Effect of palivizumab prophylaxis in decreasing respiratory syncytial virus hospitalizations in premature infants

BACKGROUND: Respiratory syncytial virus (RSV) is a major cause of hospitalization in preterm infants and infants with chronic lung disease (CLD). Palivizumab, a humanized monoclonal antibody, was approved in Europe in 1999 as prophylaxis against severe RSV-related respiratory illness. No multiple season data have been published on palivizumab effectiveness in European populations. Data collected during 4 years in Spain compared RSV hospitalization rates and risk factors in a cohort of palivizumab-prophylaxed and nonprophylaxed preterm infants. METHODS: The first cohort was derived from 2 previous studies and included 1583 infants followed during 2 RSV seasons (1998 to 1999, 1999 to 2000) before palivizumab initiation in Spain. The second cohort included 1919 infants who received palivizumab prophylaxis for 2 subsequent respiratory seasons (2000 to 2001, 2001 to 2002). Both cohorts were preterm (< or =32 weeks gestational age) and < or =6 months old at onset of RSV season. RESULTS: The RSV hospitalization rate in the palivizumab-prophylaxed cohort was 3.95, and it was 13.25% in nonprophylaxed infants This 70% overall difference in RSV hospitalization was observed despite the palivizumab-prophylaxed group's lower gestational ages, more severe neonatal intensive care unit respiratory courses and higher incidence of CLD. Significant risk factors for RSV hospitalization in both cohorts included: lower gestational age; chronologic age <3 months at RSV season onset; school age siblings; and lower parental education. Nonprophylaxed children had a higher risk for RSV-related hospitalization than did prophylaxed patients (odds ratio, 3.86; 95% confidence interval, 2.83 to 5.25). CONCLUSION: Data from this study support the effectiveness of palivizumab in significantly modifying RSV-related hospitalizations in high risk preterm infants, with and without CLD, during two respiratory seasons.     

Survey of pediatric ward hospitalization due to respiratory syncytial virus infection after the introduction of palivizumab to high‐risk infants in Japan

Background: Respiratory syncytial virus (RSV) infection is a major cause of hospitalization during the winter among infants and young children. In 2002 palivizumab was introduced to high‐risk infants for RSV hospitalization in Japan. It is important to characterize the hospitalized children due to RSV infection after the introduction of palivizumab. Methods: A survey was conducted to collect the data from the hospitalized children at 12 participating hospitals during the winter of 2007. Results: From October 2007 through April 2008, 8163 children were admitted to participating hospitals, with RSV infection accounting for 811 of those hospitalizations. Mean age in children with RSV infection at hospitalization was 12.4 ± 12.7 months, and children under 24 months of age accounted for 86.4%. The mean gestational age of those at birth was 38.0 ± 2.6 weeks, with 82.4% of the children born at term. Palivizumab was administered in 24 cases of RSV infection, while there were 28 patients who were not treated with palivizumab, even though they met the indication for palivizumab. Death, in a total of five cases, occurred in children who were not treated with palivizumab. Conclusions: Palivizumab has been widely used in high‐risk infants who were covered by health insurance, and most of the hospitalized children with RSV infection in the study hospitals were not treated with palivizumab.     

Prophylaxis of respiratory syncytial virus (RSV) in preterm infants with/without bronchopulmonary dysplasia: hyperimmune globulin (RSV-IGIV) and palivizumab (MEDI-493)

Respiratory syncytial virus (RSV) causes seasonal epidemics between December and March (April) and remains the main agent that causes severe lower respiratory tract infections in young infants. Children with bronchopulmonary dysplasia up to 24 months of age and preterm infants with a gestational age of 32 weeks and below, who are less than six months of age, are at highest risk for severe RSV infection. RSV-IGIV has been demonstrated to reduce significantly RSV associated hospitalizations, RSV associated hospital days and the incidence of severe RSV lower respiratory tract infections. Monthly infusions during RSV season were safe and well tolerated. Adverse events related to the hyperimmune globulin infusion were generally mild (< 3%) including fluid overload, decreased oxygen saturation and fever. Palivizumab, an intramuscularly administered humanized monoclonal antibody (RSV-glycoprotein-F antibody), will be preferable for the future because of ease of administration and comparable reduction in the risk of hospitalization. RSV-IGIV and palivizumab are both cost expansive and prophylaxis should be limited to high-risk infants.     

