OUP accepted manuscript

Potential public health and economic impact of maternal vaccination with bivalent respiratory syncytial virus prefusion F (RSVpreF) vaccine for the prevention of acute respiratory infection among infants in the United States

BACKGROUND

The U.S. Advisory Committee on Immunization Practices recommends use of bivalent stabilized prefusion F subunit vaccine (RSVpreF) among pregnant persons to protect their infants against lower respiratory tract illness due to RSV (RSV-LRTI).

RESEARCH DESIGN AND METHODS

Using a cohort model depicting clinical outcomes and economic costs of RSV acute respiratory infection (RSV-ARI) among US infants from birth to age 1 year, we evaluated the impact of seasonally administered maternal RSVpreF versus no intervention. Outcomes included cases of medically attended RSV-ARI, RSV-related deaths, medical costs, and indirect costs. Costs were reported in 2023 US$.

RESULTS

Among the 3.7 million US infants aged <12 months each year, a total of 1,148,967 RSV-ARI cases (hospital: 48,384; emergency department [ED]: 246,118; outpatient clinic [OC]: 854,465) were projected to occur, yielding total annual costs of $2.4 billion (direct: $1.7B; indirect: $0.7B). With 54.9% uptake, RSVpreF would prevent 89,908 cases (hospital: 10,308; ED: 20,538; OC: 59,062), corresponding with a $368 million decrease (direct: $286 M; indirect: $81 M) in total 1-year costs.

CONCLUSION

Even with limited uptake and without considering benefits to pregnant persons or reductions in RSV-related sequelae, maternal vaccination with RSVpreF would substantially reduce the public health and economic burden of RSV-ARI in US infants.

Bronchiolitis: Impact of Age and Etiology on Morbidity and Mortality in Previously Healthy Critically Ill Children

This retrospective, multicenter observational study analyzed data from 257 children under 2 years old admitted with viral bronchiolitis to pediatric intensive care units (PICU) at Wolfson Children's Hospital and UFHealth Shands Children's Hospital from January 2020 to March 2022. The study explores viral etiologies and their associations with hospital length of stay (H-LOS), PICU length of stay (P-LOS), and severity markers and scores. Younger age was associated with longer H-LOS and P-LOS (P < .001). Respiratory syncytial virus (RSV) was associated with younger age but not with H-LOS when controlled for age. RSV's impact on H-LOS varied by age (P = .018). Markers of severity did not differ between patients infected with RSV versus those without RSV, or in patients with co-infection versus single infection. In our population, pSOFA performed better than PELOD-2 in disease severity assessment.

Respiratory syncytial virus hospitalisation burden in children below 18 years in six European countries (2016-2023) pre- and post-COVID-19 pandemic

OBJECTIVES

Respiratory syncytial virus (RSV) is a substantial cause of hospital admission in young children and leads to seasonal pressure on pediatric emergency units in most countries. This study aims to assemble national or large-scale data on RSV hospitalisations from six European countries with a standardised approach to provide recent burden data for all children and assess changes since SARS-CoV-2's emergence.

METHODS

We analysed 2016-2023 hospital records from national registries in Denmark, England, Finland, The Netherlands, and Scotland, and from a hospital surveillance network in Spain-Valencia for children below 18 years. We considered separately RSV-coded and RSV laboratory-confirmed cases, comparing them to respiratory tract infections. We studied the temporal evolution of incidence rates and case reporting practices, comparing pre- and post-COVID-19 periods.

RESULTS

Post-COVID-19 observed RSV hospital burden was similar to the pre-COVID-19 one for younger children but higher for the 1-2 years, 3-4 years, and 5-17 years age groups. No change in terms of coding-neither diagnosis nor RSV-coding when RSV was laboratory-confirmed-was detected.

CONCLUSIONS

Hospital RSV burden in children is significant but currently not fully monitorable. Further efforts to harmonise coding practices both within and across countries would improve the quality of future analyses. Additional data in future seasons should complement current outcomes to inform decisions regarding RSV prevention.

Infant Respiratory Syncytial Virus Immunization Coverage in the Vaccine Safety Datalink: 2023-2024

BACKGROUND AND OBJECTIVES

In 2023, the Advisory Committee on Immunization Practices recommended either Abrysvo, a vaccine administered during pregnancy, or nirsevimab, a monoclonal antibody administered to infants after birth, to protect infants from respiratory syncytial virus (RSV). Our objective was to assess the proportion of infants immunized against RSV through antenatal RSV vaccination or receipt of nirsevimab among linked pregnancy-infant dyads.

METHODS

Using data from 10 Vaccine Safety Datalink health systems and a validated algorithm, we identified pregnant women aged 12 to 55 years with a live birth of 32 weeks' gestation or more from September 22, 2023, through March 31, 2024. We identified RSV vaccination using electronic health records supplemented with immunization information system (registry) data. Among infants from eligible pregnancies, we identified nirsevimab administered through March 31, 2024. We assessed infant RSV immunization, defined as exposure to antenatal RSV vaccination or receipt of nirsevimab, stratified by race and ethnicity, age, and birth month.

