About half of all babies younger than a year become infected by the respiratory syncytial virus (RSV), which causes the most common form of respiratory infection of infancy. Almost all toddlers get the virus before their second birthday. In otherwise healthy kids, symptoms are mild and similar to the common cold. Usually, no medical intervention is necessary. In some children, though, an RSV infection can be quite serious. These kids are much more likely to spend time in a hospital due to RSV during the first six months of their lives than most kids.

Children born prematurely, especially those with chronic lung disease (CLD) of prematurity, are highly vulnerable to RSV infection, as are children with some forms of congenital heart disease. Other factors contribute to the severity of RSV infection as well.

Influenza and RSV are alike in various ways:

  • They’re both viral infections that cause similar respiratory distress.
  • They’re seasonal. Flu season in the US runs, roughly, from October through March while RSV season runs from November to March.
  • There are prophylactic (prevention) measures to decrease the risk of illness. Influenza vaccination (flu shots) greatly reduces the risk of getting the flu; injections of an RSV-prevention drug — palivizumab — administered once a month to high-risk infants during RSV season can greatly reduce their risk of infection and, subsequently, hospitalization.

The value of RSV prophylaxis for preemies was documented in a recent study led by Dr. Eric Simões of the University of Colorado. The study involved 1,642 infants younger than six months who were treated for acute respiratory illness at emergency rooms and hospitals at 188 US medical facilities. All the children were born prematurely and were younger than six months on November 1 in 2009 or 2010.

Of this study group, 287 tested positive for RSV. The children most at risk for hospitalization:

  • Were born at 32 through 34 weeks gestational age (wGA)
  • Were born at 35 wGA and attended daycare
  • Were born at 35 wGA and were younger than 3 months when RSV season began
  • Had at least one older sibling of preschool age

These risk factors are recognized by the American Academy of Pediatrics (AAP), which recommends RSV prophylaxis therapy for all infants who have one or more of these risk factors. When none of these risk factors is present, the AAP does not recommend prophylaxis, even for otherwise healthy preemies born 32 to 34 wGA.

Of the children treated in the study, 13% were eligible for prophylaxis but did not get even one dose of palivizumab. The children who did not get palivizumab were more likely to:

  • Be African American or Hispanic
  • Have been born weighing more than 1,500 grams (3.3 pounds)

Of all the children in the study, the rate of hospitalization for RSV was almost three times higher (4.9%) than the rate of hospitalization for any reason for a child younger than six months. Sixteen percent of these babies hospitalized because of RSV were admitted to an intensive care unit (ICU) for RSV disease and 11% required mechanical ventilation.

Source: Simões, Eric A, et al. “Respiratory Syncytial Virus Disease in Preterm Infants in the US Born at 32-35 Weeks Gestation Not Receiving Immunoprophylaxis.” The Pediatric Infectious Disease Journal. Lippincott Williams & Wilkins. Jun 2014. Web. Jun 17, 2014.