Studied across a broad range of infant populations entering their first respiratory syncytial virus (RSV) season1
*During Trial 04, the COVID-19 pandemic interrupted trial enrollment. The efficacy analysis is based on the Primary Cohort, which included those participants enrolled prior to the pause due to COVID-19. Trial 04 continued monitoring the Primary Cohort and included an additional 1,522 subjects enrolled after the pause to comprise the full study cohort.4
†For neonates and infants in their first season, the recommended dosage is 50 mg for infants <5 kg or 100 mg for infants ≥5 kg via IM injection. For children up to 24 months of age who remain at increased risk for severe RSV disease in their second season, the recommended dosage is a single 200 mg dose administered as 2 IM injections (2 x 100 mg).1
‡Included 128 preterm infants born at <29 wGA.1
Proven strong and consistent efficacy against RSV disease1
Trial 04 (Primary Cohort): healthy term and late preterm infants (≥35 wGA)1*†‡
Primary endpoint: incidence of MA RSV-LRTI through 150 days post 1 dose.
Medically attended (MA) includes all healthcare provider visits such as physician’s office, urgent care, emergency room, and hospitalizations.
Signs of LRTI involvement included rhonchi, rales, crackles, or wheezing and at least one sign of worsening clinical severity, including at least one of the following: increased respiratory rate, hypoxemia, acute hypoxic or ventilatory failure, new onset apnea, nasal flaring, retractions, grunting, or dehydration due to respiratory distress.
CI, confidence interval; LRTI, lower respiratory tract infection; RRR, relative risk reduction.
*Primary Cohort: 1,490 healthy term and late preterm infants (≥35 wGA) in Trial 04.1
†The primary efficacy analysis for Trial 04 is based on infants from the Primary Cohort.1
‡Efficacy for MA RSV-LRTI based on RRR against placebo adjusted for age at randomization.1
Randomized, double-blind, placebo-controlled, multicenter Trial 041,5,6
Baseline characteristics: at randomization, 14% were ≥35 to <37 wGA; 86% were ≥37 wGA.1
PCR, polymerase chain reaction.
*Signs of LRTI involvement included rhonchi, rales, crackles, or wheezing and at least one sign of worsening clinical severity, including at least one of the following: increased respiratory rate, hypoxemia, acute hypoxic or ventilatory failure, new onset apnea, nasal flaring, retractions, grunting, or dehydration due to respiratory distress.1
LRTIs associated with RSV5
Study design with efficacy monitoring for 151 days and safety monitoring for 361+ days6
Post-dose follow-up visits: Day 151 was an efficacy evaluation;
Days 361 and 511 were both safety evaluations entering the second season; final assessment via telephone call.
Beyfortus in RSV hospitalizations compared with placebo1,7
Trial 04: incidence of RSV-LRTI requiring hospitalization through 150 days post 1 dose
RSV hospitalization was defined as hospitalization for LRTI with a positive RSV test.1
Primary Cohort: hospitalization endpoint1,7
The Primary Cohort of Trial 04 included 1,490 infants randomized to receive Beyfortus (n=994) or placebo (n=496)
RRR based on a comparison of infants hospitalized7:
6 infants receiving Beyfortus (0.6%)
8 infants receiving placebo (1.6%)
Full study cohort: exploratory post hoc analysis of the hospitalization endpoint4,7,8
Trial 04 continued to enroll infants following the primary analysis; the full study cohort included 3,012 infants randomized to receive Beyfortus (n=2,009) or placebo (n=1,003) in this post hoc analysis
RRR based on a comparison of infants hospitalized:
9 infants receiving Beyfortus (0.4%)
20 infants receiving placebo (2.0%)
The dose given was 50 mg for infants <5 kg or 100 mg for infants ≥5 kg via IM injection1
- Most common adverse reactions with Beyfortus were rash (0.9%) and injection site reactions (0.3%)1
Proven strong and consistent efficacy against RSV disease1
Trial 03: healthy preterm infants (≥29 to <35 wGA)1*†
Primary endpoint: incidence of MA RSV-LRTI through 150 days post 1 dose
Medically attended (MA) includes all healthcare provider visits such as physician’s office, urgent care, emergency room, and hospitalizations.