RESULTS

A total of 36 949 eligible infants were included from 43 722 pregnancies. Overall, 72% of infants were immunized against RSV; estimates were highest among infants born to non-Hispanic (NH) Asian mothers (84%). Disparities were identified by race, with 60% coverage among infants born to NH Black or NH Middle Eastern or North African mothers. Coverage was 59% to 78% by birth month, with nirsevimab more commonly administered to infants born earlier in the season.

CONCLUSIONS

In this population of infants, 72% were immunized against RSV. Although overall coverage was high, disparities in immunization by race and ethnicity are a call to action.

Pregnant persons perceptions and uptake of prenatal RSV vaccine - Minnesota, 2023-2024

BACKGROUND

Respiratory syncytial virus (RSV) vaccine was recommended for use during pregnancy in September 2023.

OBJECTIVE

To assess pregnant persons' intentions to receive and evaluate factors associated with RSV vaccine intentions and uptake.

STUDY DESIGN

We invited 1999 pregnant persons ≥18 years, between 12 and 30 weeks gestation who had received prenatal care at HealthPartners to complete an online survey during September-November 2023. Our primary outcome was intention to receive RSV vaccine. We also asked respondents about reasons to or not to receive RSV vaccine and intentions to receive other vaccines during pregnancy. We assessed RSV vaccine uptake for patients 32-36 weeks gestation between 10/12/23 (first RSV vaccine in study population) and 2/1/24. We estimated adjusted prevalence ratios (aPR) and 95 % confidence intervals (CI) between responses and intention to receive RSV vaccination and, for those eligible to receive RSV vaccine, adjusted rate ratios (aRR) and 95 % CIs for RSV vaccine uptake. We adjusted aPRs and aRRs for age, race, ethnicity, Medicaid, living with children ≤5 years, and work in healthcare and weighted by inverse probability of survey participation using Poisson regression with robust variance.

RESULTS

455 patients participated (23 % response), 26 % were non-white and/or Hispanic, 46 % lived with children ≤5 years, and 30 % work in healthcare; 65 % intended to receive RSV vaccine during pregnancy. Among 427 eligible respondents, 51 % received RSV vaccine. Factors associated with RSV vaccination intention and uptake included perceived vaccine effectiveness (aPR: 19.47, 95 % CI: 5.82, 65.12; aRR 3.06, 95 % CI: 1.70, 5.51) and a provider recommendation (aPR: 8.04, 95 % CI: 4.23, 15.29; aRR 3.30, 95 % CI: 1.99, 5.48). Among those not planning to receive RSV vaccine, responses suggested safety concerns.

CONCLUSION

Strong recommendations for receiving RSV vaccine during pregnancy from a healthcare provider incorporating information about RSV vaccine safety and effectiveness may increase vaccine uptake.

Administration of Nirsevimab for RSV Prophylaxis in Infants: A Comprehensive Review

Respiratory syncytial virus (RSV) is the primary etiological agent responsible for lower respiratory tract infections (LRTIs) and hospitalizations among infants. Nirsevimab, a novel monoclonal antibody (mAb), offers sustained protection against RSV for a minimum of 5 months in neonates and young children. Extensive clinical trials and real-world evidence have demonstrated that nirsevimab significantly mitigates the incidence and severity of RSV infections in infants, while exhibiting favorable safety profiles and cost-effectiveness. Regulatory authorities in multiple countries have approved nirsevimab, and its implementation is progressively expanding across various healthcare settings. However, several critical issues require further attention. Specifically, a more in-depth investigation into the long-term efficacy and benefits of nirsevimab across diverse populations, particularly neonates, is essential. Additionally, accelerating the introduction and administration of nirsevimab in developing countries remains imperative. Thus, this review comprehensively summarizes the administration of nirsevimab in infants to facilitate its broader application.

Vaccination in pregnancy to protect the newborn

Infectious diseases pose a particular risk to newborns and there is a global need to protect this vulnerable group. Because of the challenges of developing vaccines that are effective in newborns, only the hepatitis B and tuberculosis vaccines are given in the first 28 days of life, and even those vaccines are mainly only offered to high-risk groups. Maternal antibodies cross the placenta and can afford some protection to the newborn, so an alternative strategy is vaccination in pregnancy. This approach has been successfully used to protect newborns against tetanus and pertussis, and vaccines that are primarily offered to protect the mother during pregnancy, such as influenza and COVID-19 vaccines, also provide some protection to newborns. A respiratory syncytial virus vaccine has recently been approved for use in pregnancy to protect newborns, and a new vaccine that will be offered during pregnancy to prevent Group B Streptococcus infection in infants is on the horizon. Here, we discuss the current vaccines that are offered during pregnancy and to newborns, the vaccines in development for future use in these groups and the challenges that remain concerning the delivery and uptake of such vaccines.

