Development of local guidelines for prevention of respiratory syncytial viral infections

Predicting respiratory syncytial virus hospitalisation in Australian children

BACKGROUND

There is limited information on respiratory syncytial virus infections among Australians, particularly those of Indigenous descent.

AIM

This study identifies groups of infants at risk of hospitalisation with respiratory syncytial virus-positive lower respiratory tract infection who may be targeted for prevention with palivizumab.

METHODS

Case control study: the case notes of 271 children with cases of respiratory syncytial virus-positive lower respiratory tract infection admitted to The Townsville Hospital were studied for risk factors. Controls were chosen randomly from babies born in The Townsville Hospital during that period. Multiple logistic regression analysis and classification and regression tree analysis were used to identify risk factors.

RESULTS

Multiple logistic regression analysis identified birthweight <2500 g, maternal parity and marital status to be independent predictors of hospitalisation with respiratory syncytial virus-positive lower respiratory tract infection. Classification and regression tree analysis identified babies born weighing <2500 g who possessed older siblings to be at highest risk. Single mothers and smoking were additional risk factors. Indigenous babies were significantly more likely to be exposed to all of the identified risk factors.

CONCLUSION

Babies born weighing <2500 g (especially with siblings) could be targeted for prevention. All Indigenous babies should be considered at high risk because of their exposure to multiple risk factors.

Cost-effectiveness of respiratory syncytial virus prophylaxis with palivizumab

BACKGROUND

A monoclonal antibody, palivizumab, directed against respiratory syncytial virus (RSV) has been shown to decrease hospitalisation rates. Because of its expense, the cost-effectiveness of this agent should be determined for high-risk groups.

AIM

To determine characteristics of RSV infection in Townsville and the economic feasibility of palivizumab immunoprophylaxis in high-risk groups.

METHODS

Cases of RSV-positive bronchiolitis were retrospectively identified. Cases were grouped according to recognised risk factors. The hypothetical costs of palivizumab immunoprophylaxis for infants at risk were calculated.

RESULTS

The rate of hospitalisation with RSV-positive lower respiratory tract infection was 22 per 1000 live births but increased to 50 per 1000 among Indigenous babies born weighing <2500 g. The cost of preventing an admission in each of the identified high-risk groups, based on drug costs alone, ranged from AD 69,861 to AD 88,547.

CONCLUSION

Palivizumab was not cost-effective in the prophylaxis of RSV in the high-risk group of infants tested here.

Low incidence of respiratory syncytial virus hospitalisations in haemodynamically significant congenital heart disease

BACKGROUND

Haemodynamically significant congenital heart disease (CHD) is a risk factor for severe respiratory syncytial virus (RSV) disease in young children. Population based data on the incidence of RSV hospitalisations in CHD patients are needed to estimate the potential usefulness of RSV immunoprophylaxis using palivizumab.

AIMS

(1) To obtain population based RSV hospitalisation rates in children <24 months of age with CHD. (2) To compare these rates with non-CHD patients and with previous studies. (3) To determine the number of patients needed to treat (NNT) with palivizumab to prevent one RSV hospitalisation.

METHODS

Six year, longitudinal, population based study at an institution, which is the sole provider of primary to tertiary in-patient care for a precisely defined paediatric population.

RESULTS

RSV hospitalisation rates (per 100 child-years) in CHD patients aged <6, <12, 12-24, and <24 months of age were 2.5 (95% CI 0.8 to 5.6), 2.0 (0.8 to 3.8), 0.5 (0.1 to 1.8), and 1.3 (0.6 to 2.3), respectively, and the relative risk (RR) in comparison with non-CHD patients was 1.4 (0.6 to 3.1), 1.6 (0.8 to 3.2), 2.7 (0.7 to 9.7), and 1.8 (1.0 to 3.3), respectively. NNT was between 80 (35 to 245) and 259 (72 to 2140) for various age groups.

CONCLUSION

RSV hospitalisation rates in CHD patients were fourfold lower than reported from the USA. Based on these low rates and RR, unrestricted use of palivizumab does not appear to be justified in this study area.

Palivizumab prophylaxis and hospitalization for respiratory syncytial virus disease in the Stockholm infant population, 1999 through 2002

BACKGROUND

There are few independent, population-based reports that estimate the risk of hospitalization of respiratory syncytial virus (RSV)-infected infants before and during the palivizumab era. We present figures from the greater Stockholm area during the three seasons after the introduction of palivizumab and relate them to data based on 1400 hospitalizations for RSV disease in the same population area during 1987 through 1998.

