On December 9, 2025, the U.S. Food and Drug Administration (FDA) initiated a formal safety review of two widely used monoclonal antibody treatments for respiratory syncytial virus (RSV), Beyfortus and Enflonsia. These medications have been approved and are currently used to prevent severe RSV infections, particularly in vulnerable populations such as infants and older adults, who are most at risk for the serious complications of the virus. This safety review comes as part of the FDA’s routine post-market surveillance procedure, which is triggered whenever new safety data emerges about a treatment after it has been approved and is in use.
Respiratory syncytial virus is a common respiratory infection that can lead to severe illness, especially in young children and elderly adults. For these high-risk groups, the availability of preventive treatments like Beyfortus and Enflonsia has been a significant breakthrough in combating RSV. These monoclonal antibodies work by boosting the body’s immune system to help prevent infection, significantly reducing the likelihood of hospitalization or severe disease progression. Since their approval, both treatments have been widely utilized, saving lives and reducing healthcare burdens.
Despite the positive impact these treatments have had on public health, the FDA’s decision to launch a safety review reflects its ongoing commitment to patient safety. While no direct links to adverse outcomes have been identified thus far, the FDA’s standard procedure involves careful, continued monitoring of biologic therapies as they are used in broader clinical settings. The review will focus on analyzing the most recent clinical data and real-world usage patterns to ensure that these treatments continue to be safe and effective for the individuals who rely on them most.
The safety review process is vital for maintaining the public’s confidence in the treatments they use, particularly when dealing with biologic drugs, which often carry more complex safety profiles than traditional medications. Although these treatments have proven to be beneficial, the FDA wants to ensure that their widespread use continues to meet the highest safety standards. This review will help to assess if there are any emerging risks associated with long-term use or with certain patient populations that might not have been fully understood when the therapies were first approved.
The FDA emphasized that it is undertaking this review not because of any known issues with the drugs, but as part of its ongoing monitoring of the safety and efficacy of treatments in the real world. The agency’s thorough and proactive approach is designed to identify any potential concerns early, ensuring that treatments can be adjusted or recalled if necessary to protect public health. This level of oversight reflects the FDA’s continued focus on ensuring that any biologic or medical therapy remains as safe as possible once it is approved and widely available.
For the public and healthcare providers, it is important to understand that safety reviews are common in the pharmaceutical industry and are an essential part of ensuring that new treatments continue to benefit patients over time. The ongoing review of Beyfortus and Enflonsia will help solidify these drugs’ place in the treatment of RSV and provide critical insights into their long-term use. The FDA will continue to monitor the situation closely, and further updates will be provided as new information becomes available.
This announcement also comes at a time when federal policy decisions are under scrutiny across various sectors, including healthcare and technology. The ongoing safety review is just one example of the FDA’s broader commitment to maintaining high standards of patient care and ensuring that health products on the market remain safe for public use. The outcome of this review will likely have lasting implications for both the treatment of RSV and the broader landscape of biologic therapies, influencing how such treatments are used and monitored in the future.