Maternal Immunization

Pregnant individuals and infants are at risk from vaccine-preventable diseases like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza. Maternal vaccination during pregnancy can protect both the mother and child. Recent progress in developing these vaccines is notable, but vaccine hesitancy and the exclusion of pregnant individuals from clinical trials limit their use. Maternal immunization safeguards mothers from severe illness and adverse pregnancy outcomes while providing infants with antibodies through the placenta and breast milk. Inactivated vaccines are generally effective and safe during pregnancy. Limited safety and efficacy data due to exclusion from trials hinder vaccine uptake; however, vaccines like tetanus-diphtheria-acellular pertussis (Tdap), influenza, and SARS-CoV-2 have proven effective, and are recommended vaccines during pregnancy. New vaccines for group B Streptococcus (GBS) and cytomegalovirus are in development, with the GBS vaccine being the most advanced. Combating vaccine hesitancy through strong health care provider recommendations is vital to enhance uptake and protect pregnant individuals and their infants.

The Story behind the Science: On the discovery of respiratory syncytial virus

Respiratory syncytial virus (RSV) was discovered in 1956 by the laboratory of Robert Chanock after its isolation from children with upper respiratory infections. Here, we review the events leading to its discovery including its prior isolation as chimpanzee coryza virus and its subsequent association with human disease.

RSV F evolution escapes some monoclonal antibodies but does not strongly erode neutralization by human polyclonal sera

Vaccines and monoclonal antibodies targeting the respiratory syncytial virus (RSV) fusion protein (F) have recently begun to be widely used to protect infants and high-risk adults. Some other viral proteins evolve to erode polyclonal antibody neutralization and escape individual monoclonal antibodies. However, little is known about how RSV F evolution affects antibodies. Here we develop an experimental system for measuring neutralization titers against RSV F using pseudotyped lentiviral particles. This system is easily adaptable to evaluate neutralization of relevant clinical strains. We apply this system to demonstrate that natural evolution of RSV F leads to escape from some monoclonal antibodies, but at most modestly affects neutralization by polyclonal serum antibodies. Overall, our work sheds light on RSV antigenic evolution and describes a tool to measure the ability of antibodies and sera to neutralize contemporary RSV strains.

Hospital admissions for acute respiratory tract infections among infants from Nunavut and the burden of respiratory syncytial virus: a 10-year retrospective cohort study

Background

Nunavut is a northern Canadian territory where a high proportion of infants are admitted to hospital with acute respiratory tract infection (ARI). Previous studies have been limited in regional and/or short duration of coverage. This study aimed to estimate the incidence rate, microbiology and outcomes of ARI hospitalizations in Nunavut infants.

Methods

We conducted a retrospective cohort study of infants aged <1 year from Nunavut hospitalized for ARI at two regional and four tertiary pediatric hospitals in Canada, January 1, 2010, to June 30, 2020. One regional hospital was located in Nunavut; others were located across Canada. Descriptive statistics and multivariable logistic regression were performed.

Findings

We identified 1189 ARI admissions, with an incidence rate of 133.9 per 1000 infants per year (95% confidence interval (CI): 126.8, 141.3). Of these admissions, 56.0% (n = 666) were to regional hospitals alone, 72.3% (n = 860) involved hospitalization outside of Nunavut, 15.6% (n = 185) were admitted into intensive care, and 9.2% (n = 109) underwent mechanical ventilation. Among 730 admissions with a pathogen identified, 45.8% had respiratory syncytial virus (RSV; n = 334), for a yearly incidence rate of 37.8 RSV-associated hospitalizations per 1000 infants (95% CI: 33.9, 42.1). Among RSV-associated hospitalizations, 41.1% (n = 138) were infants 0-2 months of age and 32.1% (n = 108) were >6 months. Compared with non-RSV admissions, infants with RSV had higher odds of admission into intensive care, oxygen therapy, CPAP/BiPAP respiratory support and length of hospital stay over a week.

Interpretation

Understanding the high burden of ARI among Nunavut infants can inform health policy and serve as a baseline for assessing the impact of any new interventions targeting infant ARIs.

Funding

Public Health Agency of Canada and Canadian Institutes of Health Research via the Canadian Immunization Research Network (CNF 151944).

Healthcare utilization during acute medically attended episodes of respiratory syncytial virus-related lower respiratory tract infection among infants in the United States

BACKGROUND

Respiratory syncytial virus (RSV) is the leading cause of infant hospitalization in the United States. Understanding healthcare utilization associated with medically attended (MA) RSV lower respiratory tract infection (LRTI) might inform research priorities aimed at reducing RSV-associated pediatric morbidity. We described healthcare utilization during acute MA RSV LRTI episodes within a geographically diverse cohort of infants in the United States.

