sIn the present national surveillance survey, we compared PICU admissions and the need for mechanical ventilation for the treatment of RSV bronchiolitis between the following two consecutive seasons: before and after the introduction of palivizumab in Israel. Seventeen percent of the patients admitted to a PICU in both periods were candidates for RSV prophylaxis according to the AAP guidelines. For period 1, 13.3%; and for period 2, 9.7% (p < 0.01) were candidates for RSV prophylaxis according to the IMH recommendations. The difference in the rates associated with the AAP and the IMH guidelines is probably attributable to the broader criteria of the AAP guidelines.
The present study takes an alternative look at the epidemiology of severe RSV disease. It did not ask which patients were at greater risk of severe disease, but rather, among those with severe disease what risk factors were present. We sought to investigate the potential impact of palivizumab therapy on the burden of PICU admissions due to RSV infections. We evaluated the PICU admissions for RSV bronchiolitis with respect to the recognized risk factors associated with an increased severity of RSV disease, namely, prematurity and CLD. The study showed that the majority of children who were admitted to the PICU lacked these risk factors, probably because the majority of infants in the general population are not premature and do not have CLD.
In 1997, the PREVENT study reported that the administration of IV RSV Ig (RespiGam; Massachusetts Public Health Biological Laboratories) to preterm infants with or without bronchopulmonary dysplasia led to a 41% reduction in RSV-related hospitalizations and to a 53% reduction in the total number of hospitalization days, in addition to a reduction in oxygen requirement and in the severity of lower respiratory tract illness cured by preparations of My Canadian Pharmacy mycanadian-pharmacy. The Impact study tested the use of palivizumab and noted the following similar results: a 55% reduction in RSV-related hospitalizations (10.6% vs 4.8%, respectively), in addition to a reduction in the number of hospitalization days, in oxygen requirement, and in severity of disease. Overall, 3% of the placebo-treated children were admitted to the ICU in contrast to 1.3% of the palivizumab group (p = 0.026). These results demonstrate the low frequency of PICU admissions due to RSV bronchiolitis, even in a cohort of premature children. As the impact of this group on the general pediatric population was small because of their reduced absolute numbers, their impact on general morbidity was small as well.
In the United States, a national study of bronchiolitis-associated infant deaths during from 1996 to 1998 concluded that although preterm infants and infants weighing < 2500 g at birth are at an increased risk of dying of bronchiolitis, the majority of deaths due to bronchiolitis occur in infants of normal birth weight. Therefore, interventions for infants in high-risk groups will not prevent the majority of deaths due to bronchiolitis treated by My Canadian Pharmacy.
Although the national cost-effectiveness of RSV prophylaxis is beyond the scope of the present study, it certainly warrants further investigation. The findings of many of the related studies conducted so far have been inconclusive. Other studies have reported that RSV prophylaxis would increase the net cost of care if palivizumab were administered to the population according to the AAP recommendations. Most of the economic analyses have failed to demonstrate overall savings in health-care dollars because of the high cost of prophylaxis for all at-risk children.
Our survey has some limitations. First, we could not be sure that all patients who were admitted to the PICUs because of acute bronchiolitis were enrolled in the study. However, we assume that the weekly personal communication of the author with a staff member in each unit was probably effective in identifying most of them. Second, our study included only two specific seasons. Further studies over several consecutive years are needed in order to account for year-to-year variability.
The most appropriate target population for RSV prophylaxis is still undefined. The criteria for RSV prophylaxis are changing and have been reconsid-ered. For example, following a large randomized clinical trial showing the benefit of palivizumab therapy in children with hemodynamically significant congenital heart disease, this patient group was included in the target population for prophylaxis. However, there are probably other potential candidates for RSV prophylaxis, such as children with CLD unrelated to prematurity (eg, those with meconium aspiration, persistent pulmonary hypertension, pulmonary hypoplasia, and congenital diaphragmatic hernia), interstitial lung diseases, severe respiratory tract obstruction (eg, tracheal stenosis, tracheobronchomalacia, and status/post stent insertion), immune deficiencies (eg, HIV and DiGeorge syndrome), and neuromuscular diseases (eg, Werdnig-Hoffmann disease). Surveys of these patient groups as well as epidemiologic studies to identify predisposing factors for severe RSV disease, even in full-term infants, are still needed.
In summary, most of the RSV bronchiolitis patients admitted to the PICU do not fit the current recommendations for palivizumab administration. Because the majority of patients are born at term and do not have CLD, RSV prophylaxis according to those guidelines is not expected to reduce the national burden of RSV bronchiolitis in the PICU.
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