Evaluation of the safety of palivizumab in the second season of exposure in young children at risk for severe respiratory syncytial virus infection

Home Immunization with Palivizumab-A Randomized Pilot Study Describing Safety Aspects and Parents' Preferences

Among prematurely born infants and newborns with chronic conditions, a respiratory syncytial virus (RSV) infection may cause (re-)admission and later respiratory complications. Therapeutic protection is possible with monthly injections of a specific monoclonal antibody, palivizumab, during RSV season. Standard care is giving up to five injections in clinic-based settings. Immunization at home could be an alternative to standard care for vulnerable infants to reduce the number of revisits and associated risk of RSV infection. The aim of this randomized pilot trial was to evaluate safety aspects and explore parents' preferences of home versus hospital immunization with palivizumab during one RSV season. Immediate adverse events (AEs) were observed and registered by a pediatric specialist nurse. Late-onset AEs were reported by parents. Parents' perceptions were collected through a questionnaire and analyzed using content analysis. The study population consisted of 43 infants in 38 families. No immediate AEs occurred. Three late-onset AEs were reported in two infants in the intervention group. Three categories emerged in the content analysis: (1) protect and watch over the infant, (2) optimal health and well-being for the whole family, and (3) avoid suffering for the infant. The study results show that home immunization with palivizumab is feasible if safety aspects are considered and that parental involvement in the choice of place for immunization after a neonatal intensive care experience can be important.

Antibody development for preventing the human respiratory syncytial virus pathology

Human respiratory syncytial virus (hRSV) is the most important etiological agent causing hospitalizations associated with respiratory diseases in children under 5 years of age as well as the elderly, newborns and premature children are the most affected populations. This viral infection can be associated with various symptoms, such as fever, coughing, wheezing, and even pneumonia and bronchiolitis. Due to its severe symptoms, the need for mechanical ventilation is not uncommon in clinical practice. Additionally, alterations in the central nervous system -such as seizures, encephalopathy and encephalitis- have been associated with cases of hRSV-infections. Furthermore, the absence of effective vaccines or therapies against hRSV leads to elevated expenditures by the public health system and increased mortality rates for the high-risk population. Along these lines, vaccines and therapies can elicit different responses to this virus. While hRSV vaccine candidates seek to promote an active immune response associated with the achievement of immunological memory, other therapies -such as the administration of antibodies- provide a protective environment, although they do not trigger the activation of the immune system and therefore do not promote an immunological memory. An interesting approach to vaccination is the use of virus-neutralizing antibodies, which inhibit the entry of the pathogen into the host cells, therefore impairing the capacity of the virus to replicate. Currently, the most common molecule targeted for antibody design against hRSV is the F protein of this virus. However, other molecular components of the virus -such as the G or the N hRSV proteins- have also been explored as potential targets for the control of this disease. Currently, palivizumab is the only monoclonal antibody approved for human use. However, studies in humans have shown a protective effect only after the administration of at least 3 to 5 doses, due to the stability of this vaccine. Furthermore, other studies suggest that palivizumab only has an effectiveness close to 50% in high-risk infants. In this work, we will review different strategies addressed for the use of antibodies in a prophylactic or therapeutic context and their ability to prevent the symptoms caused by hRSV infection of the airways, as well as in other tissues such as the CNS.

Risk Factors and Main Indications for Palivizumab Prophylaxis in a Second Season Population: Results From the German Synagis Registry 2009-2016

BACKGROUND

After national recommendations, palivizumab is administered in Germany to high-risk infants to prevent hospitalizations related to respiratory syncytial virus (RSV) infection. Limited data are available to characterize those children who receive palivizumab in 2 consecutive RSV seasons.

METHODS

This was a comparative analysis of data from a postmarketing observational study (German SYNAGIS Registry, AbbVie Germany GmbH & Co.KG, Wiesbaden) detailing RSV-related risk factors and main indications for palivizumab in 920 children who received at ≥1 palivizumab injection in a second season between 2010 and 2016 [second season population (SSP)].

RESULTS

Median birth weight and gestational age at birth as well as the proportion of children with hemodynamically significant congenital heart disease, with any form of chronic lung disease of prematurity or with any form of neuromuscular impairment, were significantly higher in the SSP. Accordingly, hemodynamically significant congenital heart disease, chronic lung disease and other reasons (including neuromuscular impairment) and not prematurity were the main indications for palivizumab in the SSP. The RSV-related hospitalization rate confirmed by viral testing in the SSP (receiving palivizumab prophylaxis) was 0.9%. No deaths due to RSV were reported.