METHODS

We created retrospective cohorts of infants born in the United States from July 1, 2016 through February 29, 2020 in each of three de-identified insurance claims datasets: Merative MarketScan Commercial Claims and Encounters, Multi-State MarketScan Medicaid, and Optum's de-identified Clinformatics ® Data Mart. We identified infants' first MA RSV LRTI diagnosis during their first RSV season and followed them for 7 subsequent days to record outpatient, emergency department, and inpatient hospital utilization. We calculated the number of outpatient visits, emergency department visits, and inpatient hospital stays occurring during this acute episode and estimated the proportion of episodes involving ≥ 2 visits to a given healthcare setting.

RESULTS

In the CCAE database, we identified 25,409 acute MA RSV LRTI episodes under the specific RSV definition and 69,068 under the sensitive definition. In the MDCD database, these totals were 67,357 and 170,744, while in the CDM database, they were 12,402 and 31,363, respectively. Across data sources, 34%-69% of infants' first acute MA RSV LRTI episodes involve 2 or more visits to a healthcare setting within 7 days. The percentage of episodes involving at least 2 visits ranged from 34-62% among healthy term infants, 38-65% for Palivizumab-eligible infants, and 38-69% for infants with other comorbidities.

CONCLUSIONS

Within a week of their first MA RSV LRTI diagnosis, infants frequently experience at least 2 visits to one or more healthcare settings, regardless of their comorbidity profile. The percentage of MA RSV LRTI episodes involving at least 2 visits to a healthcare setting may vary by insurance claims database, even between commercial payers.

Respiratory Syncytial Virus Vaccine and Nirsevimab Uptake Among Pregnant People and Their Neonates

Importance

Two interventions to prevent severe respiratory syncytial virus (RSV) in infants were approved in 2023-a bivalent prenatal RSV prefusion F protein-based (RSVpreF) vaccine and an infant monoclonal antibody (nirsevimab). Understanding their uptake and clinical outcomes is essential for public health planning.

Objective

To describe uptake of the prenatal RSVpreF vaccine and infant nirsevimab.

Design, Setting, and Participants

This retrospective cohort study was conducted at a single academic center among 647 pregnant individuals eligible for RSVpreF vaccination (32-36 weeks' gestation between October 15, 2023, and January 31, 2024) and infants eligible for nirsevimab (no prenatal RSVpreF vaccination >14 days before delivery).

Exposure

Pregnancy or birth during the 2023-2024 RSV season.

Main Outcomes and Measures

RSVpreF vaccination among eligible pregnant individuals and nirsevimab administration prior to hospital discharge among eligible infants.

Results

Of 647 eligible pregnant individuals (mean [SD] age, 34.6 [6.2] years; 355 nulliparous [54.9%]; 558 privately insured [86.2%]), 414 (64.0%) received the RSVpreF vaccine. Factors associated with higher RSVpreF uptake included older birthing parent age (adjusted odds ratio [AOR], 1.09; 95% CI, 1.05-1.12), nulliparity (AOR, 1.84; 95% CI, 1.31-2.60), private insurance (AOR, 2.19; 95% CI, 1.27-3.80), non-Hispanic ethnicity (AOR, 2.36; 95% CI 1.57-3.55; reference: Hispanic), receipt of any COVID-19 vaccine (AOR, 7.12; 95% CI, 3.91-13.70), 2023-2024 formula COVID-19 booster vaccine (AOR, 5.62; 95% CI, 3.80-8.48), influenza vaccine (AOR, 8.14; 95% CI, 5.38-12.50), or tetanus-diphtheria-pertussis vaccine (AOR, 6.86; 95% CI, 3.79-13.10). Factors associated with lower RSVpreF uptake included non-English language preference (AOR, 0.24; 95% CI, 0.10-0.52), Black race (AOR, 0.30; 95% CI, 0.16-0.57; reference: Asian), other or unknown race (AOR, 0.48; 95% CI, 0.30-0.76), and multiple gestation (AOR, 0.27; 95% CI, 0.07-0.88). Nirsevimab was administered to 183 of 261 eligible infants (70.1%) prior to hospital discharge. Among those who did not receive RSVpreF or standard prenatal vaccines, 40.4% of their neonates (19 of 47) received nirsevimab; among those who declined infant hepatitis B vaccination, 34.0% of their neonates (17 of 50) received nirsevimab. Respiratory syncytial virus coverage exceeded 80% during all months of the study period except October 2023, the first month during which prenatal RSV vaccination and infant nirsevimab were available. Preterm delivery occurred in 35 of 414 RSVpreF-vaccinated individuals (8.5%) and 43 of 233 unvaccinated individuals (18.5%). In a nested case-control analysis with preterm birth as the outcome, there was no significant association between RSVpreF vaccination and preterm birth (AOR, 1.03; 95% CI, 0.55-1.93).

Conclusions and Relevance

In this cohort study, uptake of the RSVpreF vaccine and infant nirsevimab was high. Nirsevimab uptake was high even among individuals who did not receive routine prenatal or infant vaccines. There was no significant association between RSVpreF vaccination and preterm birth. This study suggests that an RSV prevention strategy that included both prenatal vaccination and infant monoclonal antibody administration had high uptake and reassuring perinatal outcomes.

