Effectiveness of palivizumab prophylaxis in infants and children in Florida

Respiratory syncytial virus reinfections among infants and young children in the United States, 2011-2019

BACKGROUND

Although respiratory syncytial virus (RSV) immunoprophylaxis is recommended for high-risk infants, the American Academy of Pediatrics (AAP) recommends against immunoprophylaxis in the same season following a breakthrough hospitalization due to limited risk for a second hospitalization. Evidence in support of this recommendation is limited. We estimated population-based re-infection rates from 2011-2019 in children <5 years since RSV risk remains relatively high in this age group.

MATERIALS AND METHODS

Using claims data from private insurance enrollees, we established cohorts of children <5 years who were followed to ascertain annual (July 1-June 30) and seasonal (November 1- February 28/29) RSV recurrence estimates. Unique RSV episodes included inpatient encounters with RSV diagnosis ≥30 days apart, and outpatient encounters ≥30 days apart from each other as well as from inpatient encounters. The risk of annual and seasonal re-infection was calculated as the proportion of children with a subsequent RSV episode in the same RSV year/season.

RESULTS

Over the 8 assessed seasons/years (N = 6,705,979) and across all age groups annual inpatient and outpatient infection rates were 0.14% and 1.29%, respectively. Among children with a first infection, annual inpatient and outpatient re-infection rates were 0.25% (95% confidence interval (CI) = 0.22-0.28) and 3.44% (95% CI = 3.33-3.56), respectively. Both infection and re-infection rates declined with age.

CONCLUSION

While medically-attended re-infections contributed numerically only a fraction of the total RSV infections, re-infections among those with previous infection in the same season were of similar magnitude as the general infection risk, suggesting that a previous infection may not attenuate the risk for a re-infection.

Effectiveness of palivizumab in preventing respiratory syncytial virus infection in high-risk children

To date, there is no consensus regarding palivizumab prophylaxis for respiratory syncytial virus infection. The purpose of this study is to assess the effectiveness of palivizumab prophylaxis to prevent respiratory syncytial virus-related infection consultations and hospitalizations in high-risk children <2 y. We studied children <2 y of age with risk factors who had indication of palivizumab prophylaxis over eight epidemic seasons (2011–2012 to 2018–2019) in Navarra, Spain. Children positives for respiratory syncytial virus by reverse-transcription polymerase chain reaction were compared to negative testers. Palivizumab was indicated in 1,214 children <2 y of age with risk factors during 2011–2012 to 2018–2019 seasons. A total of 142 high-risk children tested for respiratory syncytial virus were included in the study. From the 35 respiratory syncytial virus-positive confirmed cases, 20 (57%) had received palivizumab versus 82 (77%) from the 107 negative controls. The effectiveness of prophylactic palivizumab was 70% (95% CI, 19%-90%) in preventing confirmed clinical infection and 82% (95% CI, 29%-96%) in preventing hospitalized cases. Our results show that palivizumab is notably effective for preventing laboratory-confirmed cases of respiratory syncytial virus and hospitalization in high-risk children <2 y of age. For children who have received palivizumab, the risk of getting sick remains high; thus, other preventive measures are necessary.

Calibration of Chronic Lung Disease Severity as a Risk Factor for Respiratory Syncytial Virus Hospitalization

BACKGROUND

Guidelines assume children with chronic lung disease (CLD) who require medical support within 6 months before the second respiratory syncytial virus (RSV) season remains at high risk of severe RSV disease. We determined the number of days since the last treatment (DSL) when the risk of RSV hospitalization among children with CLD becomes equivalent to the risk for those not qualified for immunoprophylaxis.

METHODS

The study cohort was assembled using Medicaid billing records from 1999 to 2010 linked to Florida and Texas birth certificate records. We developed DSL-trend discrete time logistic regression models within a survival analysis framework, adjusting for use of immunoprophylaxis, to compare the hospitalization risk of CLD infants at 4 age points to that of term infants at 1 month of age with siblings.

RESULTS

The study cohort included 858 830 healthy term and 5562 preterm infants with CLD. Among 1-month-old term infants, the RSV hospitalization risk averaged across all covariate strata was 14.8 (95% confidence interval [CI], 13.5-16.1) per 1000 patient season-months. Risk for preterm CLD children reached the threshold derived from term infants when DSL was 76 (95% CI, 22-198.5), 52 (95% CI, 6.5-123), 35 (95% CI, 0-93.5), and 12 (95% CI, 0-61.5) at the respective ages of 12, 15, 17.2, and 21 months.

CONCLUSIONS

The 180-day threshold used to define CLD severity at season start can be shortened to 120 days, 90 days, and 60 days for children with CLD at age 15, 17.2, and 21 months, respectively.

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.

Association of Age With Risk of Hospitalization for Respiratory Syncytial Virus in Preterm Infants With Chronic Lung Disease

IMPORTANCE

It is unknown whether the age threshold (≤24 months) for preterm infants with chronic lung disease (CLD) to receive immunoprophylaxis for respiratory syncytial virus (RSV) as currently recommended by American Academy of Pediatrics guidelines correctly identified infants at higher risk for hospitalization for RSV.

OBJECTIVE

To determine the age when the risk of hospitalization for RSV among preterm infants with CLD becomes equivalent to the risk for healthy, 1-month-old term infants who do not qualify for immunoprophylaxis.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study was conducted of 1 018 593 healthy term infants and 5181 preterm infants with CLD using Medicaid billing records (Medicaid Analytic eXtract files) from January 1, 1999, to December 31, 2010, linked to Florida and Texas birth and death certificates.

EXPOSURES

Age-trend discrete time logistic regression models within a survival analysis framework were developed, adjusting for covariates including the use of immunoprophylaxis, to compare the risk of hospitalization of preterm infants (<32 weeks' gestational age) with CLD at 3 through 34 months of age with the risk of hospitalization of term infants (37-41 weeks' gestational age) at 1 month of age.

MAIN OUTCOMES AND MEASURES

Age at which risk of hospitalization for RSV among preterm infants with CLD equals the risk for healthy term infants at age 1 month.

RESULTS

The study cohort included 1 018 593 healthy term infants and 5181 preterm infants with CLD; because patients could reenter the cohort for a second or third season, the total study cohort consisted of 1 880 531 healthy term infant-seasons (926 206 girls and 954 325 boys; mean [SD] age at first season entry, 12.6 [9.6] months) and 8680 CLD infant-seasons (3519 girls and 5161 boys; mean [SD] age at first season entry, 15.1 [9.1] months). Among term infants with siblings, the risk of hospitalization for RSV averaged across all covariate strata was 9.0 (95% CI, 8.4-9.6) per 1000 patient season-months at 1 month of age. The risk of hospitalization for RSV among preterm infants with CLD became similar to that of 1-month-old term infants at an age of 18.5 months (95% CI, 15.6-22.8).

CONCLUSIONS AND RELEVANCE

The age threshold at which the risk of hospitalization for RSV among qualifying preterm infants with CLD approximates that of healthy term infants supports the current American Academy of Pediatrics practice guideline recommending RSV prophylaxis until a maximum of 24 months of age.

Vitamin D deficiency and acute lower respiratory infections in children younger than 5 years: identification and treatment

INTRODUCTION

Acute lower respiratory infection (ALRI) is a leading cause of childhood mortality. Research suggests that vitamin D deficiency (VDD) puts children at risk for ALRI. The purpose of this review is to examine ALRI and VDD in children 5 years and younger. Common etiologies, diagnosis, prevention, treatment of ALRI, and recommendations for vitamin D supplementation are summarized.

METHOD

Databases were searched for studies investigating VDD and ALRI in children. Independent reviewers assessed the internal validity of the studies.

RESULTS

Of 18 studies examined, VDD was found to be associated with increased risk or severity of ALRI in 13 studies; associations were not found in 4 studies. In one study it was found that high maternal vitamin D levels was associated with ALRI in infants.

DISCUSSION

Vitamin D supplementation is a low-cost, low-risk intervention that providers should consider for children, especially those at high risk for ALRI. Practitioners should follow current recommendations when prescribing vitamin D supplementation for infants and children.

Partial palivizumab prophylaxis and increased risk of hospitalization due to respiratory syncytial virus in a Medicaid population: a retrospective cohort analysis

Background

Infection with respiratory syncytial virus (RSV) is common among young children insured through Medicaid in the United States. Complete and timely dosing with palivizumab is associated with lower risk of RSV-related hospitalizations, but up to 60% of infants who receive palivizumab in Medicaid population do not receive full prophylaxis. The purpose of this study was to evaluate the association of partial palivizumab prophylaxis with the risk of RSV hospitalization among high-risk Medicaid-insured infants.

Methods

Claims data from 12 states during 6 RSV seasons (October 1^st to April 30^th in the first year of life in 2003–2009) were analyzed. Inclusion criteria were birth hospital discharge before October 1^st, continuous insurance eligibility from birth through April 30^th, ≥ one palivizumab administration from August 1^st to end of season, and high-risk status (≤34 weeks gestational age or chronic lung disease of prematurity [CLDP] or hemodynamically significant congenital heart disease [CHD]). Fully prophylaxed infants received the first palivizumab dose by November 30^th with no gaps >35 days up to the first RSV-related hospitalization or end of follow-up. All other infants were categorized as partially prophylaxed.

Results

Of the 8,443 high-risk infants evaluated, 67% (5,615) received partial prophylaxis. Partially prophylaxed infants were more likely to have RSV-related hospitalization than fully prophylaxed infants (11.7% versus 7.9%, p< 0.001). RSV-related hospitalization rates ranged from 8.5% to 24.8% in premature, CHD, and CLDP infants with partial prophylaxis. After adjusting for potential confounders, logistic regression showed that partially prophylaxed infants had a 21% greater odds of hospitalization compared with fully prophylaxed infants (odds ratio 1.21, 95% confidence interval 1.09-1.34).

Conclusions

RSV-related hospitalization rates were significantly higher in high-risk Medicaid infants with partial palivizumab prophylaxis compared with fully prophylaxed infants. These findings suggest that reduced and/or delayed dosing is less effective.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2431-14-261) contains supplementary material, which is available to authorized users.

Respiratory syncytial virus--a comprehensive review

Respiratory syncytial virus (RSV) is amongst the most important pathogenic infections of childhood and is associated with significant morbidity and mortality. Although there have been extensive studies of epidemiology, clinical manifestations, diagnostic techniques, animal models and the immunobiology of infection, there is not yet a convincing and safe vaccine available. The major histopathologic characteristics of RSV infection are acute bronchiolitis, mucosal and submucosal edema, and luminal occlusion by cellular debris of sloughed epithelial cells mixed with macrophages, strands of fibrin, and some mucin. There is a single RSV serotype with two major antigenic subgroups, A and B. Strains of both subtypes often co-circulate, but usually one subtype predominates. In temperate climates, RSV infections reflect a distinct seasonality with onset in late fall or early winter. It is believed that most children will experience at least one RSV infection by the age of 2 years. There are several key animal models of RSV. These include a model in mice and, more importantly, a bovine model; the latter reflects distinct similarity to the human disease. Importantly, the prevalence of asthma is significantly higher amongst children who are hospitalized with RSV in infancy or early childhood. However, there have been only limited investigations of candidate genes that have the potential to explain this increase in susceptibility. An atopic predisposition appears to predispose to subsequent development of asthma and it is likely that subsequent development of asthma is secondary to the pathogenic inflammatory response involving cytokines, chemokines and their cognate receptors. Numerous approaches to the development of RSV vaccines are being evaluated, as are the use of newer antiviral agents to mitigate disease. There is also significant attention being placed on the potential impact of co-infection and defining the natural history of RSV. Clearly, more research is required to define the relationships between RSV bronchiolitis, other viral induced inflammatory responses, and asthma.

Palivizumab immunoprophylaxis effectiveness in children with cystic fibrosis

BACKGROUND

Evidence on the effectiveness of respiratory syncytial virus (RSV) immunoprophylaxis with palivizumab in children with cystic fibrosis (CF) is lacking.

METHODS

We utilized Medicaid Extract files from 27 states from 1999 to 2006 linked to the National Cystic Fibrosis Registry to establish a cohort of children 0-2 years with CF diagnosis. Eligible children entered the cohort after CF diagnosis and after RSV season onset, and were followed until season end, second birthday, death, or hospitalizations for reasons other then the study outcome. Two outcomes were examined: hospitalization for RSV infections (RSV-ha), or hospitalization for acute respiratory infections (ARI-ha). Palivizumab exposure was defined based on pharmacy or procedure claims as current (claim date plus 30 days), former (day 31-60 after a claim), and no exposure (days before the first or >60 days after any claim). Both outcomes were examined in a Cox regression model, adjusting for RSV risk factors and CF severity via exposure propensity score.

RESULTS

The matched cohort included 1,974 infants (2,875 infant seasons), who experienced 32 RSV-ha and 212 ARI-ha (3.9 and 26.2/1,000 season months, respectively). Compared to periods of no use, the adjusted hazard ratio for current use was 0.57 (95% confidence interval [CI]: 0.20-1.60) for RSV-related hospitalization and 0.85 (95% CI: 0.59-1.21) for ARI-related hospitalization. Each month of increasing age reduced the ARI-ha by 5.8%.

CONCLUSION

RSV hospitalization incidence was low suggesting either little contribution of the virus to respiratory infections in patients with CF or lack of RSV testing. Unadjusted and adjusted RSV-hospitalization incidence rates suggested potentially positive effects of palivizumab, but results were inconclusive due to small event rates. Hospitalizations for acute respiratory illness with possible RSV contribution showed no association with palivizumab use, suggesting limited overall effect of palivizumab. Younger age greatly increased infection risk.

Respiratory viral and pneumococcal coinfection of the respiratory tract: implications of pneumococcal vaccination

The interactions between Streptococcus pneumoniae and other respiratory pathogens have been studied in vitro, in animal models and in humans - including epidemiologic and vaccine probe studies. Interactions of pneumococcus with respiratory viruses are common, and many mechanisms have been suggested to explain this phenomenon. The aim of this review is to explore pneumococcal interactions with respiratory viruses and consider the potential role that the pneumococcal polysaccharide-protein conjugate vaccine may play in modifying pneumococcal-respiratory viral interactions.