CONCLUSIONS

Second season recipients of palivizumab differ from one season recipients of palivizumab in terms of risk factors and main indications for prophylaxis. Keeping in mind the limitations of an uncontrolled prospective observational study, these results support the effectiveness of palivizumab (concerning the RSV rehospitalization rate) and do not reveal new safety alerts in a large SSP.

Palivizumab Prophylaxis Against Respiratory Syncytial Virus Infection in Children with Immunocompromised Conditions or Down Syndrome: A Multicenter, Post-Marketing Surveillance in Japan

OBJECTIVE

The aim of this study was to assess the safety and effectiveness of palivizumab for the prevention of lower respiratory tract infection (LRI) caused by respiratory syncytial virus (RSV) in children with immunocompromised conditions or Down syndrome.

METHODS

In this multicenter, post-marketing surveillance study (December 2013 to December 2015), children aged ≤24 months with immunocompromised conditions or Down syndrome (without hemodynamically significant congenital heart disease) receiving palivizumab immunoprophylaxis during two RSV seasons were observed until 30 days after the final palivizumab injection. Safety [adverse events (AEs), serious AEs (SAEs), adverse drug reactions (ADRs), serious ADRs (SADRs)] and effectiveness (frequency, incidence, and duration of hospitalization due to RSV infections) were assessed.

RESULTS

Of 304 patients receiving palivizumab, 167 (54.9%) had immunocompromised conditions, and 138 (45.4%) had Down syndrome; 260 (85.5%) completed palivizumab immunoprophylaxis. The annual mean (±standard deviation) number of doses was 5.3 (±2.4) per season. Overall, 220 AEs occurred in 99 patients (32.6%), including 89 SAEs in 53 patients (17.4%). Of these, 33 AEs in 25 patients (8.22%) were considered ADRs, and 13 ADRs in 11 patients (3.62%) were considered SADRs. In four patients, five SADRs (nephroblastoma and asthma in the same patient, septic shock, device-related infection, and drug-induced liver injury) were previously unreported; however, none were considered drug-related. During the observation period, five RSV infections occurred and two patients required hospitalization.

CONCLUSION

Palivizumab was generally safe and effective for the prevention of LRI caused by RSV in newborns, infants, and children with immunocompromised conditions or Down syndrome up to the age of 24 months.

Product review on the monoclonal antibody palivizumab for prevention of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) accounts for about 20% of all respiratory infections in children below the age of 5 y. It is associated with up to 63% of all acute respiratory infections and up to 81% of all viral lower respiratory tract infections causing hospitalization in infants and young children. RSV leads to seasonal epidemics between November and April in the northern hemisphere. Most severe infections (RSV accounts for 50 to 80% of all cause bronchiolitis) affect infants younger than 6 months of age and high-risk infants including those born preterm with or without bronchopulmonary dysplasia and those with hemodynamically significant congenital heart disease up to an age of 24 months. Palivizumab, a highly potent RSV-neutralizing monoclonal antibody (Mab), has been licensed in 1998 for prophylactic use to prevent RSV associated hospitalizations in high-risk infants. This Mab is given by monthly intramuscular injection at a dose of 15 mg/kg over the RSV season (up to 5 times). Palivizumab proved to be safe and well-tolerated in this population. Concerns have been raised regarding cost-effectiveness of palivizumab and thus, palivizumab prophylaxis is mainly limited to selected high-risk infants for the first RSV season. Long-lasting Mabs will be the next future approach in the prophylaxis of RSV hospitalization until a vaccine is developed.

Serious Adverse Events in the Canadian Registry of Children Receiving Palivizumab (CARESS) for Respiratory Syncytial Virus Prevention

OBJECTIVES

To evaluate the safety and tolerability of palivizumab for RSV prophylaxis in high-risk children in everyday practice.

METHODS

High-risk children prophylaxed against RSV infection were recruited into a prospective, observational, Canadian RSV Evaluation Study of Palivizumab (CARESS) registry with active, serious adverse event (SAE) monitoring from 2008 to 2013. SAE reports were systematically collected and assessed for severity and relationship to palivizumab. Data were analyzed by Chi-square or Fisher Exact Tests to examine group differences in proportions.

RESULTS

13025 infants received 57392 injections. Hospitalizations for respiratory-related illness (RIH) were reported in 915 patients, and SAEs other than RIH were reported in 52 patients. Of these, 6 (0.05%) patients had a total of 14 hypersensitivity reactions that were deemed possibly or probably related to palivizumab (incidence: 2.8 per 10,000 patient-months). The SAEs of 42 patients were assessed as not related to palivizumab. SAEs in the remaining 4 patients were not classifiable as their records were incomplete. There were no significant demographic predictors of SAE occurrence.