Incidence of and Risk Factors for Subsequent Lower Respiratory Tract Infection Following an Infant RSV Hospitalization

Background/Objectives: Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis and pneumonia in infants and the leading cause of infant hospitalization in the U.S. and worldwide. The risk of experiencing at least one other medically attended lower respiratory tract infection (MA LRTI) following an infant RSV hospitalization is less studied. Methods: We conducted a retrospective cohort study of infants who experienced an RSV hospitalization (index hospitalization) during infancy. The incidence rate of having a subsequent MA LRTI was reported. The association between a priori selected maternal and infant risk factors and subsequent MA LRTI was determined. Results: Of the 20,181 children who experienced an RSV hospitalization in infancy, 15% had at least one subsequent MA LRTI within the same RSV season. The incidence rates (95% confidence interval) of having a subsequent MA LRTI hospitalization, emergency department visit, or physician office visit in the same RSV season were 0.27 (0.26, 0.29), 0.16 (0.15, 0.17), and 0.46 (0.44, 0.48) per infant-year, respectively. Factors associated with an increased risk of subsequent MA-LRTI include younger maternal age, fewer years of maternal education, smoking during pregnancy, cesarean delivery, male infant sex, White race, siblings at home, urban residence, lower birth weight, lower gestational age, eligibility for and/or ever receiving palivizumab, longer birth hospitalization length of stay, longer index RSV hospitalization length of stay, intensive care unit admission for the index hospitalization, and summer-to-fall births. Conclusions: The burden of clinically significant subsequent MA-LRTI following an RSV hospitalization can be substantial. Our results highlight the importance of increasing accessible RSV LRTI preventive interventions.

Respiratory Syncytial Virus Disease Burden and Nirsevimab Effectiveness in Young Children From 2023-2024

Importance

During the 2023-2024 respiratory syncytial virus (RSV) season in the United States, 2 new RSV prevention products were recommended to protect infants in their first RSV season: nirsevimab and Pfizer's maternal RSV vaccine. Postlicensure studies are needed to assess prevention product impact and effectiveness.

Objective

To compare the epidemiology and disease burden of medically attended RSV-associated acute respiratory illness (ARI) among children younger than 5 years during the 2023-2024 RSV season with 3 prepandemic RSV seasons (2017-2020), estimate nirsevimab effectiveness against medically attended RSV-associated ARI, and compare nirsevimab binding site mutations among circulating RSV in infants with and without nirsevimab receipt.

Design, Setting, and Participants

This study included prospective population-based surveillance for medically attended ARI with systematic molecular testing for RSV and whole-genome sequencing of RSV positive samples, as well as a test-negative case-control design to estimate nirsevimab effectiveness. The study was conducted in 7 academic pediatric medical centers in the United States with data from RSV seasons (September 1 through April 30) in 2017 through 2020. Participants were children younger than 5 years with medically attended ARI.

Exposure

For the nirsevimab effectiveness analyses, nirsevimab receipt among infants younger than 8 months as of or born after October 1, 2023.

Main Outcome and Measure

Medically attended RSV-associated ARI.

Results

Overall, 28 689 children younger than 5 years with medically attended ARI were enrolled, including 9536 during September 1, 2023, through April 30, 2024, and 19 153 during the same calendar period of 2017-2020. Of these children, 16 196 (57%) were male, and 12 444 (43.4) were female; the median (IQR) age was 15 (6-29) months. During 2023-2024, the proportion of children with RSV was 23% (2199/9490) among all medically attended episodes, similar to 2017-2020. RSV-associated hospitalization rates in 2023-2024 were similar to average 2017-2020 seasonal rates with 5.0 (95% CI, 4.6-5.3) per 1000 among children younger than 5 years; the highest rates were among children aged 0 to 2 months (26.6; 95% CI, 23.0-30.2). Low maternal RSV vaccine uptake precluded assessment of effectiveness. Overall, 10 of 765 case patients (1%) who were RSV positive and 126 of 851 control patients (15%) who were RSV negative received nirsevimab. Nirsevimab effectiveness was 89% (95% CI, 79%-94%) against medically attended RSV-associated ARI and 93% (95% CI, 82%-97%) against RSV-associated hospitalization. Among 229 sequenced specimens, there were no differences in nirsevimab binding site mutations by infant nirsevimab receipt status.

Conclusions and Relevance

This analysis documented the continued high burden of medically attended RSV-associated ARI among young children in the US. There is a potential for substantial public health impact with increased and equitable prevention product coverage in future seasons.

