Anushua Sinha, MD, MPH, highlights sustained RSV protection from ENFLONSIA

In a recent interview with Contemporary Pediatrics, Anushua Sinha, MD, MPH, Lead Clinical Director for the ENFLONSIA program at Merck, discussed new findings from the SMART trial regarding ENFLONSIA (clesrovimab; Merck), an immunization used to prevent respiratory syncytial virus (RSV) in infants. The conversation focused on the safety, efficacy, and procedural considerations for administering the immunization during a child’s second RSV season, particularly for high-risk populations.

Addressing safety concerns, Sinha noted that when children received ENFLONSIA at the beginning of their second RSV season—following a prior dose of either ENFLONSIA or palivizumab in their first season—the rate of injection site reactions remained perfectly comparable to observations from the first season. Furthermore, immunogenicity—the undesirable development of antibodies against the drug itself—remained low during the second season. Sinha emphasized that researchers are currently conducting extensive analyses on this immunological data to present at future medical conferences.

The interview also explored the strategy of "re-dosing" high-risk toddlers, particularly those undergoing cardiac surgery that requires cardiopulmonary bypass. Because bypass procedures can effectively wash out protective antibodies from a preoperative dose, an additional 105-milligram dose of ENFLONSIA is already indicated for infants in their first RSV season once they stabilize post-surgery to ensure durable protection.

However, for the second season, most infants in the SMART trial who had successful corrective surgeries were technically no longer eligible for ENFLONSIA. Data for the small subset of participants who did receive a second-season re-dosing post-procedure is currently being analyzed.

Sinha clarified that ENFLONSIA is not yet officially indicated for a second-season dose, though Merck intends to file for a supplemental second-season indication soon. Anticipating this future regulatory approval, Sinha addressed potential supply chain anxieties pediatricians might have based on past industry shortages.

She assured viewers that Merck has significantly ramped up its manufacturing efforts over several years. The company is confident in its secure supply chain and its ability to fully meet United States market demand once the product is approved for broader use.

Ultimately, RSV remains the leading reason for infant hospitalizations annually in the United States. Sinha concluded by highlighting that ENFLONSIA provides a crucial, reliable option with a strong safety and efficacy profile. By continuing to advance clinical research through initiatives like the SMART trial, Merck aims to significantly reduce the heavy burden that such as places on infants, their families, pediatric practices, and the broader health care system.

Disclosure: Merck.

This video is part 2 of a 2-part series. Click here for part 1.

Reference

Merck announces positive new data for Enflonsia (clesrovimab) for infants and children under 2 years of age at increased risk for severe respiratory syncytial virus (RSV) disease over two RSV seasons. News release. Merck. February 19, 2026. March 5, 2026. https://www.businesswire.com/news/home/20260219213035/en/Merck-Announces-Positive-New-Data-for-ENFLONSIA-clesrovimab-for-Infants-and-Children-Under-2-Years-of-Age-at-Increased-Risk-for-Severe-Respiratory-Syncytial-Virus-RSV-Disease-Over-Two-RSV-Seasons