CONCLUSIONS

Under active surveillance, a small proportion of infants in the CARESS registry experienced SAEs that had a potential relationship with palivizumab and these appeared to be unpredictable in terms of onset. Palivizumab appears to be a safe and well-tolerated antibody for RSV prophylaxis in high-risk children in routine practice.

Safety and Effectiveness of Palivizumab in Children at High Risk of Serious Disease Due to Respiratory Syncytial Virus Infection: A Systematic Review

INTRODUCTION

Lower respiratory tract infection (LRTI) is the leading cause of infant mortality globally in post-neonatal infants (i.e., 28-364 days of age). Respiratory syncytial virus (RSV) is the most commonly identified pathogen for infant LRTI and is the second most important cause of death in post-neonatal infants. Despite 50 years of RSV vaccine research, there is still no approved vaccine. Therefore, passive immunity with the monoclonal antibody palivizumab is the sole regulatory-approved option for the prevention of serious LRTI caused by RSV in pediatric patients at high risk of RSV disease.

METHODS

We conducted a comprehensive systematic literature review of randomized controlled trials (RCTs), open-label non-comparative clinical trials, and prospective observational studies/registries, and summarized the evidence related to the safety, efficacy, and effectiveness of palivizumab.

RESULTS

The efficacy of palivizumab, as measured by the relative reduction in RSV-related hospitalization rate compared with placebo ranged from 39% to 78% (P < 0.05) in the 2 pivotal RCTs. A meta-analysis of the RSV-related hospitalization rate from 5 randomized placebo-controlled trials yielded an overall odds ratio of 0.41 (95% CI, 0.31-0.55) in favor of palivizumab prophylaxis over placebo (P < 0.00001). Low rates of RSV-related hospitalizations were observed in palivizumab recipients consistently over time in more than 42,000 pediatric subjects across 7 RCTs, 4 open-label non-comparative trials, and 8 observational studies/registries conducted in 34 countries. In addition, among palivizumab-prophylaxed subjects with breakthrough RSV LRTI, rates of intensive care unit admission and mechanical ventilation from RSV hospitalization also were low and consistent across studies. With respect to safety, no differences were observed between palivizumab and placebo in the blinded RCTs.

CONCLUSION

Rates of RSV hospitalizations and RSV hospitalization-related endpoints in pediatric subjects who received prophylaxis with palivizumab were low and constant over time and across RCTs, open-label non-comparative trials, and observational studies/registries.

Updated guidance for palivizumab prophylaxis among infants and young children at increased risk of hospitalization for respiratory syncytial virus infection

Guidance from the American Academy of Pediatrics (AAP) for the use of palivizumab prophylaxis against respiratory syncytial virus (RSV) was first published in a policy statement in 1998. Guidance initially was based on the result from a single randomized, placebo-controlled clinical trial conducted in 1996-1997 describing an overall reduction in RSV hospitalization rate from 10.6% among placebo recipients to 4.8% among children who received prophylaxis. The results of a second randomized, placebo-controlled trial of children with hemodynamically significant heart disease were published in 2003 and revealed a reduction in RSV hospitalization rate from 9.7% in control subjects to 5.3% among prophylaxis recipients. Because no additional controlled trials regarding efficacy were published, AAP guidance has been updated periodically to reflect the most recent literature regarding children at greatest risk of severe disease. Since the last update in 2012, new data have become available regarding the seasonality of RSV circulation, palivizumab pharmacokinetics, the changing incidence of bronchiolitis hospitalizations, the effects of gestational age and other risk factors on RSV hospitalization rates, the mortality of children hospitalized with RSV infection, and the effect of prophylaxis on wheezing and palivizumab-resistant RSV isolates. These data enable further refinement of AAP guidance to most clearly focus on those children at greatest risk.

Cost-effectiveness of palivizumab in infancy

Respiratory syncytial virus is the most common cause of bronchiolitis, a lower respiratory tract infection occurring in infancy. It is responsible for several rehospitalizations, substantial morbidity and occasional deaths in the UK every year. Palivizumab is a recombinant monoclonal antibody that has been shown to reduce hospitalizations in infected infants. It is licensed for high-risk infants, primarily those born pre-term or with chronic pulmonary or cardiac conditions. Palivizumab is expensive, but several economic analyses have determined highly discrepant costs. This article reviews the limitations of the available efficacy and economic data, and highlights problems in interpretation and extrapolation. We also present the results of a cost-effectiveness analysis relevant to populations of high-risk infants in the UK.

