What has changed in the RSV prevention landscape?

A version of this article originally appeared on Contemporary Pediatrics.

Respiratory syncytial virus (RSV), which was first discovered in 1956, has posed a longstanding challenge for vaccine development, particularly in children. Healthcare providers have largely relied on symptomatic management and basic preventative measures such as handwashing, limiting contact with sick individuals during the newborn period, and promoting breastfeeding.

Although the drug palivizumab (Synagis) has been available for high-risk infants, RSV continues to claim the lives of thousands of individuals each year in the United States, including 100 to 300 children. The virus remains a leading cause of respiratory-related hospitalizations, with an estimated 58,000 to 80,000 admissions annually, and virtually all children contract RSV at least once by the age of 2 years.

Before the COVID-19 pandemic, RSV typically followed a predictable seasonal pattern, starting in mid-fall and lasting through winter and early spring in temperate climates. However, during the pandemic, because of various public health measures like physical distancing and mask use, the typical RSV season did not materialize in 2020 or 2021.

Instead, there were atypical surges in RSV infections in spring and fall of 2022. The expectation is that RSV will return to its typical seasonal pattern in the fall of 2023.

Clinical manifestations of RSV include a range of respiratory symptoms, from rhinorrhea and congestion to more severe conditions like bronchiolitis and pneumonia. Complications such as secondary bacterial infections can also occur.

Babies infected with RSV early in life may be at risk of developing reactive airway disease later. Managing these symptoms often requires hospitalization and supportive care.

Efforts to develop an effective RSV vaccine have faced several challenges. Natural immunity to RSV is neither complete nor long-lasting, necessitating the development of a vaccine that can induce a stronger and more durable immune response.

Early vaccine attempts had safety concerns, and the varying demographics that stand to benefit from vaccination complicate the development process. The goal is to reduce the severity and mortality of RSV infections, but there are multiple clinical endpoints to consider.

Until 2023, only 2 pharmaceutical preventive measures were available: RSV-IGIV and palivizumab. However, these options had limitations, leading researchers to continue their efforts in developing new preventive measures. Several candidate vaccines have been evaluated in recent years.

In 2023, nirsevimab-alip (Beyfortus), a monoclonal antibody, was approved for use in children, providing passive immunization and demonstrating a significant reduction in the risk of medically attended lower respiratory tract infections in infants.

This approach simplifies immunization for infants and offers protection during the crucial RSV season. Implementation challenges include monitoring for escape variants, adjusting to changing disease epidemiology, and ensuring widespread access to this medication.

Additionally, a new RSV vaccine for pregnant women, Abrysvo, was approved in 2023 to prevent RSV-related lower respiratory tract disease in infants. However, this vaccine has some safety concerns related to preterm births and is awaiting further guidance.

Looking ahead, the pipeline for RSV vaccine development includes live-attenuated vaccines for children, mRNA vaccines, and vector-based vaccines. Researchers are also working to address delivery mechanisms for low- and middle-income countries.

While 2023 marks the introduction of new tools to combat RSV, it's clear that a combination of strategies will be necessary to reduce RSV-related morbidity in the years to come.

This article was written with the help of ChatGPT.

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