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Beyfortus®▼(nirsevimab): effectiveness and public health impact in the real world

Author : Sanofi
Editorial team

▼ This medicinal product is subject to additional monitoring.

Beyfortus® is indicated for the prevention of Respiratory Syncytial Virus (RSV) lower respiratory tract disease in:1

  • Neonates and infants during their first RSV season;
  • Children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.

Beyfortus® should be used in accordance with official recommendations.1

Beyfortus® has an unparalleled body of real-world evidence against RSV disease, including hospitalizations2–60

> 50 real-world studies in over 400,000 Beyfortus®-immunized infants across the Northern and Southern Hemispheres*,2-60
world map

A meta-analysis of 27 studies assessed the effectiveness of Beyfortus® against RSV-related outcomes in the real world61

The 27 studies included after screening/eligibility, was conducted in Spain, France, US, Italy and Luxembourg. Beyfortus® was associated with high effectiveness against RSV-related outcomes61:

meta analysis

Length of hospital stay: No difference between Beyfortus®-immunized infants and non-immunized infants was observed (weighted mean difference [WMD]: 0.10; 95% CI: -0.63–0.65; p=0.97)

The NIRSE-GAL study: A real-world effectiveness and impact study from Galicia, Spain60

Galicia, a region in northwestern Spain, became one of the first places in the world to introduce nirsevimab as part of its regional immunization program for infants. The study was conducted between September 25, 2023, and ended March 31, 2024. It included over 13,300 infants.2,60

After Beyfortus® implementation, RSV LRTI hospitalization decreased substantially by 89,2% vs. five previous seasons for infants in the overall cohort (infants born before and during RSV season).60

In this real-world study, high coverage was achieved in the seasonal and catch-up groups. High effectiveness and public health impact were seen with Beyfortus. The findings from this study support clinical trial efficacy and safety data.1,60,62,63

Watch the video below to learn more about the findings of the study:

The data in the video are expressed as relative risk reduction, while the corresponding absolute risk reduction is not reported in the manuscript.

▼Beyfortus had a favorable safety profile in clinical trials.1,62-65

Safety has been studied in a broad population, including healthy premature infants and children at higher risk of RSV infections of the lower respiratory tract. The type and frequency of adverse reactions with Beyfortus were comparable to placebo in the Phase 2b and Phase 3 studies.1,62-65

Rash

Rash

within 14 days of dosing

Pyrexia

Pyrexia

within 7 days of dosing

injection-site-reactions

Injection site reactions

within 7 days of dosing

Hypersensitivity reactions have been spontaneously reported after marketing authorisation; The frequency is unknown.1

In the study in infants at higher risk of severe RSV, the safety profile of Beyfortus was comparable to that of the comparator medicinal product palivizumab and consistent with the safety profile of nirsevimab in full-term and preterm infants at GA ≥ 29 weeks.1,62,65

* In Andorra, Australia, Chile, France, Italy, Luxembourg, Portugal, Spain, and the United States as of August 05, 2025.

** Results are reported as OR and WMD with 95% CIs. Statistical heterogeneity across studies was assessed using the I² and 𝜏𝜏² metrics; I2 values of 0–40% indicate low heterogeneity, 41–75% indicate moderate heterogeneity, and values greater than 75% indicate high heterogeneity.60 Tau2 (𝜏𝜏2 ) is the variance of the effect size parameters across the population of studies and reflects the variance of the true effect sizes.

† I2 = 0.0%; 𝜏𝜏2 = 0.000.

‡ I2 = 65.3%; 𝜏𝜏2 = 0.186.

§ I2 = 58.6%; 𝜏𝜏2 = 0.235. 60

¶ IQR: 89.1–91.4%.

▼This medicinal product is subject to additional monitoring. This will allow quick identification of new safety information. Healthcare professionals are asked to report any suspected adverse reactions.