Respiratory syncytial virus prevention in children with congenital heart disease: who and how?

Respiratory syncytial virus (RSV) is a major cause of respiratory infection in children. Most of the pediatric population have RSV infection before the age of 2, and recurrent infections are common even within one season. Chronic lung disease, prematurity, along with congenital heart disease (CHD) are major risk factors in severe lower respiratory infection. In hemo-dynamically significant CHD patients with RSV infection, hospitalization is usually needed and the possibility of treatment in intensive care unit and the use of mechanical ventilator support are known to increase. Therefore the prevention of RSV infection in CHD patients is mandatory. The current standard for RSV prevention is immunoprophylaxis by palivizumab. Immunoprophylaxis is recommended monthly in hemodynamically significant CHD patients, up to 5 months. Motabizumab, a second generation drug and newly developing RSV vaccines are also expected to play a key role in RSV prevention in the future. The prophylaxis of RSV infection in CHD patients is cost-effective in both the medical aspect of the patients as well as the socio-economic aspect. Therefore an effort to promote prevention should be made by not only the family of the patients but also by the government.

Respiratory syncytial virus prevention and therapy: past, present, and future

Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children worldwide. More than 50 years after its discovery, and despite relentless attempts to identify pharmacological therapies to improve the clinical course and outcomes of this disease, the most effective therapy remains supportive care. Although the quest for a safe and effective vaccine remains unsuccessful, pediatricians practicing during the past decade have been able to protect at least the more vulnerable patients with safe and effective passive prophylaxis. This review summarizes the history, microbiology, epidemiology, pathophysiology, and clinical manifestations of this infection in order to provide the reader with the background information necessary to fully appreciate the many challenges presented by the clinical management of young children with bronchiolitis. The last part of this article attempts an evidence-based review of the pharmacologic strategies currently available and those being evaluated, intentionally omitting highly experimental approaches not yet tested in clinical trials and, therefore, not likely to become available in the foreseeable future.

[Consensus conference on acute bronchiolitis (v): prevention of acute bronchiolitis. Review of scientific evidence]

A review of the evidence on prevention of acute bronchiolitis is presented. Acute bronchiolitis prevention arises from three basic approaches: preventive treatment to reduce recurrent wheezing following an episode of acute bronchiolitis, preventive treatment to reduce the frequency and severity of RSV bronchiolitis in the population at risk (prematurity, bronchopulmonary dysplasia, congenital heart disease, etc.), and general preventive measures to reduce nosocomial infection with RSV. There is sufficient evidence on the lack of efficacy of inhaled corticosteroids, oral corticosteroids and montelukast. Intravenous RSV immunoglobulin has an unfavorable risk-benefit balance, particularly with the availability of monoclonal antibodies. Palivizumab is effective as preventive treatment of RSV infection in risk populations (high risk preterm infants and hemodynamically significant congenital heart disease), but not in the frequency and severity (ICU admission, need for mechanical ventilation and mortality) of the acute bronchiolitis. The benefits of palivizumab (less admissions) seem to be worth the adverse effects, but we do not know the cost-benefit ratio. The control and prevention measures of nosocomial transmission of RSV infection (isolation, hand washing, use of mask, gloves, cap and shoes) are based on indirect evidence.

Prevention of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract infection in young children, with significant numbers of premature infants and those with other risk factors requiring hospitalization in Canada each year. Palivizumab, an RSV-specific monoclonal antibody, can reduce the hospitalization rate and severity of illness for a small group of high-risk or premature infants during their first RSV season. The present statement reviews the published literature and provides recommendations regarding its use in premature and other at-risk infants, for Canadian physicians.

