Risk factors for severe respiratory syncytial virus infection in infants

Palivizumab prophylaxis reduces hospitalization due to respiratory syncytial virus in young children with hemodynamically significant congenital heart disease

OBJECTIVES

To evaluate the safety, tolerance, and efficacy of palivizumab in children with hemodynamically significant congenital heart disease (CHD).

STUDY DESIGN

A randomized, double-blind, placebo-controlled trial included 1287 children with CHD randomly assigned 1:1 to receive 5 monthly intramuscular injections of 15 mg/kg palivizumab or placebo. Children were followed for 150 days. The primary efficacy end point was antigen-confirmed respiratory syncytial virus (RSV) hospitalization.

RESULTS

Palivizumab recipients had a 45% relative reduction in RSV hospitalizations (P=.003), a 56% reduction in total days of RSV hospitalization per 100 children (P=.003), and a 73% reduction in total RSV hospital days with increased supplemental oxygen per 100 children (P=.014). Adverse events were similar in the treatment groups; no child had drug discontinued for a related adverse event. Serious adverse events occurred in 55.4% of palivizumab recipients and 63.1% of placebo recipients (P<.005); none were related to palivizumab. Twenty-one children (3.3%) in the palivizumab group and 27 (4.2%) in the placebo group died; no deaths were attributed to palivizumab. The rates of cardiac surgeries performed earlier than planned were similar in the treatment groups.

CONCLUSIONS

Monthly palivizumab (15 mg/kg IM) was safe, well-tolerated, and effective for prophylaxis of serious RSV disease in young children with hemodynamically significant CHD.

Current strategies in the prevention of respiratory syncytial virus disease

Infants infected with respiratory syncytial virus (RSV) develop both upper and lower respiratory tract infections resulting in laryngotracheobronchitis, bronchiolitis and pneumonia. Premature infants of less than 32 weeks' gestation and those with underlying chronic lung disease are particularly susceptible and incur significant morbidity and mortality following hospitalisation. Conservative RSV prevention strategies focus on the interruption of transmission by proper hand-washing techniques and reducing exposure to potential environmental risk factors. Major challenges have impeded the development of an RSV vaccine but a licensed product may be expected in the near future. Prophylaxis with a humanised mouse monoclonal antibody (palivizumab) has been effective in reducing the rate of RSV hospitalisation in high-risk premature infants in phase II-IV trials and is available for use within internationally approved guidelines. Experimental studies evaluating the use of palivizumab in patients with congenital heart disease, those with cystic fibrosis and immunosuppressed bone marrow transplant recipients are well underway, the results of which are eagerly awaited.

Populations at risk for developing respiratory syncytial virus and risk factors for respiratory syncytial virus severity: infants with predisposing conditions

According to National Vital Statistics Reports, premature infants (< 36 weeks gestation) account for approximately 7.4% of all births. During the 8 years from 1989 to 1997, multiple births steadily increased across all categories from twin to quintuplet and higher orders. During that same period low birth weight (< 2500 g) births increased almost 12%, and very low birth weight (< 1500 g) births increased approximately 20%.Attendant to these national trends in multiple and preterm births, overall gestation-specific survival rates have improved substantially. This improved outcome can be attributed in large measure to advances in neonatal care and technology. Despite the encouraging statistics on survival, infants born prematurely, at low or very low birth weights and/or with chronic conditions that predispose to lower respiratory tract illness, continue to incur serious risk of long term morbidity and the consumption of inpatient hospital services. In a recent 2-year study of US children, low and very low birth weights were found to be independent risk factors for bronchiolitis-associated mortality. In the past 14 years what defines bronchopulmonary dysplasia (BPD)/chronic lung disease (CLD) has shifted away from clinical, radiographic and pathologic findings in the preterm infant toward the pathophysiology of arrested lung development and the need for supportive care beyond 36 weeks corrected gestational age. The incidence of BPD/CLD ranges from 14 to 43%, with higher rates observed among infants of lower gestational age and birth weight. The health care team approach to the management of BPD directs its efforts toward minimizing pulmonary vascular resistance, alleviating airway obstruction and improving short term lung mechanics. Measures to prevent BPD/CLD attempt to forestall both acute and chronic lung function abnormalities. To that end researchers have investigated the early use of continuous positive airway pressure, vitamin supplementation and recombinant human copper/zinc superoxide dismutase. Despite significant gains in the survival of infants born at lower gestational ages, prematurity, low birth weight and/or underlying chronic pulmonary disease put the pediatric patient at risk for increased frequency and severity of respiratory syncytial virus lower respiratory tract illness and the potential for its long term sequelae.