Beyfortus® (nirsevimab) – Compulsory Information

Presentation: Beyfortus 50 mg and 100 mg solution for injection in pre-filled syringe containing 50 mg of nirsevimab in 0.5 mL (100 mg/mL) and 100 mg of nirsevimab in 1 mL (100 mg/mL) respectively. Nirsevimab is a human immunoglobulin G1 kappa (IgG1K) monoclonal antibody produced in Chinese hamster ovary (CHO) cells by recombinant DNA technology. This medicine contains 0.1 mg of polysorbate 80 (E433) in each 50 mg (0.5 mL) dose and 0.2 mg in each 100 mg (1 mL) dose.
Indication: Prevention of Respiratory Syncytial Virus (RSV) lower respiratory tract disease in neonates and infants during their first RSV season, and children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season. Beyfortus should be used in accordance with official recommendations. Dosage and administration: For infants during their first RSV season, the recommended dose is a single dose of 50 mg for infants with body weight <5 kg or 100 mg for infants ≥5 kg, administered intramuscularly. Beyfortus should be administered from birth for infants born during the RSV season. For others born outside the season Beyfortus should be administered ideally prior to the RSV season. Dosing in infants with a body weight from 1.0 kg to <1.6 kg is based on extrapolation, no clinical data are available. Exposure in infants <1 kg is anticipated to yield higher exposures than in those weighing more. The benefits and risks of nirsevimab use in infants <1 kg should be carefully considered. There are limited data available in extremely preterm infants (Gestational Age [GA] <29 weeks) less than 8 weeks of age. No clinical data available in infants with a postmenstrual age (gestational age at birth plus chronological age) of less than 32 weeks. For children who remain vulnerable to severe RSV disease through their second RSV season, the recommended dose is a single dose of 200 mg given as two intramuscular injections (2 x 100 mg).
Beyfortus should be administered ideally prior to the start of the second RSV season. For individuals undergoing cardiac surgery with cardiopulmonary bypass, an additional dose may be administered as soon as the individual is stable after surgery to ensure adequate nirsevimab serum levels. If within 90 days after receiving the first dose of Beyfortus, the additional dose during the first RSV season should be 50 mg or 100 mg according to body weight, or 200 mg during the second RSV season. If more than 90 days have elapsed since the first dose, the additional dose could be a single dose of 50 mg regardless of body weight during the first RSV season, or 100 mg during the second RSV season, to cover the remainder of the RSV season. Safety and efficacy in children 2-18 years not established.
Beyfortus is for intramuscular injection only, preferably in the anterolateral aspect of the thigh. Gluteal muscle should not be used routinely due to risk of sciatic nerve damage. If two injections are required, different injection sites should be used. Contraindication: Hypersensitivity to the active substance or to any of the excipients. Warnings and precautions: To improve traceability of biological medicinal products, record the name and batch number. Serious hypersensitivity reactions, have been reported following Beyfortus administration. Anaphylaxis has been observed with human immunoglobulin G1 (IgG1) monoclonal antibodies. If signs and symptoms of anaphylaxis or other clinically significant hypersensitivity reaction occur, immediately discontinue administration and initiate appropriate medicinal products and/or supportive therapy. As with any other intramuscular injections, nirsevimab should be given with caution to individuals with thrombocytopenia or any coagulation disorder. In some immune compromised children with protein-losing conditions, a high clearance of nirsevimab has been observed in clinical trials, and nirsevimab may not provide the same level of protection in those individuals. This medicine contains 0.1 mg of polysorbate 80 in each 50 mg (0.5 mL) dose and 0.2 mg in each 100 mg (1 mL) dose. Polysorbates may cause allergic reactions. Interactions: Nirsevimab can be given concomitantly with childhood vaccines. Nirsevimab should not be mixed with any vaccine in the same syringe or vial. When administered concomitantly with injectable vaccines, they should be given with separate syringes and at different injection sites. Fertility, Pregnancy and Lactation: Not applicable. Undesirable effects: Adverse reactions reported in clinical trials are uncommon: rash, injection site reaction, and pyrexia. For a complete list of undesirable effects please refer to the Summary of Product Characteristics. Health care professionals are asked to report any suspected adverse reactions via their national reporting system. Marketing Authorisation Holder: Sanofi Winthrop Industrie, 82 avenue Raspail, 94250 Gentilly, France. Legal Classification of the medicinal product regarding medical prescription: Prescription Only Medicine. Date of last review: 25.04.2025.

Abbreviated Prescribing Information based on the EU SmPC as of April 2025.
Before prescribing the product always refer to your full local prescribing information as this information may vary from country to country.

SWEDEN: Beyfortus (nirsevimab). Rx, EF, J06BD
For complete prescriber information, see www.fass.se. Contact details: Beyfortus is provided by Sanofi AB. Box 300 52, 10425 Stockholm, tel +46 8 634 50 00. For questions about our medicines, contact: infoavd@sanofi.com. Date of revision of the summary of product characteristics: 04/2025

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MAT-BE-2501419 v1.0-02/2026