Clinical relevance of prevention of respiratory syncytial virus lower respiratory tract infection in preterm infants born between 33 and 35 weeks gestational age

Premature infants are vulnerable to severe respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) resulting in hospitalisation and the potential for longer-term respiratory morbidity. Whilst the severity and consequence of RSV LRTI are generally accepted and recognised in infants born <or=32 weeks gestational age (GA), there is less acknowledgment of the potential consequences in infants born 33-35 weeks GA. However, there is a growing body of evidence suggesting that infants born between 33 and 35 weeks GA may be equally at risk for RSV LRTI as infants born <32 weeks GA. Interrupted lung development and an immature immune system have been linked with an increased susceptibility for RSV LRTI, along with other environmental, social, and physiological risk factors. Currently, the only effective method of preventing RSV LRTI is prophylaxis with palivizumab. Often with limited healthcare resources, identifying infants at greatest risk of RSV LRTI who would potentially benefit most from prophylaxis is highly desirable, particularly in the 33-35-week GA group. The purpose of this article is to examine the causes and consequences of RSV LRTI in infants born 33-35 weeks GA, and look at the potential for using risk factors to identify high risk infants and, thereby, optimise prophylaxis. The causes and consequences of RSV LRTI in infants born 33-35 weeks GAA were determined via literature review. A number of underlying risk factors that significantly increase the risk of severe RSV LRTI and subsequent hospitalisation in this group of infants have been identified, most notably from the FLIP and PICNIC studies. A European predictive model based on the risk factors in the FLIP study has recently been developed and validated, which will aid identification of infants born between 33 and 35 weeks GA with the highest risk of RSV hospitalisation. Implementation of this model and prophylaxis of infants born between 33 and 35 weeks GA should be a national or regional decision, taken in perspective of other public health needs.

[Recommendations for the prevention of respiratory syncytial virus infection]

Premature babies < or = 35 weeks gestation, with or without chronic lung disease (CLD), and infants affected by severe congenital heart disease should be considered high risk population for RSV infection and hospitalization. Hygienic measures and RSV monoclonal antibodies (palivizumab) have been found useful in decreasing rates of RSV hospitalization in these patients. Guidelines for their administration include: a) strongly recommended use in premature babies < or = 28 weeks gestation, or born between 29-32 weeks gestation and less than 6 months at start of RSV station or discharged along it, or affected by CLD in treatment during last 6 months or by severe congenital heart disease. Last two groups could be prophylaxed for two RSV seasons. b) Recommended use among premature babies between 32-35 weeks gestation and less than 6 months of age and presenting two or more risk factors: chronologic age < 10 weeks at start of RSV station, breastfeeding < or = 2 months (physician prescription), sibling < 14 years old, day-care assistance, family history of wheezing, > or = 4 adults at home, airways malformation or neuromuscular disease.

Safety and immunogenicity of palivizumab (Synagis) administered for two seasons

To evaluate the safety and immunogenicity of palivizumab, 55 children who received palivizumab in the IMpact-RSV trial received 5 monthly doses of 15 mg/kg palivizumab (Synagis) during the subsequent year. The single child with an antipalivizumab titer of >1/40 had no associated serious adverse events and had expected serum palivizumab trough concentrations. Second year palivizumab prophylaxis was safe and well-tolerated.

Effect of double antigen bridging immunoassay format on antigen coating concentration dependence and implications for designing immunogenicity assays for monoclonal antibodies

The double antigen bridging immunoassay has been used extensively for detection of immunogenicity responses to therapeutic monoclonal antibodies. We have analyzed parameters affecting performance of this type of immunoassay including microtiter plate antigen coating concentration, enzyme-labeled antigen conjugate dilution and assay format (one-step versus two-step). We present results demonstrating that the format of the assay has a significant impact on the optimal parameters to maximize assay performance. A one-step assay format achieves maximal sensitivity across a broad range of coating concentrations and at a lower concentration of conjugate than that in a two-step format. In contrast, a two-step format requires very low coating concentrations and higher conjugate concentrations to achieve maximal sensitivity and suffers from significantly reduced sensitivity at higher coating concentrations. Together, these findings indicate that a one-step assay format can greatly reduce the effect of coating concentration variation on assay performance.

Palivizumab for preterm infants. Is it worth it?

Respiratory syncytial virus infection is an important cause of morbidity. Although palivizumab prophylaxis is widely used, it is uncertain whether the cost is justified. A systematic review was therefore performed of the safety, efficacy, and the likely cost effectiveness of prophylaxis for preterm infants in the United Kingdom using a standard search strategy. The only randomised controlled trial identified showed a reduction in hospital admission but no benefit on more serious outcomes. None of the United Kingdom cost studies showed economic benefit for palivizumab prophylaxis. New treatments are rarely cost effective, and, in the absence of a comprehensive economic assessment, continued use for high risk infants may appear justified.

