Saudi experts' recommendation for RSV prophylaxis in the era of COVID-19: Consensus from the Saudi Pediatric Pulmonology Association

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and viral pneumonia in pediatrics worldwide. In the Kingdom of Saudi Arabia (KSA), the prevalence of RSV is 23.5% in pediatric patients with acute lower respiratory tract illness. Coronavirus disease (COVID-19) poses critical public health and socioeconomic challenges in KSA. The Saudi Pediatric Pulmonology Association (SPPA), a subsidiary of the Saudi Thoracic Society (STS), developed a task force to determine the potential challenges and barriers to the RSV immunoprophylaxis program during the era of COVID-19 and to compose a practical, nationwide, and multidisciplinary approach to address these challenges. Some of the recommendations to manage these challenges include increasing the number of RSV immunoprophylaxis clinics, drive-thru visits, home-care services, and swift referrals to the RSV immunoprophylaxis program specialists. Additional training is required for healthcare personnel to add RSV immunoprophylaxis to the regular immunization schedule.

Effectiveness of Respiratory Syncytial Virus Immunoprophylaxis in Reducing Bronchiolitis Hospitalizations Among High-Risk Infants

We sought to determine the real-world effectiveness of respiratory syncytial virus (RSV) immunoprophylaxis in a population-based cohort to inform policy. The study population included infants born during 1996-2008 and enrolled in the Kaiser Permanente Northern California integrated health-care delivery system. During the RSV season (November-March), the date of RSV immunoprophylaxis administration and the following 30 days were defined as RSV immunoprophylaxis protected period(s), and all other days were defined as unprotected period(s). Numbers of bronchiolitis hospitalizations were determined using International Classification of Diseases, Ninth Revision, codes during RSV season. We used a proportional hazards model to estimate risk of bronchiolitis hospitalization when comparing infants' protected period(s) with unprotected period(s). Infants who had ever received RSV immunoprophylaxis had a 32% decreased risk of bronchiolitis hospitalization (adjusted hazard ratio = 0.68, 95% confidence interval: 0.46, 1.00) when protected periods were compared with unprotected periods. Infants with chronic lung disease (CLD) had a 52% decreased risk of bronchiolitis hospitalization (adjusted hazard ratio = 0.48, 95% confidence interval: 0.25, 0.94) when protected periods were compared with unprotected periods. Under the new 2014 American Academy of Pediatrics (AAP) guidelines, 48% of infants eligible for RSV immunoprophylaxis on the basis of AAP guidelines in place at birth would no longer be eligible, but nearly all infants with CLD would remain eligible. RSV immunoprophylaxis is effective in decreasing hospitalization. This association is greatest for infants with CLD, a group still recommended for receipt of RSV immunoprophylaxis under the new AAP guidelines.

Bronchiolitis in Infants and Children

Bronchiolitis is among the most common illnesses in infants and children, and is the most common cause for hospitalization in infants in the U.S. This illness can be caused by many viruses, most commonly respiratory syncytial virus. It is diagnosed clinically by history and physical exam findings, with a narrow role for ancillary testing. Management is supportive, with medications demonstrating limited utility in multiple studies. Preventive measures include hand hygiene, breastfeeding, avoiding tobacco smoke exposure, and isolation precautions for hospitalized patients. Palivizumab prophylaxis is recommended for infants with qualifying high risk conditions. Recent evidence-based clinical practice guidelines have been published by the American Academy of Pediatrics to guide diagnosis, treatment, and prevention of bronchiolitis.

Respiratory Syncytial Virus Bronchiolitis in Children

Bronchiolitis is a common lower respiratory tract infection in infants and young children, and respiratory syncytial virus (RSV) is the most common cause of this infection. RSV is transmitted through contact with respiratory droplets either directly from an infected person or self-inoculation by contaminated secretions on surfaces. Patients with RSV bronchiolitis usually present with two to four days of upper respiratory tract symptoms such as fever, rhinorrhea, and congestion, followed by lower respiratory tract symptoms such as increasing cough, wheezing, and increased respiratory effort. In 2014, the American Academy of Pediatrics updated its clinical practice guideline for diagnosis and management of RSV bronchiolitis to minimize unnecessary diagnostic testing and interventions. Bronchiolitis remains a clinical diagnosis, and diagnostic testing is not routinely recommended. Treatment of RSV infection is mainly supportive, and modalities such as bronchodilators, epinephrine, corticosteroids, hypertonic saline, and antibiotics are generally not useful. Evidence supports using supplemental oxygen to maintain adequate oxygen saturation; however, continuous pulse oximetry is no longer required. The other mainstay of therapy is intravenous or nasogastric administration of fluids for infants who cannot maintain their hydration status with oral fluid intake. Educating parents on reducing the risk of infection is one of the most important things a physician can do to help prevent RSV infection, especially early in life. Children at risk of severe lower respiratory tract infection should receive immunoprophylaxis with palivizumab, a humanized monoclonal antibody, in up to five monthly doses. Prophylaxis guidelines are restricted to infants born before 29 weeks' gestation, infants with chronic lung disease of prematurity, and infants and children with hemodynamically significant heart disease.