Rehospitalization for respiratory syncytial virus infection in infants with extremely low gestational age or birthweight in Denmark

AIM: To determine the risk of rehospitalization for respiratory syncytial virus (RSV) infection during the first 2 y of life in extremely preterm infants. METHODS: Records on all rehospitalizations during the first 2 living years of all infants born with gestational age <28 wk or birthweight <1,000g during 1994 and 1995 in Denmark were retrospectively reviewed. RESULTS: Among 240 eligible infants, 43 (18%) had been rehospitalized 48 times owing to RSV. In infants (n = 210) without CLD the risk of rehospitalization for RSV was 16%, whereas in infants with CLD (n = 30) it was 30% (p = 0.065). Eighteen infants (38%) required respiratory support (supplemental oxygen only 3, continuous positive airway pressure 14, mechanical ventilation 1). Apart from CLD the only factor that could be associated with increased risk of hospitalization for RSV was discharge during autumn (p = 0.05). No infant died from RSV infection. CONCLUSION: The high rate of rehospitalization for RSV in extremely preterm infants in Denmark, especially in infants with CLD, should lead to considerations concerning more widespread use of prophylaxis against RSV in these infants.     

Cost-effectiveness of palivizumab in New Zealand

OBJECTIVE: To establish the preterm infant hospitalization risks from respiratory syncytial virus (RSV) in New Zealand and the net cost per hospitalization averted by palivizumab. METHODS: The 437 infants born < 32 weeks' gestation in 1997 and treated at five major neonatal units were identified. Subsequent admissions during the next 2 years for bronchiolitis, pneumonia and croup were tracked, and information collected on RSV tests performed. Data on the length of stay and hospital costs were used to calculate the potential net cost per hospitalization averted associated with the use of palivizumab and the number needed to treat (NNT) to prevent one hospitalization. RESULTS: Estimated RSV readmission risk before 1 year corrected age in infants < 32 weeks' gestation discharged home on oxygen, and those " 28 weeks' gestation, or between 29 and 31 weeks' gestation with or without chronic lung disease was 42%, 23%, 19%, 10% and 8%, respectively. The NNT with palivizumab to prevent one hospitalization ranged from six to 26 across subgroups. Mean (range) net cost per hospitalization averted was 60,000 New Zealand dollars ($28,000-$166,700). In no subgroup would prophylaxis result in net cost saving. Prophylaxis for all NZ infants " 28 weeks' gestation would cost approximately $1,090,000 net and prevent 29 hospitalizations annually, being equivalent to $37,000 net per hospitalization averted, with eight infants treated to prevent one hospitalization. Alternative assumptions about cost and efficacy failed to alter these findings. CONCLUSION: If value is placed on preventing morbidity, the priority groups for palivizumab prophylaxis are preterm infants discharged home on oxygen, followed by preterm infants of 28 weeks' gestation or less.     

Prevention of respiratory syncytial virus infections in high-risk infantsby monoclonal antibody (palivizumab)

Respiratory syncytial virus (RSV) is a major viral pathogen which causes serious respiratory illness in infants and children worldwide. Palivizumab (Synagis) is an anti-RSV monoclonal antibody administered intramuscularly for the prevention of severe RSV respiratory disease in high-risk infants and young children. The IMpact-RSV trial, the pivotal multicenter, randomized, placebo-controlled trial performed in the USA, Canada and the United Kingdom demonstrated an overall 55% reduction in hospitalization rate due to RSV infection in preterm infants (< or = 35 weeks gestation) with and without chronic lung disease (CLD). Subgroup analysis in premature infants without CLD revealed an even greater reduction in RSV hospitalization rates (78%). Adverse events were infrequent and did not differ between placebo and palivizumab groups. Injection site reactions were infrequent and mild; no differences were observed between palivizumab and placebo subjects. Palivizumab does not interfere with administration of other pediatric vaccines. Comprehensive parent education programs regarding prevention of infection, avoidance of risk factors for infection, careful adherence to infection control policies, and recognition of early symptoms of RSV infection remain important components of RSV prevention strategies. In light of the lack of effective vaccines for this serious health risk, palivizumab offers the only option for prophylaxis against RSV disease in high-risk infants.     