Palivizumab: a review of its use as prophylaxis for serious respiratory syncytial virus infection

Palivizumab (Synagi) is a humanized monoclonal antibody that provides immunoprophylaxis against serious lower respiratory tract infections (LRTIs) caused by respiratory syncytial virus (RSV). RSV is the leading cause of hospitalization for LRTIs in infants, causing winter- or wet-season epidemics. In two double-blind, placebo-controlled trials, intramuscular palivizumab 15 mg/kg every 30 days for 5 months significantly reduced RSV-related hospitalizations by 55% in 1502 infants with prematurity and/or bronchopulmonary dysplasia/chronic lung disease (BPD/CLD) and by 45% in 1287 infants with hemodynamically significant congenital heart disease (HSCHD). Reductions were statistically significant versus placebo in infants with BPD/CLD, with all degrees of prematurity, and with acyanotic/other heart disease. Palivizumab was generally well tolerated, with < or =1.9% of recipients discontinuing treatment for tolerability reasons. In placebo-controlled trials, the most common potentially drug-related adverse events were fever, nervousness, injection-site reactions, and diarrhea. Drug-related events occurred in 7.2-11% of palivizumab recipients in controlled trials (vs 6.9-10% with placebo) and 0-7.9% in open-label trials. Very few serious potentially drug-related adverse events occurred in clinical trials; four occurred in 2 of 285 patients in one open-label trial. No significant anti-palivizumab antibodies developed during palivizumab use. Palivizumab trough serum concentrations were below the recommended 40 microg/mL in about 33% and up to 14% of children prior to their second and third palivizumab injections. In pharmacoeconomic studies, the cost of palivizumab per hospitalization averted was generally lowest in the highest-risk infants. Drug cost was generally the most influential factor in sensitivity analyses. In conclusion, prophylaxis with palivizumab significantly reduces the incidence of RSV-related hospitalization relative to placebo and is generally well tolerated in high-risk infants aged <2 years, including those with prematurity and BPD/CLD or HSCHD, which are risk factors for early or serious RSV infection. Palivizumab is approved for use in these patients. Other high-risk infants in whom palivizumab has not been formally assessed, such as those with immunodeficiency, cystic fibrosis, or location-specific risk factors (including extended hospital stays) might potentially benefit from palivizumab. The use of palivizumab in these other high-risk populations is likely to be determined as much by pharmacoeconomic considerations as by efficacy outcomes.

Demystified...recombinant antibodies

Recombinant antibodies are important tools for biomedical research and are increasingly being used as clinical diagnostic/therapeutic reagents. In this article, a background to humanized antibodies is given, together with details of the generation of antibody fragments--for example, single chain Fv fragments. Phage antibody fragments are fast becoming popular and can be generated by simple established methods of affinity enrichment from libraries derived from immune cells. Phage display methodology can also be used for the affinity enrichment of existing antibody fragments to provide a reagent with a higher affinity. Here, phage antibodies are demystified to provide a greater understanding of the potential of these reagents and to engage clinicians and biomedical scientists alike to think about potential applications in pathology and clinical settings.

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.

Morbidity and mortality after RSV-associated hospitalizations among premature Canadian infants

OBJECTIVE

To evaluate the impact of respiratory syncytial virus (RSV) infections on subsequent health care resource utilization in preterm infants.

STUDY DESIGN

Analysis of data from 2415 preterm infants (32 to 35 weeks gestational age [GA]) hospitalized for proven or probable RSV and matched to 20,254 control infants.

RESULTS

Mean (SD) age at the index admission was 7.7 (5.5) months; 46% of the infants were male. Mean (SD) subsequent health services, excluding the index event, for the RSV cohort and control infants, respectively, were hospitalization, 2.96 (2.81) versus 1.28 (1.42); special care unit visits, 0.67 (1.70) versus 0.40 (0.33); respiratory therapy visits, 0:31 (0.70) versus 0.13 (0.37); physician consults, 3.61 (4.54) versus 0.89 (1.12); in-hospital procedures, 1.05 (4.02) versus 0.81 (1.51); outpatient visits, 18.4 (10.58) versus 7.54 (4.31); and mean (SD) inpatient days, 14.71 (18.69) versus 5.04 (7.09). All differences were statistically significant (P<.001). Diagnoses for the RSV and control cohorts were respiratory conditions (64% versus 13%), fever (2.7% versus 0.7%), anorexia (2.2% versus 0.6%), lack of normal physiological development (2.8% versus 1.1%; P<.05), overall deaths (8.1% versus 1.6%; P<.001), and sudden death (6.1% versus 0.3%; P<.001).

CONCLUSIONS

RSV hospitalization in healthy premature infants is associated with a significant increase in subsequent health care resource utilization and mortality. Results support prophylaxis of premature infants against RSV hospitalization.