METHODS

The number of births, neonatal complications and palivizumab prescriptions was obtained. We retrieved information about all infant hospitalizations for confirmed RSV infections with risk factors and complications. Chronic lung disease (CLD) in preterm infants was defined as oxygen dependency beyond 36 weeks of postconceptional age.

RESULTS

Eight hundred eighteen infants (1.3% of the population) were hospitalized for confirmed RSV infection. The hospitalization rates were 3.7% (24 of 642) among preterm infants with gestational age <33 weeks without CLD and 7.2% (14 of 195) in those with CLD. Palivizumab had been given to 235 infants, usually those with CLD and in need of continuous oxygen or steroid treatment or the <6 month-old infants with extremely preterm birth (gestational age <26 weeks). The risk of hospitalization for RSV disease was low, but this was the case also before the introduction of palivizumab.

CONCLUSIONS

In countries with a low baseline risk of hospitalization for RSV infection, the benefit of palivizumab might not justify the cost of its widespread use. We advocate defining more rigorous prescription criteria.

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.

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.

Cost of hospitalization for respiratory syncytial virus chest infection and implications for passive immunization strategies in a developing nation

Respiratory syncytial virus (RSV) chest infection is a common cause of hospitalization in the very young child. The aim of this study was to determine the direct cost of resource utilization in the treatment of children hospitalized with RSV chest infection and the potential cost-savings with passive immunization for high-risk infants. An audit of the hospital resource consumption and its costs was performed for 216 children aged < 24 mo admitted with RSV chest infection between 1995 and 1997. The cost-saving potential of passive immunization using monoclonal RSV antibodies during the RSV season was determined by assuming an 0.55 efficacy in hospitalization reduction when administered to "high-risk" infants according to the guidelines outlined by the American Academy of Pediatrics (AAP). The hospital treatment cost of 1064 bed-days amounted to USD 64 277.70. Each child occupied a median of 4.0 bed-days at a median cost of USD 169.99 (IQ1 128.08, IQ3 248.47). Children, who were ex-premature or with an underlying illness were more likely to have a longer hospital stay, higher treatment costs and need for intensive care. Ten (42%) of 24 ex-premature infants fulfilled the recommended criteria for passive immunization. Its use resulted in an incremental cost of USD 31.39 to a potential cost saving of USD 0.91 per infant for each hospital day saved.

CONCLUSION

Ex-prematurity and the presence of an underlying illness results in escalation of the direct treatment cost of RSV chest infection. Current guidelines for use of passive RSV immunization do not appear to be cost-effective if adopted for Malaysian infants.

Palivizumab prophylaxis of respiratory syncytial virus infection in high-risk infants

Palivizumab prophylaxis significantly reduces hospitalization for respiratory syncytial virus (RSV) disease in preterm infants. However, palivizumab is very expensive. Data from a New Zealand cost-effectiveness analysis were considered by representatives of the Infectious Diseases and Immunisation, Fetus and Newborn, and Respiratory Committees of the Paediatric Society of New Zealand. Prophylaxis in all high-risk groups was associated with net cost. The consensus panel recommends that the priority for palivizumab be given to babies discharged on home oxygen with chronic lung disease, followed by babies born at 28 weeks or less gestation.

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.

[Prospective regional study of an epidemic of respiratory syncytial virus (RSV) bronchiolitis]

This prospective study was designed to identify risk factors associated with admission in pediatric intensive care units (PICU) among infants hospitalized for treatment of RSV induced bronchiolitis. This study was population-based and was conducted in Burgundy, a French region with 1,800,000 inhabitants where passive immunoprophylaxis for RSV bronchiolitis was not set up at the time of the study.

RESULTS

From December 1st 1999 to April 30th 2000, 484 infants were hospitalized for RSV bronchiolitis in Burgundy: 19.6% were born prematurely (gestational age [GA] below 37 weeks) and at admission, 68.3% had a postnatal age below six months (mean = 5 +/- 5.9 months; median value = 3 months). The duration of hospitalization was 7.3 +/- 12.4 days (median value = 6 days). Among the 484 infants, 31 (6.4%) needed admission in PICU, eight needed mechanical ventilation (1.7%) and one died (0.2%). Univariate analysis identified anamnestic risk factors associated with admission in PICU: prematurity; low birth weight; past history of neonatal respiratory distress syndrome (RDS); mechanical ventilation for RDS treatment; bronchopulmonary dysplasia (BPD) and congenital heart disease. Multivariate analysis identified three independent factors associated with an increased risk for admission in PICU: GA below 32 weeks; RDS and congenital heart disease.

