Healthy Babies Can Still Get Very Sick From RSV

Marcus A. Banks

August 16, 2023

Any parent might naturally assume that their newborn is at little risk from respiratory syncytial virus (RSV), which in healthy infants has been thought to cause mild symptoms similar to having a cold. But a new study challenges the assumption that only infirm children are at risk for the worst outcomes from RSV, finding that more than 80% of infants hospitalized with the infection were otherwise healthy before they developed the lung disease.

The researchers, who published their study August 15 in JAMA Network Open, said the results reinforce the importance of a new  preventive shot that can lower the risk for severe RSV infection in babies.

Dr Natasha Halasa

"RSV is the number one cause of hospitalizations in young infants," said Natasha Halasa, MD, MPH, an infectious disease specialist at Vanderbilt University Medical Center in Nashville, Tennessee, and the lead author of the new study. But "the vast majority of kids didn’t have underlying medical conditions" when they got sick.

Every infant in the study was in an intensive care unit for at least 24 hours, Halasa said, putting both an emotional and logistical strain on parents who now had to figure out how to maintain work commitments and continue to care for any other children in the family. And most babies gave no prior indication that RSV would affect them so profoundly.

"Two to three of every 100 babies in the United States will be hospitalized for RSV in their first year of life," added study author Angela Campbell, MD, MPH, of the Coronavirus and Other Respiratory Viruses Division of the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. 

Until recently, only one treatment was available for children up to age 2 at high risk for RSV, the monoclonal antibody palivizumab (Synagis). Palivizumab is reserved for children who are born prematurely, are immunocompromised, or have chronic heart or lung disease. The injection is given monthly during the 5-month peak of RSV season, from fall to spring.

In July, the Food and Drug Administration (FDA) approved, and the CDC has since recommended, a new monoclonal antibody called nirsevimab (Beyfortus) to prevent the worst effects of RSV. Nirsevimab is intended for all newborns under age 8 months who were born during the RSV season, or babies who will be entering that season before reaching 8 months. The injection is given only once and can act for 150 days. The FDA and CDC actions came following a clinical trial showing that nirsevimab lowers the risk for hospitalization from RSV among infants by more than 75%.

"We’re very excited that this product exists now," Campbell said.

Chart Reviews During the 'Tripledemic'

In fall 2022 the United States experienced a "tripledemic" of elevated hospitalizations for COVID-19, influenza, and RSV. For the new study, Halasa and her colleagues examined the medical records of 600 infants (under age 1; average age, 2.6 months) admitted to US ICUs for lower respiratory tract infections caused by RSV from October to December 2022, during the height of the tripledemic. 

More than 60% of admissions, 361, were boys; 44% were White, 23% were Hispanic, 16% were Black, 10% were unknown race, 5% were multiple race, and 2% were Asian. 

Of the 600 infants, 572 required oxygen at the hospital (95.3%) and 487 (81.2%) had no underlying medical conditions linked to higher risk from RSV. The other infants had at least one ailment, such as a cardiac or lung condition, that could result in more severe RSV outcomes.

The 169 preemies in the study population were more likely to be intubated in the ICU than those born at term. But 90 of the 143 total recorded intubations happened among full-term infants. Two children in the study group died.

Christopher Horvat, MD, MHA, who works in the pediatric ICU at the University of Pittsburgh Medical Center, called the new study "important," adding that it shows "the RSV burden is substantial for children who are otherwise healthy." Horvat, who was not involved in the work, said the new data highlight the value of preventive measures to prevent any repeat of the tripledemic.

On the same day the new study was published, the American Academy of Pediatrics (AAP) released a statement calling for widespread access to nirsevimab.

"The American Academy of Pediatrics recommends that all infants — and especially those at high risk — receive the new preventive antibody, nirsevimab, to protect against severe disease caused by respiratory syncytial virus (RSV), which is common, highly contagious, and sometimes deadly," the organization said in a statement.

The AAP called for the CDC and the Centers for Medicaid and Medicare Services to work together to ensure that any parent in America can obtain nirsevimab for their children if needed. Anyone who cannot access nirsevimab this year, the AAP said, should rely on the older treatment palivizumab instead.

The sources in this story report no relevant financial relationships.

JAMA Netw Open. Published August 15, 2023. Full text.

Marcus A. Banks, MA, is a journalist based in New York City who covers health news with a focus on new cancer research. His work appears in Medscape, Cancer Today, The Scientist, Gastroenterology & Endoscopy News, Slate, TCTMD, and Spectrum.

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