Impact of palivizumab prophylaxis on respiratory syncytial virus hospitalizations in high risk Alaska Native infants

BACKGROUND: Alaska Native children experience extremely high rates of hospitalization for respiratory syncytial virus (RSV) infection. We evaluated the effect of palivizumab prophylaxis on the incidence of RSV hospitalizations in high risk Alaska Native children. METHODS: We analyzed two retrospective cohorts. The first analysis, of southwest Alaska Native children hospitalized with acute respiratory infections during 1993 to 1996 and 1998 to 2001, compared RSV hospitalization rates among premature and nonpremature infants born before (1993 to 1996) and after (1998 to 2001) palivizumab use. The second analysis, of Alaska Native infants with a history of prematurity or lung disease during 1998 through 2001, compared RSV hospitalization among children receiving palivizumab during protected periods (within 32 days after a dose of palivizumab) and unprotected periods. RESULTS: First RSV hospitalizations in premature infants from southwest Alaska meeting criteria for palivizumab prophylaxis decreased from 439 per 1000 births before to 150 per 1000 births after palivizumab (relative rate, 0.34; 95% confidence interval, 0.17 to 0.68), whereas the rate in nonpremature infants remained stable (148 per 1000 births compared with 142 per 1000). Among high risk Alaska Native children during 1998 through 2001, the rate of first RSV hospitalization was 0.55 per 1000 protected days and 1.07 per 1000 unprotected days (relative rate, 0.52; 95% confidence interval, 0.28 to 0.93). CONCLUSIONS: Palivizumab reduced RSV hospitalizations in high risk infants in a region with high rates of RSV hospitalization.     

Prophylaxis of respiratory syncytial virus in Canada in 2003

Passive immunization of high-risk children with the humanized monoclonal antibody palivizumab is the mainstay of respiratory syncytial virus (RSV) prophylaxis in Canada in 2003. This product appears to be safe, and it prevents the majority of RSV hospitalizations in infants born before 36 weeks gestational age, and about half in children under 24 months of age with hemodynamically significant congenital heart disease. However, the high cost of palivizumab and the fact that at least 12 infants need to be treated throughout RSV season to prevent one hospitalization make it difficult to determine the ideal indications for the product. Because these high-risk infants account for a minority of RSV hospitalizations, it is desirable to search for a prophylactic strategy that is practical to apply in all infants.     

Risk Factors for Hospitalization due to Lower Respiratory Tract Infection in Preterm Infants on Palivizumab Prophylaxis

Objective

To determine the risk factors associated with lower respiratory tract infections (LRTI) related hospitalizations in preterm infants receiving palivizumab throughout the high season for respiratory syncytial virus (RSV) infection.

Methods

Premature infants who were commenced on palivizumab prophylaxis during the RSV season were included in the study following parental consent. Information on demographic, social, prenatal and postnatal clinical characteristics was recorded and risk factors associated with hospitalization were evaluated for each patient.

Findings

While 234 participants (Group 1, 92.8%) did not require hospitalization during the study period, 18 patients (Group 2, 7.2%) were hospitalized at least once for LRTI during the RSV season. The rate of moderate-severe bronchopulmonary dysplasia (BPD) was significantly higher in group 2 compared to group 1 (38.9% vs 16.2%; P=0.016). Of the 18 infants who were hospitalized, 6 (33.3%) tested positive for RSV while the remaining 12 patients (66.7%) were negative for RSV. Odds ratio (OR) analysis of several risk factors revealed the presence of BPD (OR: 3.28; 95%CI: 1.19-9), being from a family with low socioeconomic status (OR: 3.64; 95%CI 1.08-12.3) to be associated with a higher likelihood of LRTI-related hospitalization.

Conclusion

Our data demonstrated that RSV is an important LRTI agent and cause of hospitalization especially in preterm infants with additional risks such as BPD, gestational age of <28 weeks and low socioeconomic status. We suggest that improving care conditions and decreased BPD with prematurity would help in prevention of LRTI hospitalization.     