CONCLUSION

This study suggests that population at risk for severe RSV bronchiolitis with PICU admission should include all very preterm infants with RDS whatever the outcome of RDS (with or without BPD). These epidemiological data could be helpful to set up indications for passive immunoprophylaxis of RSV induced bronchiolitis.

A method for identifying the financial burden of hospitalized infants on families

OBJECTIVES

To describe a method for measuring the direct and indirect costs to families of infants hospitalized with respiratory syncytial virus (RSV).

METHODS

After pretesting and revising a questionnaire, a prospective survey was conducted in multiple tertiary-care hospitals with pediatric intensive care units. Eligible patients were infants less than 12 months old who had not received RSV prophylaxis and were hospitalized with a confirmed RSV infection. All English- and Spanish-speaking caregivers of eligible subjects were asked to participate in a face-to-face, structured interview on the day of hospital discharge regarding hospitalization-related direct and indirect costs. Thirty days later, caregivers were re-interviewed by telephone about their RSV-related costs during the elapsed month. The survey was initiated in February 2000 and continued through April 2001.

RESULTS

In addition to the infants' parents, numerous adults visited 55% of hospitalized infants. In 17% of cases, nonparents missed work to visit the child. Volunteers watched siblings of 26% of the infants. Relying only on closed-ended questions about parents' costs during the hospitalization would have missed important information about child-care volunteers and types of expenses. Follow-up interviews revealed that RSV-related out-of-pocket expenses and missed work continued during the month following discharge.

CONCLUSIONS

Survey instruments should be pretested with potentially eligible subjects. Open-ended questions are needed, because all costs cannot be anticipated. Respondents should be probed for details. This method revealed certain time and financial burdens during and after hospitalization that had not been previously reported in the literature.

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.

Antibodies for the prevention and treatment of viral diseases

This paper reviews current use and evolving role of polyclonal and monoclonal antibody products for the prevention and treatment of viral diseases. Antibodies continue to be indicated for prophylaxis either prior to an anticipated exposure especially in situations of travel, or more commonly following an exposure. The predominant indication for use of antibody products is to prevent infection. With the availability of vaccines for the prevention of chickenpox, hepatitis A, hepatitis B, measles, rabies and smallpox, the role of passive immunization is reserved for susceptible individuals and those at high risk for complications of infection. Risks of transmission of infections associated with use of human plasma-derived products have been reduced by improvements in donor screening and virus removal and inactivation procedures. An additional safety concern has been addressed by the removal of thimerosal as a preservative. Within the last 5 years, two antibodies have been licensed for a viral indication, RespiGam and Synagis both for prevention of respiratory syncytial virus infection. RespiGam is a human plasma derived antibody and Synagis is a humanized monoclonal antibody, the first such antibody to be licensed for an infectious disease indication. CytoGam for prevention of cytomegalovirus infection in kidney transplant patients has recently been granted an expanded indication to include use in lung, liver, pancreas and heart transplant patients. As the use of therapeutics becomes more sophisticated, researchers may find better ways of using antibody products.

Hospitalisation for RSV infection in ex-preterm infants-implications for use of RSV immune globulin

BACKGROUND

Respiratory syncytial virus (RSV) specific immune globulin is now being marketed for prevention of RSV infection in ex-preterm infants. However, there are no published UK data on the morbidity or mortality from RSV in these infants.

AIMS

To determine the morbidity and mortality from RSV infection in a cohort of infants previously treated at a regional neonatal unit, and compare the cost of hospitalisation for RSV with the potential cost of administering RSV immune globulin (RSV-IG) prophylaxis.

METHODS

Infants born at a gestation of less than 32 weeks were studied. Details of admissions for respiratory illness in the first two years of life were collected from hospital records, referring hospitals, and general practitioners.

RESULTS

Data on 82 infants were collected. Up to three RSV seasons were encountered. The hospitalisation rate for confirmed RSV infection for the first season encountered was 4%. Rates of ward and paediatric intensive care unit admission were higher for infants with chronic lung disease. There were no deaths from RSV. RSV-IG would not have been cost effective for most infants.

CONCLUSION

The morbidity and mortality rates from RSV observed in this group do not support the widespread introduction of RSV-IG prophylaxis for ex-preterm infants.