.3%4
11
Aspirin0.3%4
12
Levothyroxine-sodium0.3%4
13
Hydrocortisone0.3%4
14
Methylprednisolone0.3%4
15
Ampicillin0.3%4

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports nirsevimab side effects

33.9% of nirsevimab adverse event reports involve female patients and 43.1% involve male patients. The largest age group is infant at 72%. These figures reflect who reports side effects, not underlying risk.

Sex

Female33.9%
Male43.1%
Unknown23.1%

Age group

< 294.0%
2–112.0%
12–170.2%
18–642.3%
65+1.6%

What is nirsevimab used for

Conditions and purposes for which patients were taking nirsevimab when the adverse event was reported.

Antiviral ProphylaxisAsthmaAtrial Septal DefectBronchitisChronic Obstructive Pulmonary DiseaseDrug TherapyHeart Disease CongenitalHigh Risk InfantImmune Disorder ProphylaxisImmunisationInfantInfection ProphylaxisJaundice NeonatalMaternal Exposure During PregnancyMeningitis

Showing 15 of 31 indications

Nirsevimab brand names and reporting trend

Nirsevimab is sold under the brand name Beyfortus.

Brand names

Beyfortus306

Quarterly reports (2023–2025)

202320242025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking nirsevimab with another medication?

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