Signs of LRTI involvement included rhonchi, rales, crackles, or wheezing and at least one sign of worsening clinical severity, including at least one of the following: increased respiratory rate, hypoxemia, acute hypoxic or ventilatory failure, new onset apnea, nasal flaring, retractions, grunting, or dehydration due to respiratory distress.1
*1,453 preterm infants (≥29 to <35 wGA) in Trial 03.1
†Efficacy for MA RSV-LRTI based on RRR against placebo adjusted for age at randomization and hemisphere.1
Randomized, double-blind, placebo-controlled, multicenter Trial 031,9
Baseline characteristics: at randomization, 20% were ≥29 to <32 wGA; 80% were ≥32 to <35 wGA.1
*Signs of LRTI involvement included rhonchi, rales, crackles, or wheezing and at least one sign of worsening clinical severity, including at least one of the following: increased respiratory rate, hypoxemia, acute hypoxic or ventilatory failure, new onset apnea, nasal flaring, retractions, grunting, or dehydration due to respiratory distress.1
Study design with efficacy monitoring for 151 days and safety monitoring for 361 days10
Post-dose follow-up visits: Day 151 was an efficacy evaluation;
Day 361 was a safety evaluation entering second season.
Beyfortus demonstrated consistent safety profile across multiple healthy infant cohorts1,2,5,9
Trial 04 and Trial 03 were pooled to evaluate the safety of Beyfortus (N=2,570) compared to placebo (N=1,284).1
- Adverse reactions were reported in 1.2% of infants who received Beyfortus; most (97%) of adverse reactions were mild to moderate in severity1
Most Common Adverse Reactions Reported at an Incidence Higher Than Placebo in the Safety Population (Trial 04 and Trial 03)1*
| Adverse reaction | Beyfortus N=2,570 | Placebo N=1,284 |
| Rash† (occurring within 14 days post dose) | 0.9% | 0.6% |
| Injection Site Reaction‡ (occurring within 7 days post dose) | 0.3% | 0.0% |
*The Safety Population includes all infants who received the recommended dose of Beyfortus in Trials 04 and 03: Primary and Safety cohorts from Trial 04; infants who weighed <5 kg and who received the recommended dose of Beyfortus (single 50 mg IM dose) in Trial 03.1
†Rash was defined by the following grouped preferred terms: rash, rash macular, rash maculopapular, rash papular.1
‡Injection site reaction was defined by the following grouped preferred terms: injection site reaction, injection site pain, injection site induration, injection site edema, injection site swelling.1
Safety studied in infants and children at higher risk for severe RSV disease1
The safety of Beyfortus was evaluated in Trial 05, a Phase 2/3, randomized, double-blind, palivizumab-controlled, multicenter trial in infants and children at higher risk for severe RSV disease.
First RSV season: infants born at <35 wGA or infants with CLD of prematurity and/or hemodynamically significant CHD
- Adverse reactions reported among Trial 05 infants who received Beyfortus in their first RSV season were similar to those reported in infants who received Beyfortus in Trials 04 and 03
Second RSV season: children up to 24 months with CLD of prematurity and/or hemodynamically significant CHD
- The safety profile of Beyfortus in these children during their second RSV season was consistent with the safety profile of Beyfortus observed during their first RSV season
Trial 05: analysis of Beyfortus vs palivizumab in infants at higher risk of severe RSV disease1,3
First season study design: randomized, double-blind, palivizumab-controlled, multicenter safety study1,3
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Second season study design: randomized, double-blind, palivizumab-controlled, multicenter safety study1,3
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Forty children who received palivizumab in the first RSV season received Beyfortus in their second RSV season; and 42 children received palivizumab in both first and second RSV seasons.1
Baseline characteristics: at randomization, in the preterm cohort, 77 infants (13%) were <29 wGA and 499 (81%) were ≥29 to <35 wGA. In the CLD/CHD cohort, 70% had CLD; 34% had hemodynamically significant CHD; 123 infants (40%) were <29 wGA; 28% were ≥29 to <35 wGA; and 32% were ≥35 wGA.1
*Signs of LRTI involvement included rhonchi, rales, crackles, or wheezing and at least one sign of worsening clinical severity, including at least one of the following: increased respiratory rate, hypoxemia, acute hypoxic or ventilatory failure, new onset apnea, nasal flaring, retractions, grunting, or dehydration due to respiratory distress.1
Exploratory efficacy: in a study of preterm infants (<35 wGA) and those with CLD/CHD, there was a numerically lower incidence of MA RSV-LRTI with Beyfortus compared with palivizumab1,2*
- Trial 05 was not powered for efficacy but efficacy was assessed as a secondary endpoint
- Efficacy was established based on extrapolation of efficacy from Trials 04 and 03 to the population enrolled in Trial 05, based on similar Beyfortus exposures among infants enrolled in Trials 04 and 05
- The clinical significance of these data is not known
There were no cases of MA RSV-LRTI through 150 days in the second RSV season
*Trial 05 was a Phase 2/3, randomized, double-blind, palivizumab-controlled study evaluating the safety of Beyfortus in infants with CLD or CHD and preterm infants (<35 wGA) entering their first RSV season. Children up to 24 months with CLD or CHD could continue in Trial 05 and receive Beyfortus or palivizumab prior to their second RSV season. The efficacy was established based on extrapolation of the efficacy from Trial 04 and Trial 03 to the population enrolled in Trial 05 based on similar Beyfortus exposures among infants enrolled in Trials 04 and 05.1
Discover real-world Beyfortus data.