Respiratory syncytial virus seasonality in Brazil: implications for the immunisation policy for at-risk populations

Respiratory syncytial virus (RSV) infection is the leading cause of hospitalisation for respiratory diseases among children under 5 years old. The aim of this study was to analyse RSV seasonality in the five distinct regions of Brazil using time series analysis (wavelet and Fourier series) of the following indicators: monthly positivity of the immunofluorescence reaction for RSV identified by virologic surveillance system, and rate of hospitalisations per bronchiolitis and pneumonia due to RSV in children under 5 years old (codes CID-10 J12.1, J20.5, J21.0 and J21.9). A total of 12,501 samples with 11.6% positivity for RSV (95% confidence interval 11 - 12.2), varying between 7.1 and 21.4% in the five Brazilian regions, was analysed. A strong trend for annual cycles with a stable stationary pattern in the five regions was identified through wavelet analysis of the indicators. The timing of RSV activity by Fourier analysis was similar between the two indicators analysed and showed regional differences. This study reinforces the importance of adjusting the immunisation period for high risk population with the monoclonal antibody palivizumab taking into account regional differences in seasonality of RSV.

Acute viral bronchiolitis in South Africa: Strategies for management and prevention

Management of acute viral bronchiolitis is largely supportive. There is currently no proven effective therapy other than oxygen for hypoxic children. The evidence indicates that there is no routine benefit from inhaled, rapid short-acting bronchodilators, adrenaline or ipratropium bromide for children with acute viral bronchiolitis. Likewise, there is no demonstrated benefit from routine use of inhaled or oral corticosteroids, inhaled hypertonic saline nebulisation, montelukast or antibiotics. The last should be reserved for children with severe disease, when bacterial co-infection is suspected. Prevention of respiratory syncytial virus (RSV) disease remains a challenge. A specific RSV monoclonal antibody, palivizumab, administered as an intramuscular injection, is available for children at risk of severe bronchiolitis, including premature infants, young children with chronic lung disease, immunodeficiency, or haemodynamically significant congenital heart disease. Prophylaxis should be commenced at the start of the RSV season and given monthly during the season. The development of an RSV vaccine may offer a more effective alternative to prevent disease, for which the results of clinical trials are awaited. Education of parents or caregivers and healthcare workers about diagnostic and management strategies should include the following: bronchiolitis is caused by a virus; it is seasonal; it may start as an upper respiratory tract infection with low-grade fever; symptoms are cough and wheeze, often with fast breathing; antibiotics are generally not needed; and the condition is usually self limiting, although symptoms may occur for up to four weeks in some children.

Montelukast during primary infection prevents airway hyperresponsiveness and inflammation after reinfection with respiratory syncytial virus

RATIONALE

Respiratory syncytial virus (RSV) bronchiolitis in infants may be followed by the development of asthma-like symptoms. Age at first infection dictates consequences upon reinfection. Reinfection of mice initially exposed as neonates to RSV enhanced development of airway hyperresponsiveness (AHR), eosinophilic inflammation, and mucus hyperproduction. RSV lower respiratory tract disease is associated with activation of the leukotriene pathway.

OBJECTIVES

To determine the effects of montelukast (MK), a cysteinyl leukotriene (cysLT) receptor antagonist, in primary and secondary RSV-infected newborn and adult mice.

METHODS

BALB/c mice were infected with RSV at 1 week (neonate) or 6 to 8 weeks (adult) of age and reinfected 5 weeks later. MK was administered 1 day before the initial infection and through Day 6 after infection. Seven days after primary or secondary infection, airway function was assessed by lung resistance to increasing doses of inhaled methacholine; lung inflammation, goblet cell metaplasia, and cytokine levels in bronchoalveolar lavage fluid were monitored.

MEASUREMENTS AND MAIN RESULTS

RSV infection induced cysLT release in bronchoalveolar lavage fluid. MK decreased RSV-induced AHR, airway inflammation, and increased IFN-gamma production in primary infected adult and neonatal mice. MK, administered during initial infection of neonates but not during secondary infection, prevented subsequent enhancement of AHR, airway eosinophilia, and mucus hyperproduction upon reinfection.

