Beyfortus Shows Strong RSV Protection in Infants

Beyfortus (nirservimab) offered strong protection against respiratory syncytial virus (RSV)-related outcomes in infants and young children, according to a recent study published in JAMA Network.

RSV is a leading cause of lower respiratory tract infections (LRTIs) among infants and older adults.

According to the study, each year, RSV leads to approximately 1.4 million hospitalizations and over 13,000 in-hospital deaths worldwide among infants under six months old.

Little boy wearing a medical nebulizer mask.

In the U.S., RSV also causes up to 160,000 hospitalizations and as many as 10,000 deaths annually among adults aged 65 and older, according to the Cleveland Clinic.

To address this public health challenge, Beyfortus, a long-acting monoclonal antibody for infants and young children, was approved by the FDA in July 2023 following clinical trials that demonstrated high efficacy.

RSV prefusion F (RSVpreF), also known as Abrysvo, was also approved in August 2023 for pregnant women between 32 and 36 weeks of gestation to help pass immunity to their babies before birth.

It also protects adults from lower respiratory infections caused by RSV.

A study observed 36,862 participants over two seasons to positively respond to Abrysvo, finding antibody levels of 12.1 one month after vaccination, indicating a strong immune response.

Prior to the approval of Beyfortus, trials reported that the antibody vaccine reduced medically attended RSV cases by 79%, RSV hospitalizations by 81% and severe cases requiring intensive care by 90%.

Another JAMA study published in January found that nearly 80% of infants born during the late 2023 and early 2024 RSV season received protection against the virus with Beyfortus.

While initial trial results were promising, post-licensure or FDA-approved studies are needed to evaluate how well Beyfortus performs in real-world settings, according to researchers of the study.

Questions remain about its long-term impact, effectiveness across diverse populations and its role in preventing milder RSV cases.

To examine further, researchers used a test-negative case-control design to evaluate the real-world clinical effectiveness of Beyfortus in a broad U.S. patient population, examining its protection over time, across different disease severities and at different dosages.

The study included patients born after October 1, 2022, who were tested for RSV due to suspected acute respiratory infections and received care within the Yale New Haven Health System (YNHHS) between October 1, 2023, and May 9, 2024.

YNHHS, Connecticut’s largest health system, is made up of five hospital networks, 30 emergency or urgent care centers and over 130 outpatient clinics across Connecticut, New York and Rhode Island through a unified electronic health record (EHR) system.

Patients were excluded if they were ineligible for Beyfortus when it became available on October 1, 2023, or lived outside the covered states, ensuring accurate immunization records through state registries.

Infants qualified for Beyfortus if they were under eight months entering their first RSV season or between eight and 12 months with at least one severe RSV risk factor.

Out of 3,090 infants, 10.7% (330) received Beyfortus, with 21 RSV-positive cases and 309 RSV-negative controls immunized.

The adjusted effectiveness was 68.4% against medically attended RSV infections, 61.6% for outpatient visits and 80.5% for hospitalizations.

The highest protection (84.6%) was observed against severe RSV disease.

Although effectiveness declined over time from 79.3% at 2 weeks to 54.8% at 14 weeks post-immunization, it remained significant.

Effectiveness was consistent across different doses.

During peak RSV season, the antibody vaccine also reduced all-cause LRTI by 49.4% and LRTI-related hospitalizations by 79.1%.

However, from February to May 2024, when other viruses were more prevalent, its impact on non-RSV LRTIs was minimal.

Researchers suggest several areas for future investigation based on the findings.

They recommend studying the best timing for Beyfortus immunization, especially in regions with long RSV seasons.

Future studies should also explore its impact on outpatient visits and other respiratory illnesses, beyond just hospitalizations.

In addition, larger studies are needed to evaluate dose-specific effectiveness.

Longer-term research is also recommended to assess effectiveness past 14 weeks.

Lastly, exploring barriers to immunization and improving accessibility, mainly for underrepresented groups, is crucial.