Sanofi US News

Sanofi Beyfortus™ (nirsevimab-alip) Injection Update

December 14, 2023

Sanofi and our partner AstraZeneca continue to engage with government officials, healthcare providers and others in the U.S. regarding supply of Beyfortus™ (nirsevimab-alip) 50mg and 100mg Injection.

Since we launched in September, hundreds of thousands of infants in the U.S. have received Beyfortus. This is the first season in which an immunization for babies against respiratory syncytial virus has been provided on such a broad scale.

Given the high demand for Beyfortus, and questions about how we prepared for this first season, we’re providing additional information about our planning and next steps.

We benchmarked our estimates for this introductory season of Beyfortus on the launches of two successful, innovative pediatric immunizations: rotavirus vaccine and pneumococcal conjugate vaccine. While there was no perfect analogue for Beyfortus, these represented the most relevant launch comparators. Rotavirus vaccine and pneumococcal conjugate vaccine, respectively, had about 10 percent and 11 percent immunization rates in their first 6 months of launch. Our research indicated that exceptional demand for Beyfortus could lead to uptake by as much as 30 percent of the birth cohort in the first six months, far outpacing those two analogues.

As we planned for launch, stakeholders in the immunization community indicated that we might face challenges with implementation and uptake due to the unique nature of Beyfortus (a novel monoclonal antibody). This included issues such as timing of payer coverage and coding.

Nevertheless, we took an aggressive outlook and aimed to provide Beyfortus to 30 percent of the birth cohort within 6 months of launch, coinciding with the RSV season. In all, this plan projected a total of 1.1 million doses for the U.S.

Due to the long lead times needed by manufacturer AstraZeneca to produce a monoclonal antibody, our estimates for the launch supply of Beyfortus had to be finalized in March 2023.

As we began launching, we saw signals that some implementation barriers, including commercial payer coverage and coding issues, were resolving faster than expected.

Within two weeks of the start of shipping in late September, orders exceeded the planned available doses for the season, with orders for 100mg doses outpacing supply. We immediately contacted the Centers for Disease Control and Prevention (CDC) to coordinate the impact on the Vaccines for Children program and on the private market.

Since early October, we have been working closely with the CDC and Food and Drug Administration to deliver additional doses this season and holding weekly touchpoints since November. We have also welcomed engagement with the CDC, the Office of Pandemic Preparedness and Response (OPPR) and other Health and Human Services and White House officials through regular meetings.

These partnerships and the efforts of both companies have resulted in an additional 77,000 100mg doses being made available, and we plan to provide approximately 230,000 additional doses - made up of 50mg and 100mg doses - for the U.S. in January. This would bring the first season to an immunization rate of nearly 40 percent, which greatly surpasses prior launches of a pediatric immunization and represents a total of 1.4 million babies offered protection against RSV, a 27 percent increase over the initial supply forecast  for the season.

While the interest in and demand for Beyfortus have been unprecedented, we acknowledge the weight of this situation – both for caregivers and healthcare providers - and have started to plan accordingly for next season. This includes Sanofi and AstraZeneca working to augment the manufacturing network for Beyfortus, closely partnering with stakeholders in the immunization community to project demand and implementing a process in February to support providers and others planning for the 2024/25 RSV season. 

Sanofi is a leading force in the fight against infectious disease. We supply about 1 billion immunizations against different diseases every year around the world. Our legacy is intertwined with disease prevention and underpinned by the knowledge that immunizations are among the most significant advances in public health in human history.

We will continue to coordinate with government agencies and providers in the U.S. as we move forward with the collective ambition to protect as many babies as possible against RSV.


Beyfortus is a prescription medicine used to help prevent a serious lung disease caused by Respiratory Syncytial Virus (RSV) in:

  • Newborns and babies under 1 year of age born during or entering their first RSV season.
  • Children up to 24 months of age who remain at risk of severe RSV disease through their second RSV season.


Your child should not take Beyfortus if your child has a history of serious allergic reactions to nirsevimab-alip or any of the ingredients in Beyfortus.

Before your child receives Beyfortus, tell your healthcare provider about all of your child’s medical conditions, including if your child:

  • has ever had a reaction to Beyfortus.
  • has bleeding or bruising problems. If your child has a problem with bleeding or bruises easily, an injection could cause a problem.

Tell your healthcare provider about all the medicines your child takes, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Your infant should not receive a medicine called palivizumab if they have already received Beyfortus in the same RSV season.

Serious allergic reactions have happened with other medicines like 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 the possible side effects of Beyfortus. Call your healthcare provider if you have questions about side effects.

Please see full Prescribing Information, including Patient Information for more details.

About Sanofi

We are an innovative global healthcare company, driven by one purpose: we chase the miracles of science to improve people’s lives. Our team, across some 100 countries, is dedicated to transforming the practice of medicine by working to turn the impossible into the possible. We provide potentially life-changing treatment options and life-saving vaccine protection to millions of people globally, while putting sustainability and social responsibility at the center of our ambitions.

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Media Relations

Evan Berland | +1 215 432 0234 |