CONCLUSIONS

MK attenuated the initial responses to primary RSV infection in both age groups and altered the consequences of RSV reinfection in mice initially infected as neonates. These data support an important role for cysLT in RSV-induced AHR and inflammation.

Evaluation of compliance with palivizumab recommendations in a multicenter study of young children presenting to the emergency department with bronchiolitis

OBJECTIVE

Monthly palivizumab injections from November to March decrease risk of respiratory syncytial virus (RSV)-related hospitalization during RSV season in high-risk infants born less than 35 weeks of gestation. Our objective was to investigate compliance with the American Academy of Pediatrics (AAP) recommendations for palivizumab prophylaxis among children who present to the emergency department (ED) with bronchiolitis.

METHODS

Seventeen centers, from 9 US states, performed a prospective, observational study of ED patients less than 2 years with an attending physician diagnosis of bronchiolitis. Researchers conducted a structured interview, followed by a chart review, and a 2-week follow-up phone call.

RESULTS

Of 825 eligible children, 624 (73%) were enrolled. According to AAP recommendations, 35 children (6%) should have received palivizumab, but only 17 (49%; 95% confidence interval, 31%-66%) did. Prophylaxis with palivizumab did not differ by US region (P > 0.50). The ED clinical presentations were similar when comparing those children that did and did not receive prophylaxis (all P > 0.27). Those receiving palivizumab were more likely to come to the ED using systemic corticosteroids (22% vs 7%; P = 0.003) and to be treated with corticosteroids in the ED (31% vs 15%; P = 0.02). The 2 groups were at similar risk of hospitalization (52% vs 39%; P = 0.11).

CONCLUSIONS

According to parental report, only half of children presenting to the ED with bronchiolitis who met AAP criteria for palivizumab prophylaxis received this monoclonal antibody. Emergency department visits provide an untapped opportunity for staff to educate families and communicate with PCPs about RSV prophylaxis.

The role of breastfeeding and passive smoking on the development of severe bronchiolitis in infants

AIM

Bronchiolitis is an acute infectious disease of the lower respiratory tract which causes the obstruction of bronchioles in children younger than 2 years. The aim of this study was to investigate the effect of passive smoking alone and in conjunction with breastfeeding on the severity of acute bronchiolitis in infancy and the duration of hospitalisation.

METHODS

We studied 240 consecutive infants aged from 6 to 24 months (137 boys and 103 girls) median age 14 months, who required hospital admission for acute bronchiolitis at the Paediatric Department of Democritus University Hospital, Alexandroupolis, Greece. The outcomes of interest were the severity of bronchiolitis and the duration of hospitalisation.

RESULTS

Among the entire cohort, 122 (50.8%) children presented a severe attack of bronchiolitis. In multivariate regression analysis adjusting for confounding factors, breastfeeding for less than four months (aOR=6.1, 95% CI=3.4-10.7), exposure to environmental tobacco smoke (aOR=2.2, 95% CI=1.1-3.6) and their combination (aOR=16.2, 95% CI=6.0-34.3) showed significant association with severe bronchiolitis and prolonged hospitalisation. Passive smoking did not increase the risk of severe bronchiolitis, when infants breastfed for more than four months (aOR=1.9, 95% CI=0.8-5.1).

CONCLUSION

In conclusion, exposure to environmental tobacco smoke worsens the symptoms and the prognosis of bronchiolitis, while breastfeeding seems to have a protective effect even in children exposed to environmental tobacco smoke.

Advances in the treatment and prevention of severe viral bronchiolitis

Viral bronchiolitis continues to be a major public health problem. Prevention of severe RSV-associated bronchiolitis has been achieved in high-risk infants by passive administration of the humanized monoclonal anti-RSV-F antibody, palivizumab. Development of more potent anti-RSV neutralizing antibodies is underway, and vaccine development continues to progress. Supportive therapy is the mainstay for the treatment of established infection while new antiviral and anti-inflammatory strategies are being explored in preclinical trials.

Infections nosocomiales virales dans un service de pédiatrie : l'exemple des gastroentérites à rotavirus et des bronchiolites à VRS

Nosocomial infections are a preoccupation in a pediatric hospital mainly during the winter with bronchiolitis and gastroenteritis epidemics. We have examined the risk factors of nosocomial infections.

MATERIAL AND METHODS

A prospective study was conducted between November, 1999 and March, 2000 in the infants units of the Le Havre hospital. We systematically listed the admissions and contacted the family after their discharge by phone. A geographic information system was implemented to display the epidemiological data; this software is able to illustrate the sectors at risk.

