RSV Vaccine for Infants Clears Clinical Trials

Key Takeaways

A promising single-dose vaccine is in development for the prevention of RSV in infants.
Almost all kids are exposed to RSV by the second year of life and most children experience mild symptoms and recover on their own within 1–2 weeks.
Premature infants, as well as those with chronic lung and heart disease are at a high risk for a severe RSV illness.

Last fall, experts warned about the potential triple threat of COVID-19, flu, and respiratory syncytial virus (RSV) cases in kids. Now, a new vaccine is showing promise at protecting infants from the latter.

Phase 3 clinical trial results, published in the New England Journal of Medicine, show that a single dose of nirsevimab, a promising new immunization to treat RSV, was 74.5% effective at warding off the virus in healthy infants. This trial is paving the way for an RSV vaccination to finally become available to the general public. 

The vaccination, which is being developed by Sanofi and AstraZeneca, is a long-acting monoclonal antibody synthetically created to target RSV infections, which can cause bronchiolitis and pneumonia. Phase 2 clinical trials already showed that the treatment was effective in high-risk infants. These new results show it offers protection in healthy infants, too.

But experts aren't convinced that all infants will need this vaccine if it becomes available.

"This is a great new advancement for infants that are preterm or have lung disease," David Cornfield, MD, professor of pediatric pulmonary medicine at Stanford University, told Verywell. "This vaccine should target the high-risk population."

Who Is at Risk for RSV?

RSV is a common, highly contagious seasonal respiratory virus resulting in mild, cold-like symptoms that typically subside in a week or two for healthy children and adults. However, it can be dangerous for infants and elderly adults that are at a higher risk for lower respiratory tract infections.

RSV is also the most common cause of pneumonia and bronchiolitis in infants during their first year of life, resulting in an increase in hospitalizations, and possible death for high-risk children.

Children at high risk for developing complications from an RSV infection include:

Premature infants
Younger than 6 months of age
Chronic lung disease
Congenital heart disease
Weakened immune system
Neuromuscular disorders, which can cause difficulty swallowing or clearing secretions

During the heart of the COVID-19 pandemic in 2020, there was a reported 98% reduction in RSV cases around the world due to mandatory pandemic safety precautions. However, off-season RSV cases spiked during the summer of 2021, logically due to the easing of pandemic restrictions.

This spike came with a warning from infectious disease experts that the absence of RSV in 2020 now puts infants and toddlers at an increased risk for severe RSV-associated illness due to a decrease in virus exposure.

How RSV Is Currently Treated 

RSV is a common virus that most children are exposed to within their first two years of life, and the majority of healthy infants have mild symptoms and go on to make a full recovery in a week or two. Most cases don't require medical treatment and symptoms can be treated at home.

For high-risk infants, palivizumab is currently used to help prevent severe RSV illness and complications. The monoclonal antibody treatment is given as an intramuscular injection once a month over the course of the RSV season.

While this treatment can be effective for limiting hospitalizations and severe illness in infants with high-risk comorbidities, it can be cumbersome and time-consuming for parents.

Is an RSV Vaccine Needed in Healthy Infants?

While an effective single-dose vaccine is highly warranted for high-risk infants, experts question if a vaccine is necessary for healthy infants, since they typically experience mild symptoms and recover on their own.

"I'm not convinced of the need to give this medication to late-term or healthy infants," Cornfield said. "It will be expensive, and may come with uncertain and unintentional consequences."

One of those consequences could be a disruption to what is known as the "hygiene hypothesis," which concludes that children need to be exposed to many viruses in their early years of life to help build a strong and healthy immune system that will benefit their health as they grow older.

An introduction of an RSV vaccine to otherwise healthy infants can lead to a missed opportunity for them to build natural immunity to RSV and similar viruses.

"What would happen when these kids turn three or four, and their body is challenged with other infections?" Cornfield said.

What's Next?

As the RSV vaccine goes through the Advisory Committee on Immunizations Practices (ACIP) and subsequent Food and Drug Administration (FDA) approval processes, there are steps that all parents can take to help prevent the spread of RSV in both infants and elderly adults, and many of them are inline with COVID-19 safety precautions.

The Centers for Disease Control and Prevention (CDC) recommends the following steps to prevent the spread of RSV:

Cover coughs and sneezes with a tissue or your upper shirt sleeve, not your hands
Avoid close contact with others
Don't share cups or eating utensils with others
Disinfect frequently used surfaces
Wash your hands often with soap and warm water
Keep people with cold symptoms away from high risk individuals

As COVID precautions continue to be lifted, it is always a good idea to be vigilant and mindful in practicing social-distancing and good hand hygiene to help prevent the spread of all infectious diseases, not just COVID-19.

What This Means For You

If you have an infant that is at high risk for a severe RSV infection, talk to your pediatrician about a prevention treatment plan.

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