Study
31,900 infants studied in BEAR11
Observational, retrospective cohort study at Kaiser Permanente Northern California
Study
8,058 infants studied in HARMONIE12
Phase 3b randomized, open-label study
Study
1,616 infants studied in CDC, real-world analysis13,14
1,616 infants studied in CDC, real-world analysis13,14
US-based CDC hospitalization analysis
CDC, Centers for Disease Control and Prevention.
Tested. Trusted. Demonstrated.
Important Safety Information
References: 1. Beyfortus (nirsevimab-alip). Prescribing Information. Sanofi. 2. Domachowske J, Madhi SA, Simões EAF, et al. Safety of nirsevimab for RSV in infants with heart or lung disease or prematurity. N Engl J Med. 2022;386(9):892-894. 3. Domachowske J, Madhi SA, Simões EAF, et al. Safety of nirsevimab for RSV in infants with heart or lung disease or prematurity. N Engl J Med. 2022;386(9)(suppl):1-42. 4. Muller WJ, Madhi SA, Seoane Nuñez B, et al. Nirsevimab for prevention of RSV in term and late-preterm infants. N Engl J Med. 2023;388(16)(suppl):1-40. 5. Hammitt LL, Dagan R, Yuan Y, et al; MELODY Study Group. Nirsevimab for prevention of RSV in healthy late-preterm and term infants. N Engl J Med. 2022;386(suppl):837-846. 6. Hammitt LL, Dagan R, Yuan Y, et al; MELODY Study Group. Nirsevimab for prevention of RSV in healthy late-preterm and term infants. N Engl J Med. 2022;386(9):837-846. 7. Data on File. Sanofi. 8. Muller WJ, Madhi SA, Seoane Nuñez B, et al. Nirsevimab for prevention of RSV in term and late-preterm infants. N Engl J Med. 2023;388(16):1533-1534. 9. Griffin MP, Yuan Y, Takas T, et al. Single-dose nirsevimab for prevention of RSV in preterm infants. N Engl J Med. 2020;383(5):415-425. 10. Griffin MP, Yuan Y, Takas T, et al. Single-dose nirsevimab for prevention of RSV in preterm infants. N Engl J Med. 2020;383(5)(suppl):1-65. 11. Data on File. Effectiveness of nirsevimab in infants against respiratory syncytial virus (RSV) and RSV-related events. Presented at American College of Allergy, Asthma and Immunology Annual Scientific Meeting. October 24-28, 2024. Boston, MA. 12. Drysdale SB, Cathie K, Flamein F, et al. Nirsevimab for prevention of hospitalizations due to RSV in infants. N Engl J Med. 2023;389(26):2425-2435. 13. Moline HL, Toepfer AP, Tannis A, et al. Respiratory syncytial virus disease burden and nirsevimab effectiveness in young children from 2023-2024. JAMA Pediatr. 2025;179(2):179-187. 14. Moline HL, Toepfer AP, Tannis A, et al. Respiratory syncytial virus disease burden and nirsevimab effectiveness in young children from 2023-2024. JAMA Pediatr. 2025;179(2)(suppl):1-40.