RESULTS

During the study, 687 infants were hospitalized of whom 458 for bronchiolitis and community-acquired gastroenteritis. Mean age was 5.4 months old. No nosocomial bronchiolitis occurred. Prevalence of nosocomial gastroenteritis was 10% (68 cases including nine after discharge). Infants with nosocomial infection were younger than those with community-acquired infection (6.6 months vs. 11.2 months, P < 0.01). The mean length of stay was longer in nosocomial infection (7.7 vs. 4.1 days, P < 0.05). Among the infants with bronchiolitis, 16% have developed nosocomial intestinal infections (RR = 2.65, IC: 1.59-4.4; P < 0.01). The geographic analysis pointed the area with nosocomial risk (bedroom without water, nearness of nurse office and games room).

CONCLUSION

Geographic information system is a part of the quality control system and may have some interaction effect on final decision making. Incidence of nosocomial infections showed the need for a prevention strategy in a pediatric hospital.

Safety and efficacy of immune-stimulating complex-based antigen delivery systems for neonatal immunisation against respiratory syncytial virus infection

To protect against human respiratory syncytial virus (hRSV)-induced bronchiolitis in early infancy, vaccines need to be designed which are effective in the neonatal period. To test the safety and efficacy of adjuvants in neonatal mice, we injected hRSV surface proteins combined with immune-stimulating complexes (ISCOMs) prepared from fractions A, C or A + C of Quillaja saponins. All were well tolerated in adults, but A + C ISCOMS proved lethal in neonates; A or C fractions alone were well tolerated by neonates up to the adult dose. hRSV-ISCOM A induced antibody responses similar to combined fractions, and potent in vitro cytotoxic T cell responses. Adult-like in vitro cytotoxicity against hRSV-infected targets and precursor cytotoxic T cell frequencies were observed within one week of neonatal priming and hRSV-ISCOM A-primed neonates showed virtually complete protection against subsequent viral challenge. hRSV challenge was associated with some pulmonary eosinophilia in both age groups, with higher IL-4 production by lung CD4+ T cells in mice primed as neonates. This was, however, accompanied by only minor (approximately 10%) and transient illness and weight loss. Thus, the identification of hRSV antigen delivery systems with an age-appropriate adjuvanticity/reactogenicity balance may be feasible even in the vulnerable early-life period.

Admission to the intensive care unit for respiratory syncytial virus bronchiolitis: a national survey before palivizumab use

OBJECTIVE

Preterm infants, especially those with chronic lung disease (CLD), are considered more susceptible to severe respiratory illness from respiratory syncytial virus (RSV) infection than healthy term infants, and are therefore targeted for prophylactic administration of immune globulins. The impact of this practice on the more severe cases of bronchiolitis (i.e., pediatric intensive care unit [PICU] admission, mechanical ventilation, mortality) has not been reported to date. The aim of this study was to evaluate PICU admissions, need for mechanical ventilation, and mortality attributable to RSV bronchiolitis in Israel before the introduction of RSV prophylaxis to the country.

DESIGN AND SETTING

Prospective survey of 11 PICUs in Israel during the RSV season (November 2000-March 2001).

PATIENTS

All patients admitted to the PICU because of bronchiolitis, and the subgroups who needed mechanical ventilation or who died, were analyzed for known risk factors, namely, prematurity, CLD, and chronic oxygen dependence.

RESULTS

A total of 105 patients with RSV bronchiolitis met the inclusion criteria, of whom 33 were mechanically ventilated. Most of the patients (84% total admission, 88% ventilated) were born after 32 weeks' gestation, and 89% and 88%, respectively, did not have CLD. Only 16% and 9%, respectively, met any of the American Academy of Pediatrics criteria for RSV prophylaxis, such that 84% of the whole sample and 91% of the ventilated patients were not candidates for RSV prophylaxis. Five patients died, 2 of them with cyanotic heart disease.

CONCLUSIONS

Most of the infants with severe RSV bronchiolitis were born at term and did not have CLD. The great majority of patients admitted to the PICU for bronchiolitis were not candidates for RSV prophylaxis. Administration of RSV prophylaxis to the predefined high-risk population could be expected to yield no significant change in PICU admissions or number of infants needing mechanical ventilation. New risk-stratified guidelines for RSV prophylaxis are needed.

CXCR2 regulates respiratory syncytial virus-induced airway hyperreactivity and mucus overproduction

Severe inflammation and mucus overproduction are partially responsible for respiratory syncytial virus (RSV)-induced disease in infants. Using a murine model, we characterized the virally induced chemokine receptors responsible for mediating the pathophysiological response to RSV infection, we found that CXCR2 mRNA was induced at 4 days after RSV infection. Immunohistochemical staining demonstrated that CXCR2 protein was expressed on alveolar macrophages. Immunoneutralization of CXCR2 resulted in decreased airway hyperreactivity relative to the RSV-infected controls. In addition, there was decreased mucus in the bronchoalveolar lavage fluid, decreased periodic-acid Schiff staining, and significantly less mucus-associated gob-5 mRNA and protein in anti-CXCR2-treated mice. The effects of anti-CXCR2 treatment were not a result of differences in viral clearance or neutrophil influx, as these parameters were comparable in both groups of animals. To confirm our immunoneutralization studies, we performed experiments in CXCR2(-/-) mice. Results in CXCR2(-/-) mice recapitulated results from our immunoneutralization studies. However, CXCR2(-/-) mice also showed a statistically significant decrease in muc5ac, relative to RSV-infected wild-type animals. Thus, CXCR2 may be a relevant target in the pathogenesis of RSV bronchiolitis, since it contributes to mucus production and airway hyperreactivity in our model of RSV infection.

[Chemoprophylaxis with palivizumab in Andalusia (Spain). Results of the 2000-2001 respiratory syncytial virus epidemic]

OBJECTIVE

To assess the hospitalization rate for bronchiolitis in newborns treated with palivizumab in Andalusia.

PATIENTS AND METHODS

We performed a prospective study of 283 neonates and infants who received prophylaxis with palivizumab in Andalusia during the 2000-2001 bronchiolitis epidemic. We also performed a descriptive study of hospitalization for bronchiolitis, classifying patients according to gestational age and whether they had bronchopulmonary dysplasia (BPD).

RESULTS

Most (86.9 %) of the treated patients were born before week 32 of gestation (63 % before week 30) and 38.4 % developed BPD. A total of 10.6 % of palivizumab-treated newborns were hospitalized for bronchiolitis, of which 3.9 % was caused by respiratory syncytial virus (RSV) (4.8 % of patients with BDP and 3.5 % of those without BPD were RSV-positive). Compared with preterm neonates born in weeks 31 or 32 of gestation, palivizumab-treated newborns born before week 31 showed a higher hospitalization rate for bronchiolitis (13.3 % vs 6.3 %; p < 0.05) and that for RSV was three times higher (5.0 % vs 1.6 %; p < 0.05). Age at admission was 5.8 3.2 months. Length of hospital stay was shorter in RSV-positive patients with bronchiolitis (6.7 vs 7.6 days; p > 0.10). Admission to the intensive care unit was required in 0.7 % of patients and in 50 % of those who were RSV-positive. Adverse effects were observed in 5.1 % of palivizumab-treated patients.

CONCLUSION

The marked differences in the perinatal antecedents of patients receiving immunoprophylaxis may explain the variations in the efficacy of palivizumab reported in available studies.

Prevention and treatment of respiratory syncytial virus bronchiolitis and postbronchiolitic wheezing

Respiratory syncytial virus (RSV) is the primary cause of hospitalization for acute respiratory tract illness in general and specifically for bronchiolitis in young children. The link between RSV bronchiolitis and reactive airway disease is not completely understood, even though RSV bronchiolitis is frequently followed by recurrent episodes of wheezing. Therapy with ribavirin does not appear to significantly reduce long-term respiratory outcome of RSV lower respiratory tract infection, and corticosteroid or bronchodilator therapy may possibly improve outcomes only on a short-term basis. No vaccine against RSV is yet available. It is not known whether prophylaxis with RSV intravenous immune globulin or palivizumab can reduce postbronchiolitic wheezing.

Respiratory syncytial virus immune globulin: decisions and costs

A decision analysis was used to evaluate the economic effectiveness of respiratory syncytial virus immune globulin (RSVIG) prophylaxis on selected pediatric populations at risk for developing RSV bronchiolitis or all respiratory illness-related hospitalizations. We compared costs, outcomes, and cost-effectiveness of administering RSVIG to no treatment in different pediatric populations, including those at risk of developing RSV-bronchiolitis and those at risk of developing any respiratory illness-related hospitalization. We observed that if only infants at high risk of severe RSV infections received treatment with RSVIG, a calculated cost saving of about 27,000 dollars per hospitalization prevented were realized. If the Food and Drug Administration (FDA)-approved indications for RSVIG were followed, the cost to prevent one hospitalization due to RSV bronchiolitis would be over 53,000 dollars. If the aim, however, was to prevent all respiratory illness-related hospitalizations for this broader population, a much lower cost (4,000 dollars) to prevent one hospitalization would result. In this situation, cost neutrality was possible, with a therapy cost of 2,843 dollars compared to the actual average therapy cost of 4,444 dollars. Sensitivity analysis showed that the model was relatively insensitive to all variables, with the exceptions of costs related to RSVIG and intensive care unit (ICU) admissions. We conclude that RSVIG resulted in cost savings if therapy were reserved for the infants who are at highest risk for developing severe RSV infections. RSVIG is not cost-effective for preventing RSV bronchiolitis when used according to the FDA-approved indications. Education that emphasizes frequent hand-washing, avoidance of passive smoking, and lessening exposure to sick children remains the least expensive prevention tool.

[Epidemiology of infant bronchiolitis in France]

Respiratory syncytial virus (RSV) bronchiolitis has become a major public health concern in France during the last decade. This winter epidemic mobilizes each year considerable means through the private ambulatory and public hospital nets. The epidemiology of RSV bronchiolitis remains difficult to characterize because of the lack of consensus for its definition. Several French studies are described here which suggest an increase in severity of the epidemics since 10 years in France. Peaks are more important each year and involve younger patients. This phenomenon does not concern other winter epidemics such as rotavirus gastroenteritis or influenza in infants. A policy of prevention of RSV bronchiolitis seams to be necessary in our country in the future.

Respiratory syncytial virus infection in high risk infants and the potential impact of prophylaxis in a United Kingdom cohort

BACKGROUND

Bronchiolitis caused by respiratory syncytial virus (RSV) is an important cause of morbidity in ex-premature infants. In a randomised placebo controlled trial monoclonal antibody prophylaxis showed a 55% reduction in relative risk of hospital admission for these high risk infants, against a background incidence of 10.6 admissions per 100 high risk infants.

AIMS

To follow a cohort of high risk infants in order to assess hospitalisation rate from RSV and the potential impact of prophylaxis for these patients in a UK local health authority.

METHODS

A cohort of high risk infants from a local health authority were followed over the 1998/99 and 1999/2000 RSV seasons. The high risk population was defined as infants who, at the beginning of the seasons studied, were: (1) under 6 months old and born prior to 36 weeks gestation with no domiciliary oxygen requirement; or (2) under 24 months of age and discharged home in supplemental oxygen. All admissions with bronchiolitis during the season were identified.

RESULTS

A total of 370 high risk infants were identified for the 1998/99 season and 286 for the following year. Over the two years there were 68 admissions. Significantly more admissions occurred from group 2 infants. RSV was identified in 27 cases (four admissions per hundred high risk infants). Prophylaxis may have saved up to pound 195,134 in hospital costs over the two years, but would have cost pound 1.1 million in drug acquisition costs.

CONCLUSIONS

Careful consideration of risk factors is needed when selecting infants for RSV prophylaxis.

Prevention of bronchiolitis

This review evaluates the current situation and long-term prospects for containment of human respiratory syncytial virus (HRSV) infection and bronchiolitis in infancy. The biology and immunopathology of HRSV infection are complex. Initial attempts to control HRSV infection using a conventional formalin-inactivated vaccine had the unexpected outcome that the disease was potentiated in some vaccinees experiencing natural HRSV infection at a later date. Much effort has been devoted to defining the nature of protective immunity, and several candidate sub-unit and live attenuated vaccines have been developed by empirical and semi-empirical routes, and most recently by reverse genetics. None has yet received approval for clinical use, and attention has switched from active to passive immunization. Both concentrated human immune globulin (RespiGam) and a humanized monoclonal antibody (Palivizumab) have been approved for clinical use. On grounds of cost-effectiveness these treatments are recommended only for treatment of high-risk infants. An effective antiviral is not yet available.

Nedocromil sodium inhibits canine adenovirus bronchiolitis in beagle puppies

Nedocromil sodium is a nonsteroidal anti-inflammatory drug used to control asthmatic attacks. Our hypothesis is that nedocromil sodium inhibits virus-induced airway inflammation, a common trigger of asthma. We nebulized nedocromil sodium into beagle dogs (n = 10, mean +/- SEM ages: 149 +/- 13 days) before and after inoculation with canine adenovirus type 2 (CAV2). Control dogs (n = 10) received saline aerosols and were either infected with CAV2 (Sal/CAV2, n = 7, mean +/- SEM ages: 140 +/- 11 days) or were not infected (Sal/Sal, n = 3, ages: 143 +/- 0 days). All dogs were anesthetized with choralose (80 mg/kg i.v.), intubated, and mechanically ventilated. Pulmonary function tests and bronchoalveolar lavage (BAL) were performed using standard techniques. Pulmonary function tests revealed no significant change between the nedocromil sodium and non-nedocromil-treated groups. The percentage of infected bronchioles was quantitated as the number of inflamed airways of 40 bronchioles examined times 100 for each dog. Nedocromil-treated dogs had significantly (p < 0.05) less mucosal inflammation (mean +/- SEM, 39% +/- 5%), epithelial denudation (36% +/- 5%), and BAL neutrophilia (11 +/- 3) than did Sal/CAV2 dogs (51% +/- 6%, 57% +/- 4%, and 33% +/- 8%, respectively). We concluded that pretreatment with nedocromil sodium aerosols attenuated CAV2-induced airway inflammation in these beagle puppies.

Prophylaxis against respiratory syncytial virus in premature infants

Postconceptional age was studied in 33 mechanically ventilated preterm infants with respiratory syncytial virus (RSV) bronchiolitis. Preterm infants without chronic lung disease had an increased risk of severe RSV infection until a postconceptional age of 44 weeks.

The effect of IL-12 treatment on vaccine-enhanced illness during infection with respiratory syncytial virus

In humans and mice, sensitisation to respiratory syncytial virus (RSV) antigens can result in severe inflammatory lung disease during subsequent infection with the virus. Although specific antiviral T cells are thought to be responsible for this augmentation of disease, the precise role of different functional subsets is unknown. BALB/c mice sensitised to the major surface glycoprotein (G) of RSV expressed by recombinant vaccinia virus develop Th2-driven lung eosinophilia after intranasal challenge with the virus. Mice treated with IL-12 at various times during vaccination and challenge, had reduced vaccine-induced lung eosinophilia but increased total pulmonary lymphoid cell infiltration. Intracellular cytokine analysis showed that interferon-gamma production during challenge was increased and IL-4 and IL-5 reduced by IL-12 treatment. Though IL-12 treatment reduced lung eosinophilia, illness (as assessed by weight loss) was not eliminated and sometimes increased. Reversing Th2-associated pathology with IL-12 does not necessarily benefit the host.

A comparison of ganciclovir and acyclovir to prevent cytomegalovirus after lung transplantation

In an attempt to modify the sequelae of cytomegalovirus (CMV) infections after lung transplantation, 25 allograft recipients were randomized to either ganciclovir 5 mg/kg once a day 5 d/wk (Group G) or acyclovir 800 mg four times a day (Group A). All subjects received ganciclovir during postoperative Weeks 1 through 3, and they were then given either A or G regimens until Day 90. At termination of study enrollment, the cumulative incidence of all CMV infections (including seroconversions) was increased in Group A compared with that in Group G (75% versus 15%, p < 0.01), as was the incidence of overt CMV shedding and/or pneumonitis (50% versus 15%, p < 0.043). In comparison with those in Group G, subjects in Group A were also afflicted with an increased prevalence of obliterative bronchiolitis (OB) during the first year after transplantation (54% versus 17%, p < 0.033). Intravenous catheters for ganciclovir administration resulted in four complications among three of the subjects in Group G (23%). The short-term benefits of ganciclovir were ultimately limited, moreover, in that cumulative rates of CMV and prevalence of OB are now similar in both treatment groups after approximately 2 yr of observation. We conclude that prolonged ganciclovir prophylaxis decreases the early incidence of CMV and OB among lung transplant recipients, but these effects are of finite duration. Although CMV prevention appears to have considerable potential value in this population, definitive viral prophylaxis will require development of protracted or repeated treatment regimens, or longer-acting agents.

Respiratory syncytial virus: virology, diagnosis, and vaccination

Attempts to develop a respiratory syncytial virus vaccine have revealed the antigenic heterogeneity of the virus and have highlighted the difficulties of inducing protective responses in very young infants. Of the two subgroups of the virus, A and B, that cocirculate, A appears to be the most aggressive in infants, but protection against both will be required. Although a degree of protection is transferred from mother to the infant via the placenta and by breast feeding, the mechanisms of protection remain ill-understood and early hopes of exploiting this phenomenon have not been realized. The immune response to the virus in the very young is depressed but disease severity is not demonstrably linked to failure to control virus replication. Rather, immune mechanisms contribute directly to the development of bronchiolitis. The involvement of the immune response in the pathologic process increases the hazards of vaccination. Research is currently focused on the definition of viral epitopes necessary to induce only a protective immune response and their incorporation into a suitable vaccine vector.

Immunoprophylaxis of infections with respiratory syncytial virus: observations and hypothesis

Infections with respiratory syncytial virus (RSV) may cause substantial morbidity and increased mortality in neonates and infants, especially those born before term and/or with pulmonary or cardiac disease. Humoral immunity was long thought to play only a small role in prevention, reduction of severity, or recovery from RSV infections of the lower respiratory tract. We recently performed a series of experiments in RSV-infected cotton rats, owl monkeys, and human infants to assess the role of humoral immunity in the prevention or recovery from RSV infections. This report summarizes studies utilizing intravenous IgG (IVIG) administered parenterally or topically (into the lower airway) for prophylaxis or treatment of RSV infections of the lower respiratory tract. The prophylactic administration (parenteral or topical) of IVIG to cotton rats or its therapeutic administration to RSV-infected cotton rats, owl monkeys, or humans significantly reduced RSV replication. The reductions in titers of virus correlated positively with titers of RSV-neutralizing antibody. Clinical trials are indicated to determine whether parenteral IVIG prophylaxis might prevent serious RSV infections in high-risk infants.

Vitamin A status of children with a history of respiratory syncytial virus infection in infancy

In order to extend our earlier observation that children who experience frequent respiratory episodes may benefit from Vitamin A supplementation, 206 children aged 2-7 years who had been hospitalized for bronchiolitis during infancy were randomized into a controlled trial of Vitamin A supplementation. Of these, 149 met the criteria of protocol compliance after 12 months of follow-up. Mean plasma retinol at baseline was 39.2 micrograms/100 ml (s.e.m. = 1.0) and did not increase after 12 months (mean = 36.0 micrograms/100 ml, s.e.m. = 0.7) despite the older age of the cohort. The range observed (11.7-73.9 micrograms/100 ml) included some children at risk of marginal Vitamin A deficiency. Mean plasma retinol levels were 20% lower than those of children experiencing frequent respiratory episodes recorded earlier. Oral supplementation did not change plasma retinol levels, nor did it affect respiratory morbidity.

Ribavirin administration to infants receiving mechanical ventilation

Aerosolized ribavirin was administered to 12 infants with bronchiolitis who were receiving mechanical ventilation. All patients had a history of cardiac or pulmonary disease and developed severe respiratory failure during their infection. We developed a method for ribavirin administration and patient monitoring that included timed circuit valve and tubing changes to avoid obstruction by precipitated drug, frequent endotracheal tube suctioning, and constant observation of the patient and ventilator. All patients were successfully treated. We conclude that ribavirin can be safely administered to infants receiving mechanical ventilation.

Management of bronchiolitis

The incidence, etiology, epidemiology, clinical presentation, treatment, prognosis, and prevention of bronchiolitis are discussed with a critical evaluation of the available studies on various therapeutic approaches. Bronchiolitis is a lower respiratory-tract viral infection that affects 6-10% of all children below two years of age. Respiratory syncytial virus (RSV) is the usual pathogen. The symptoms range from mild wheezing to severe respiratory distress. An infected child usually has a fever, a rapid pulse, an increased breathing rate, and difficulty in breathing. Because most of the infants hospitalized with bronchiolitis have hypoxemia, the administration of oxygen is the mainstay of therapy. Correct fluid therapy is essential to avoid dehydration and overhydration. Limited data are available on the use of drugs in the management of bronchiolitis. Although a variety of adrenergic drugs, theophylline, and corticosteroids are used, sound efficacy data are lacking, and most studies have documented a lack of therapeutic benefits. One study reported that the combined use of corticosteroids and albuterol may be beneficial in severely ill patients. Recent studies have shown that the continuous administration of ribavirin may decrease viral shedding. Antibiotics are not indicated unless a secondary bacterial infection is present. Oxygen and fluid therapy have a clear role in the management of patients with bronchiolitis; however, no specific guidelines are available for the use of drugs in the treatment of these patients.

Prevention of infections with respiratory syncytial virus: the hopes and hurdles ahead

Control of infections due to respiratory syncytial virus (RSV) by immunization poses special problems. First, the peak period of serious illness due to RSV is during the first few months of life, and thus a vaccine would have to be administered during the neonatal period. Second, we understand little of the pathogenesis of and immunity to RSV disease in newborns, and an immune reaction may even play a role in the development of the lower respiratory tract disease seen in infancy. Third, immunity to RSV is imperfect even after naturally acquired, severe infection of the lower respiratory tract. Therefore, it is difficult to envision a vaccine that is safe in the infant and that will engender more complete immunity than the disease itself. However, if the goals are limited to protection of certain high-risk groups or to protection of infants during the first year of life only, immunization might be both feasible and effective in reducing the morbidity and mortality associated with this ubiquitous virus.