A framework for monitoring RSV prevention product effectiveness in the United States

During 2023, the Centers for Disease Control and Prevention (CDC) recommended the first respiratory syncytial virus (RSV) immunizations intended for widespread use in the United States to prevent severe RSV illness in infants and older adults. CDC, in collaboration with federal, public health, and academic partners, is conducting evaluations of real-world effectiveness of recommended RSV immunization products in the United States. Similar frameworks for evaluation are being applied to RSV vaccines and nirsevimab, a long-acting preventative monoclonal antibody, to estimate product effectiveness. The overall goal of CDC's RSV immunization effectiveness program is to generate timely and robust evidence through observational studies to inform immunization product policy decisions and other measures related to RSV prevention and control. CDC is evaluating effectiveness through high-quality, well-controlled observational studies leveraging a variety of platforms that provide robust data to inform policy decisions.

Inpatient service utilization amongst infants diagnosed with Respiratory Syncytial Virus infection (RSV) in the United States

INTRODUCTION

Respiratory syncytial virus (RSV) is the leading cause of hospitalization among US infants. Characterizing service utilization during infant RSV hospitalizations may provide important information for prioritizing resources and interventions.

OBJECTIVE

The objective of this study was to describe the procedures and services received by infants hospitalized during their first RSV episode in their first RSV season, in addition to what proportion of infants died during this hospitalization.

METHODS

In this retrospective observational study, we analyzed three different administrative claims datasets to examine healthcare service utilization during RSV hospitalizations among infants. The study population included infants born between July 2016 and February 2020 who experienced an RSV episode during their first RSV season and had an associated inpatient hospitalization. We stratified infants into three comorbidity groups: healthy term, palivizumab-eligible, and other comorbidities. Outcomes included extracorporeal membrane oxygenation, supplemental oxygen use (in-hospital and post-discharge), mechanical ventilation (invasive and non-invasive), chest imaging, infant mortality, length of inpatient stay, intensive care unit (ICU) admission, and number of days in the ICU.

RESULTS

Chest imaging was the most frequently administered procedure during RSV-associated hospitalizations, with approximately 34-38% of infants receiving it. Around one-quarter of infants were admitted to the ICU during their first RSV hospitalization. Median lengths of stay in the hospital were 3-4 days, extending to 4-6 days in the presence of ICU admission. Palivizumab-eligible infants had higher utilization of healthcare services and spent more time in the hospital or ICU compared to healthy infants or those with other comorbidities.

CONCLUSIONS

This study provides insights into the utilization of healthcare services during RSV hospitalizations among infants. Understanding service utilization patterns can aid in improved management and resource allocation for infants in the United States, ultimately contributing to better outcomes and reduced healthcare costs overall. However, likely under-ascertainment of ventilation and oxygen-related services in insurance claims remains an impediment to studying these outcomes.

Practical Application of Nirsevimab Recommendations for Infants and Toddlers

Respiratory syncytial virus (RSV) is a common respiratory tract infection that causes bronchiolitis and pneumonia in infants and children. It is the leading cause of hospitalization of infants in the United States. Nirsevimab is a long-acting monoclonal antibody recommended for the prevention of severe disease in all infants under 8 months of age and certain high-risk toddlers. Recent data demonstrate a 90% protection against hospitalization from severe RSV disease for infants who received nirsevimab in their first RSV season. Providers should understand the mechanism of action, safety, efficacy, and prescribing recommendations for nirsevimab, especially when confronted with caregivers who are hesitant about medications and vaccines. Special circumstances may require nuanced prescribing of nirsevimab to safely provide optimal protection. In these circumstances, and during drug shortages, a lens of health equity should be used to protect the highest risk populations.

Infant-derived human nasal organoids exhibit relatively increased susceptibility, epithelial responses, and cytotoxicity during RSV infection

BACKGROUND

Respiratory syncytial virus (RSV) causes significant morbidity and mortality, especially in young children. Why RSV infection in children is more severe compared to healthy adults is not fully understood.

METHODS

We used ex-vivo human nasal organoid platforms from infants and adults to investigate the underlying mechanism of this disease disparity at the initial site of RSV replication, the nasal epithelium.

RESULTS

Infant-derived human nasal organoid-air liquid interface (HNO-ALIs) lines were more susceptible to early RSV replication. Moreover, infant-derived HNO-ALIs elicited a statistically significant greater overall cytokine response, enhanced mucous production, and greater cellular damage compared to their adult counterparts. Furthermore, the adult cytokine response was associated with a superior regulatory cytokine response, which could explain less cellular damage than in infant lines.

CONCLUSIONS

Our data highlights substantial differences in how infant and adult upper respiratory tract epithelium responds to RSV infection at the cellular level. These differences in epithelial cellular response can lead to impaired mucociliary clearance, a more dysregulated innate immune response predisposing infants to more severe RSV infection compared to adults.

Comparison of mortality and cardiovascular complications due to COVID-19, RSV, and influenza in hospitalized children and young adults

BACKGROUND

Respiratory viruses are linked to cardiovascular complications. We aim to compare cardiovascular complications due to COVID-19, influenza and RSV.

