What the label lists and what reports show
Nirsevimab side effects
Nirsevimab's FDA label: “Most common adverse reactions were rash (0.9%) and injection site reactions (0.3%).” FAERS holds 1,721 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is respiratory syncytial virus bronchiolitis (297 reports).
- No generic listed
Check it at the source: the nirsevimab FDA label on DailyMed (effective July 13, 2026); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of BEYFORTUS?Serious allergic reactions have happened with BEYFORTUS. Get medical help right away if your child has any of the following signs or symptoms of a serious allergic reaction: swelling of the face, mouth, or tongue difficulty swallowing or breathing unresponsiveness bluish color of skin, lips or under fingernails muscle weakness severe rash, hives or itching The most common side effects of BEYFORTUS include rash, and pain, swelling or hardness at the site of your child's injection. These are not all of the possible side effects of BEYFORTUS. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Source: FDA drug label, Sanofi Vaccines US Inc., effective July 13, 2026 (SPL set 2f08fa60-f674-432d-801b-1f9514bd9b39), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions were rash (0.9%) and injection site reactions (0.3%).
From the label: adverse reactions, continuedMost common adverse reactions were rash (0.9%) and injection site reactions (0.3%). ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Sanofi at 1-855-239-3678 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. A total of 3,224 pediatric subjects received the recommended dose of BEYFORTUS in Phase 2 and Phase 3 clinical trials (Trials 03, 04, and 05) including 2,119 infants who were born at 35 weeks gestational age (GA) or older, and 1,105 infants who were born at less than 35 weeks GA. A total of 247 infants of any GA with chronic lung disease (CLD) of prematurity or hemodynamically significant congenital heart disease (CHD) in Trial 05 received the recommended dose of BEYFORTUS. Neonates and Infants Entering Their First RSV Season (Trial 03 and Trial 04) Trial 03 was a randomized, double-blind placebo-controlled trial conducted in preterm infants born at a GA of greater than or equal to 29 weeks to less than 35 weeks. Subjects were randomized 2:1 to receive BEYFORTUS (N=968) or placebo (N=479) by IM injection. …
Source: FDA drug label, Sanofi Vaccines US Inc., effective July 13, 2026 (SPL set 2f08fa60-f674-432d-801b-1f9514bd9b39), via openFDA; the full label on DailyMed
What do FAERS reports show?
1,721 reports list nirsevimab among the medicines taken, each a report of something that happened, not proof the medicine caused it; 41 are coded as a death and 726 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 1 is named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Nirsevimab: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions