Reducing RSV risk in preemies: Here's how

November 21, 2005

According to the National Center for Health Statistics, premature births are at a record high. Combine that fact with the reality of the crowded living conditions in the wake of recent hurricanes and we may have a recipe for respiratory syncytial virus (RSV) disaster this coming season.

According to the National Center for Health Statistics, premature births are at a record high. Combine that fact with the reality of the crowded living conditions in the wake of recent hurricanes and we may have a recipe for respiratory syncytial virus (RSV) disaster this coming season.

So said neonatologists and infectious disease (ID) specialists from Children's Hospital Boston at a recent press briefing. The experts urged pediatricians and parents-not only in hurricane-stricken areas, but all across the United States-to protect premature infants during the upcoming virus season.

"RSV and other common respiratory illnesses cause only minor symptoms in most children, but they can lead to more serious illnesses for our smallest and most vulnerable babies," said Kenneth McIntosh, M.D., an infectious disease specialist at Children's Hospital and a professor of pediatrics at Harvard Medical School. According to the American Academy of Pediatrics (AAP), infants most at risk for RSV are those born at a gestational age of less than 36 weeks, infants with chronic lung or heart disease, and those with a compromised immune system.

"Once a premature baby gets RSV, there's little we can offer but supportive therapy, which may mean a return to the hospital and possibly mechanical ventilation," said Marcia L. Buck, Pharm.D., FCCP, a clinical pharmacy specialist at the University of Virginia's Children's Medical Center. "Along with rehospitalization comes the need for intravenous lines, IV fluids, and/or parenteral nutrition, and other medications-all of which increase the risk for infection and other complications."

The physicians at the press briefing also encouraged the use of RSV-prevention medication-namely, palivizumab (Synagis, MedImmune)-to reduce the risk of severe infection. They noted that palivizumab, a humanized monoclonal antibody to RSV, can give high-risk infants a jump start on fighting off severe infection by helping to compensate for preemies' low levels of maternal antibodies. The biologic does not guarantee that the child will not become infected with RSV, they explained, but it can make symptoms milder.

"Palivizumab inhibits both the activity of RSV and its replication," explained Buck. "It has a mean elimination half-life of approximately 20 days, so it must be administered once a month during the RSV season to maintain adequate serum concentrations."

According to the manufacturer, palivizumab should be injected intramuscularly at a dosage of 15 mg/kg once a month from November to April. The drug binds to a specific protein, the fusion or F-protein, preventing the virus from infecting host respiratory cells and reducing RSV replication and spread to other cells.

"Preventive therapy with palivizumab appears to lower the risk for severe disease in susceptible patients," Buck said. In the IMpact-RSV trial, there was a 55% overall reduction in hospitalization in premature infants receiving the agent she added. "A similar benefit has been shown in babies with underlying congenital heart disease."

The experts warned that patients can be infected with RSV more than once because immunity produced by the infection is incomplete and temporary. Currently, no vaccine exists for RSV prevention.

Pharmacists can help identify patients who meet the AAP criteria for use of palivizumab, concluded Buck. "If you are providing care for an infant or toddler who is receiving chronic pulmonary therapies, such as a bronchodilator, or medications for heart disease, these patients are likely to benefit" from preventive treatment.

The Children's Hospital press briefing was underwritten by MedImmune and can be accessed at http://www.childrenshospital.org/.