METHODS

We analyzed cross-sectional data from hospitalized children and young adults (≤ 20 years) from 2020 and 2021 using National Inpatient Sample (NIS). We included individuals hospitalized for COVID-19, RSV, and influenza, and weighted data were used to compare cardiovascular complications.

RESULTS

Of 212,655 respiratory virus admissions, 85,055 were from COVID-19, 103,185 were from RSV, and 24,415 were from influenza. Myocarditis was higher in COVID-19 [0.9%, n = 740] as compared to influenza [0.2%, n = 55] and RSV [0.1%, n = 65]. In the adjusted logistic regression, the odds of myocarditis was 61% lower in influenza [aOR = 0.39 (0.20-0.76), P = 0.006], and 85% lower in RSV [aOR = 0.15 (0.07-0.34) P < 0.001] as compared to COVID-19. Bradyarrhythmias/heart block was higher in COVID-19 [0.8%, n = 690] versus influenza [0.5%, n = 110] and RSV [0.2%, n = 205]. After adjusting for confounders for bradyarrhythmias/heart block, compared to COVID-19, the odds were 49% lower in RSV [aOR = 0.51 (0.33-0.80), P = 0.004] but no statistically significant difference in influenza [aOR = 0.79 (0.48-1.31), P = 0.374] was seen. Tachyarrhythmias, sudden cardiac arrest, and in-hospital mortality showed no differences after adjusting for covariates.

CONCLUSION

Individuals with COVID-19 infection are more likely to develop cardiovascular complications compared to influenza and RSV, highlighting the need for higher index of suspicion and prompt treatment, as well as steps to limit infection and transmission of this virus in children.

Respiratory Syncytial Virus: A WAidid Consensus Document on New Preventive Options

Background/Objectives: Respiratory syncytial virus (RSV) is a leading cause of respiratory infections, particularly affecting young infants, older adults, and individuals with comorbidities. Methods: This document, developed as a consensus by an international group of experts affiliated with the World Association of Infectious Diseases and Immunological Disorders (WAidid), focuses on recent advancements in RSV prevention, highlighting the introduction of monoclonal antibodies (mAbs) and vaccines. Results: Historically, RSV treatment options were limited to supportive care and the monoclonal antibody palivizumab, which required multiple doses. Recent innovations have led to the development of long-acting mAbs, such as nirsevimab, which provide season-long protection with a single dose. Nirsevimab has shown high efficacy in preventing severe RSV-related lower respiratory tract infections (LRTIs) in infants, reducing hospitalizations and ICU admissions. Additionally, new vaccines, such as RSVpreF and RSVpreF3, target older adults and have demonstrated significant efficacy in preventing LRTIs in clinical trials. Maternal vaccination strategies also show promise in providing passive immunity to newborns, protecting them during the most vulnerable early months of life. This document further discusses the global burden of RSV, its economic impact, and the challenges of implementing these preventative strategies in different healthcare settings. Conclusions: The evidence supports the integration of both passive (mAbs) and active (vaccines) immunization approaches as effective tools to mitigate the public health impact of RSV. The combined use of these interventions could substantially reduce RSV-related morbidity and mortality across various age groups and populations, emphasizing the importance of widespread immunization efforts.

Respiratory syncytial virus burden in children under 2 years old in understudied areas worldwide: gap analysis of available evidence, 2012-2022

Background

We evaluated published evidence (2012-2022) on pediatric RSV burden in 149 countries within World Health Organization (WHO) regions of Africa (AFRO), Americas (AMRO, excluding Canada and the USA), Eastern Mediterranean (EMRO), Europe (EURO, excluding European Union countries and the UK), Southeast Asia (SEARO), and Western Pacific (WPRO, excluding Australia, China, Japan, New Zealand, and South Korea).

Methods

Gap analysis on RSV-associated disease (hospitalizations, hospital course, mortality or case fatality, detection, and incidence) in children ≤2 years old, where hospitalization rates, hospital course, mortality rate, case fatality rate (CFR), and postmortem detection rates were summarized, by region, for each country.

Results

Forty-two publications were identified covering 19% of included countries in AFRO, 18% in AMRO, 14% in EMRO, 15% in EURO, 18% in SEARO, and 13% in WPRO. Methods, case definitions, and age groups varied widely across studies. Of these 42 publications, 25 countries reported hospitalization rate, hospital course, mortality rate, CFR, and/or postmortem detection rate. RSV hospitalization rate (per 1,000 children per year/child-years) was higher among ≤3-month-olds (range, 38 in Nicaragua to 138 in the Philippines) and ≤6-month-olds (range, 2.6 in Singapore to 70 in South Africa) than in 1-2-year-olds (from 0.7 in Guatemala to 19 in Nicaragua). Based on 11 studies, in AFRO (South Africa), AMRO (Chile and Mexico), EMRO (Lebanon and Jordan), EURO (Israel and Turkey), and SEARO (India), hospitalized children ≤2 years old remained hospitalized for 3-8 days, with 9%-30% requiring intensive care and 4%-26% needing mechanical ventilation. Based on a study in India, community-based CFR was considerably higher than that in the hospital (9.1% vs. 0% in ≤3-month-olds; 7.1% vs. 2.8% in ≤6-month-olds).