Effectiveness of palivizumab: evaluation of outcomes from the 1998 to 1999 respiratory syncytial virus season. The Palivizumab Outcomes Study Group

BACKGROUND: Respiratory syncytial virus (RSV) remains a significant cause of morbidity, especially in premature infants and immunocompromised children, resulting in approximately 100 000 hospitalizations annually. A study was performed to evaluate the outcomes of those given palivizumab (Synagis; MedImmune, Inc., Gaithersburg, MD) during the 1998 to 1999 RSV season, its first season in general use. METHODS: A retrospective chart review of 1839 patients from 9 United States sites was conducted, representing all patients given palivizumab at each site. Those evaluated were to have a gestational age of < or =35 weeks, were to be <2 years old at their first injection and were to have received at least one dose of palivizumab (humanized monoclonal antibody against RSV) between September, 1998, and May, 1999. Gestational age, comorbidities, frequency of injections, hospitalizations and length of hospital stays were assessed. RESULTS: The antigen- or culture-positive RSV hospitalization rates for those given prophylaxis were 2.3% (42 of 1839) overall, 16/399 (4.0%) with chronic lung disease of infancy and 26 of 1227 (2.1%) born prematurely without chronic lung disease of infancy. Twenty-six patients had a gestational age of >35 weeks and were included in the analysis. CONCLUSIONS: Only 2.3% of children receiving palivizumab prophylaxis were hospitalized with RSV lower respiratory infection. This compares favorably with the rates observed in the pivotal trial (IMpact-RSV trial in 1996 to 1997), in which prophylaxis reduced hospitalization from 10.6% in the placebo group to 4.8% in those children receiving prophylaxis.     

Respiratory syncytial virus and premature infants born at 32 weeks' gestation or earlier: hospitalization and economic implications of prophylaxis

OBJECTIVES: To assess the risk of hospitalization associated with respiratory syncytial virus (RSV) and to estimate the economic impact of RSV prophylaxis with either RSV immune globulin (RSV-Ig) or RSV monoclonal antibody (palivizumab) on a cohort of preterm infants born at 32 weeks' gestation or earlier. DESIGN: Historical cohort study. SETTING: A 12-county neonatal network served by the regional center in Rochester, NY. PARTICIPANTS: One thousand twenty-nine infants born at 32 weeks' gestation or earlier followed up until 1 year of corrected age. MAIN OUTCOME MEASURES: Rate of hospitalization with an RSV-associated illness; cost per hospitalization prevented resulting from either form of RSV prophylaxis. RESULTS: The probability of hospitalization with an RSV-associated illness for infants born at 32 weeks' gestation or earlier was estimated at 11.2%. The incidence of RSV hospitalization increased with decreasing gestational age (13.9% vs 4.4% for infants born at < or =26 weeks' gestation vs those born at 30-32 weeks' gestation). Infants requiring respiratory support at 36 weeks of postconceptual age (PCA) or older had a higher hospitalization rate (16.8% vs 6.2%), longer hospital stays, and higher hospital charges than infants requiring respiratory support at less than 36 weeks of PCA. For infants requiring respiratory support at less than 36 weeks of PCA, the incidence of RSV hospitalization still increased with decreasing gestational age (10.2% vs 4.3% for infants < or =26 weeks' gestation vs those 30-32 weeks' gestation). Analysis indicated that both forms of RSV prophylaxis would increase the net cost of care for all groups. Palivizumab was more cost-effective than RSV-Ig for preventing RSV hospitalization among infants who required respiratory support at less than 36 weeks of PCA, especially those born at 26 weeks' gestation or earlier. Overall, RSV-Ig was more cost-effective than palivizumab for infants requiring respiratory support at 36 weeks of PCA or older. CONCLUSIONS: This analysis suggests that available forms of RSV prophylaxis would increase the net cost of care not only for the entire cohort but for each of the subgroups studied. However, the RSV hospitalization rate and the cost-effectiveness of prophylaxis varied markedly by subgroup.     

Are late preterm infants as susceptible to RSV infection as full term infants?

Preterm infants are at increased risk of being rehospitalised during the first few months of life with severe respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) that usually manifests as apnea and hypoxemia. This occurs more commonly in preterm infants < 33 weeks gestational age (GA), but recent studies demonstrate that late preterm infants (those born between 34 weeks and 0 days to 36 weeks and 6 days GA) are equally susceptible to RSV LRTI as those with lower GA. Factors associated with severe LRTI include immaturity of both the humoral and cell-mediated immune system and interrupted lung development prior to 36 weeks GA which results in lower functional residual capacity, reduced compliance, diminished forced expiratory air flow and impaired gas exchange. Morbidity and mortality are significantly increased in late preterms compared to their term counterparts. Prophylaxis with palivizumab against RSV infection seems to be crucial. Due to the large number of infants in this age group, additional risk factors have been identified in order to tailor palivizumab prophylaxis effectively to those at highest risk for severe RSV LRTI.     

Net cost of palivizumab for respiratory syncytial virus prophylaxis during the 1998/99 season in northern Alberta

OBJECTIVE:

Palivizumab has been shown to decrease respiratory syncytial virus (RSV) hospitalization rates in preterm infants and infants with chronic lung disease. The objective of the present study was to determine whether the use of palivizumab during the 1998/99 RSV season would have resulted in a cost-saving in infants discharged from Edmonton hospitals.

DESIGN:

A retrospective study of RSV hospitalizations was performed by contacting parents and reviewing hospital lists. The net cost of using palivizumab was determined by comparing the cost of giving the drug from November 1, 1998 to April 1, 1999 with the cost of potentially averted medical transports and hospitalizations.

POPULATION:

One hundred fifty-nine infants discharged from Edmonton hospitals who met the Canadian Paediatric Society’s criteria for receiving palivizumab during the 1998/99 RSV season were studied.

RESULTS:

The cost of using palivizumab in these 159 study infants would have been $753,300. The infants had 21 RSV hospitalizations and required four medical transports. The estimated cost of RSV hospital-based care for these infants was $168,888. Assuming a drug efficacy of 39% in infants with chronic lung disease and 78% in infants born before 33 weeks’ gestation with no chronic lung disease, $121,147 of these costs could have been averted if palivizumab had been used.

CONCLUSIONS:

The net cost to the health care system of using palivizumab, as recommended in the Canadian Paediatric Society guidelines, in study infants in northern Alberta during the 1998/99 RSV season would have been $632,153.     

Recommendations for the prevention of respiratory syncytial virus infections. Standards Committee of the Spanish Society of Neonatology. Board of Directors of the Spanish Society of Neonatology

Premature babies < = 35 weeks gestation, with or without chronic lung disease (CLD), should be considered high risk population for RSV infection and rehospitalization. RSV monoclonal antibodies (palivizumab) have been found useful in decreasing rates of RSV hospitalization in this patients. Guidelines for their administration include: 1. Recommend their use in premature born between 29-32 weeks gestation without CLD and less than 6 months at entry of RSV station. 2. Strongly recommend their use in premature babies < = 28 weeks gestation or affected with CLD in treatment during last 6 months. These patients should be prophylaxed for two RSV seasons. 3. Prophylaxis among premature babies between 32-35 weeks gestation is not recommended on routine bases. Each case has to be individually analyzed considering risk factors.     

Prenatal predictors of chronic lung disease in very preterm infants

OBJECTIVE: To identify prenatal risk factors for chronic lung disease (CLD) at 36 weeks postmenstrual age in very preterm infants. POPULATION: Data were collected prospectively as part of the ongoing audit of the Australian and New Zealand Neonatal Network (ANZNN) of all infants born at less than 32 weeks gestation admitted to all tertiary neonatal intensive care units in Australia and New Zealand. METHODS: Prenatal factors up to 1 minute of age were examined in the subset of infants born at gestational ages 22-31 weeks during 1998-2001, and who survived to 36 weeks postmenstrual age (n = 11 453). Factors that were significantly associated with CLD at 36 weeks were entered into a multivariate logistic regression model. RESULTS: After adjustment, low gestational age was the dominant risk factor, with an approximate doubling of the odds with each week of decreasing gestational age from 31 to less than 25 weeks (trend p<0.0001). Birth weight for gestational age also had a dose-response effect: the lower the birth weight for gestational age, the greater the risk, with infants below the third centile having 5.67 times greater odds of CLD than those between the 25th and 75th centile (trend p<0.0001). There was also a significantly increased risk for male infants (odds ratio 1.51 (95% confidence interval 1.36 to 1.68), p<0.0001). CONCLUSIONS: These population based data show that the prenatal factors low gestational age, low birth weight for gestational age, and male sex significantly predict the development of chronic respiratory insufficiency in very preterm infants and may assist clinical decision about delivery.     

Severe respiratory syncytial virus bronchiolitis: epidemiologic variations associated with the initiation of palivizumab in severely premature infants with bronchopulmonary dysplasia

BACKGROUND: The efficacy of palivizumab prophylaxis after bronchopulmonary dysplasia (BPD) has been demonstrated in a single placebo-controlled trial. Concern has emerged about the degree of efficacy of palivizumab.This study was designed to determine the efficacy of administration of palivizumab to premature infants with a gestational age 相似文献   

Incidence and risk factors of respiratory syncytial virus-related hospitalizations in premature infants in Germany

Premature infants have an increased risk of developing complicated respiratory syncytial virus (RSV) infections. Epidemiological data on RSV-related hospitalizations are a prerequisite to develop guidelines for the use of preventive measures. The objective of this study was to determine incidence and risk factors of RSV-related rehospitalizations (RSV-RH) of premature infants. We recruited 1,103 infants with a gestational age of less than 35 weeks, primarily admitted to nine neonatologic care units in southern Germany between Nov. 1, 1998 and Oct. 31, 1999. Questionnaires were sent to all parents of infants discharged from neonatal care units to determine the risk of rehospitalization for acute respiratory infections (ARI-RH) and RSV-RH in the 1999-2000 season. The questionnaire response rate was 68.4%. The 717 included infants of the responders had a mean gestational age of 31.6 weeks (Range: 23-35) and a mean birth weight of 1,747 g (range: 430-4,050 g). The risk for an ARI-RH was 10.6% and the risk for RSV-RH 5.2% during the observation period. Premature infants with chronic lung disease (CLD) had a probability of 24.5% for ARI-RH and of 15% for RSV-RH. The following factors were independently associated with an increased risk of RSV-RH: male gender (adjusted Odds-Ratio (OR): 8.7; 95% confidence interval (CI): 2.6-29.1), chronic lung disease (OR: 3.99; 95%CI: 1.4-11.2), discharge between October and December (OR: 2.1; 95%CI: 0.99-4.4), day-care attendance of siblings (OR: 3.9; 95%CI: 1.9-8.3). Conclusions: The risk for RSV rehospitalization among premature infants discharged from neonatal care facilities in southern Germany was low. Additional risk factors and high costs of prophylaxis have to be considered when infants are selected for RSV prophylaxis using monoclonal antibodies.     

Eligibility for palivizumab prophylaxis in a cohort of children with severe bronchiolitis

In 2014, the American Academy of Pediatrics (AAP) updated their recommendations for palivizumab prophylaxis for children who are at high risk for severe respiratory syncytial virus (RSV) infection. To investigate the potential impact of the more restrictive 2014 criteria on the eligibility for palivizumab prophylaxis, we applied the 2012 and 2014 AAP recommendations for palivizumab prophylaxis to a multicenter cohort of 2207 US children hospitalized for bronchiolitis. According to the 2012 AAP recommendations, 215 children (9.7%) were eligible for palivizumab prophylaxis, while 140 children (6.3%) would have been eligible based on the 2014 updated recommendations (34.9% relative decrease; 95%CI: 28.5–41.7%). The decrease was largely driven by the restriction of eligibility to preterm infants with gestational age <29 weeks. Further development of and refinement of cost‐effective approaches for the prevention of severe RSV infection are needed.     

Hospitalization rates for respiratory syncytial virus infection in premature infants born during two consecutive seasons.

OBJECTIVE: To collect data on hospitalization rates for respiratory syncytial virus (RSV) illness during the season of 1999 to 2000 in nonprophylaxed premature infants < or = 32 weeks gestational age (GA) in Spain and compare this with previously published data collected in the season of 1998 to 1999. METHODS: Children born at < or = 32 weeks GA between April 1, 1999, and April 31, 2000, and discharged from the hospital before April 31, 2000, were included. Neonatal and demographic data were obtained at the initial visit. Study subjects were followed at monthly intervals throughout the respiratory season. RSV status and morbidity data were collected on patients rehospitalized for respiratory illness. RESULTS: The 999 evaluable patients in the 2000 season were comparable to the 1999 sample, except for higher rates of family allergy history and number of multiple deliveries and a lower rate of neonatal morbidity. The hospitalization rate for RSV illness was 13.4% in the 1999 season and 13.1% in the 2000 season; 10 (8%) were RSV reinfections in the 2000 season. Significant independent prognostic variables for high risk of RSV hospital admission included: lower gestational age; chronologic age < 3 months at onset of the RSV season; living with school age siblings; and exposure to tobacco smoke. CONCLUSIONS: Hospitalization rates for RSV disease in nonprophylaxed preterm infants < or = 32 weeks GA were high in Spain and comparable during two consecutive RSV seasons (13%). Readmission for a second RSV infection was also common.