Conclusions

National and regional heterogeneity of evidence limits estimates of RSV burden in ≤2-year-olds in many WHO region countries, where further country-specific epidemiology is needed to guide prioritization, implementation, and impact assessment of RSV prevention strategies.

SHEA practice update: infection prevention and control (IPC) in residential facilities for pediatric patients and their families

In 2011, the Society for Healthcare Epidemiology of America (SHEA) and Ronald McDonald House Charities® (RMHC®) established a formal collaboration to develop the first IPC guideline. Both organizations agreed that RMH programs staff and other organizations operating similar programs would benefit from a standardized approach. In 2023, the collaboration was re-established to revise and update the original IPC guideline. This SHEA Practice Update on "Infection Prevention and Control (IPC) in Residential Facilities for Pediatric Patients and Their Families" addresses preventing transmission of infectious agents in "home away from home" residential settings, of which the Ronald McDonald Houses (RMHs) serve as a prototype.

Regulatory review of benefits and risks of preventing infant RSV disease through maternal immunization

In August 2023, FDA approved Abrysvo for active immunization of pregnant individuals at 32 through 36 weeks gestational age to prevent lower respiratory tract disease (LRTD), including severe LRTD, caused by respiratory syncytial virus (RSV) in infants from birth through 6 months of age. A pragmatic approach to narrow the interval of use of Abrysvo in pregnant individuals balanced benefits of vaccine effectiveness against potential risks to infant and mother.

Respiratory syncytial virus disease burden in children and adults from Latin America: a systematic review and meta-analysis

Background

Respiratory Syncytial Virus (RSV) is a common cause of lower respiratory tract infections (LRTI) and hospitalization worldwide. The impact of RSV in Latin America and the Caribbean (LAC) including expensive treatment options, such as palivizumab, have been extensively discussed. However, publications on the impact of RSV disease burden in the region are scarce. This systematic review aimed to determine the incidence and prevalence of RSV in LAC by age and RSV subtype.

Methods

We conducted a systematic review following Cochrane methods to evaluate the disease burden of RSV in LAC countries. We searched studies from January 2012 to January 2023 in literature databases and grey literature without language restrictions. We included guidelines, observational, economic, and surveillance studies from LAC countries. Pairs of reviewers independently selected, and extracted data from included studies. The risk of bias was assessed using the Study Quality Assessment Tools (NHLBI) and AGREE-II. We performed proportion meta-analyses using methods to stabilize the variance. The protocol was registered in PROSPERO (CRD42023393731).

Results

We included 156 studies, mainly from Brazil (25%), Colombia (14.5%), and Argentina (13.8%), as well as four clinical practice guidelines. Most studies were cross-sectional (76.9%) and were classified as low risk of bias (52.6%). The majority included inpatients (85.6%), pediatric (73.7%), and normal-risk patients (67.1%). The highest pooled prevalence was estimated in patients <1 year old (58%), with type A and B prevalence of 52 and 34%, respectively. The RSV-LRTI incidence was 15/100 symptomatic infants aged <2 years old, and the ICU admission was 42%. The RSV-LRTI lethality was 0.6, 3% in patients aged <2 and 0-5 years old, respectively, and 23% among >65 years old high-risk patients. The identified guidelines lack methodological rigor and have limitations in their applicability. The seasonality was more evident in South America than in Central America and The Caribbean, with a clear gap during the pandemic.

Conclusion

This is the most exhaustive and updated body of evidence describing a significant burden of RSV in LAC, particularly at the extremes of life, and its seasonality patterns. Our findings could contribute could contribute facilitating effective prevention and treatment strategies for this significant public health problem.

Systematic review registration

PROSPERO CRD UK (registration number: CRD42023393731).

Healthcare resource utilisation and costs in infants with confirmed respiratory syncytial virus infections: a national population cohort study

BACKGROUND

Respiratory syncytial virus (RSV) is the leading cause of severe respiratory infections in infants worldwide, significantly affecting their health and contributing to the global healthcare burden. We aimed to examine healthcare resource utilisation patterns and costs for infants under one year old with confirmed RSV infection across subgroups of different gestational ages and health conditions and the cost implications of RSV infections over time, thereby demonstrating the economic burden of the disease.

METHODS

This retrospective cohort study utilised nationwide claims data from the Korea Health Insurance Review and Assessment Service for infants under one year of age with confirmed RSV infection in the first year of life from January 2017 to April 2022. The infants were stratified into three subgroups based on their gestational age and health status: unhealthy preterm, healthy preterm, and full-term infants. A descriptive analysis was conducted to estimate healthcare utilization by type of resource and costs related to the treatment of RSV.

RESULTS

Out of 93,585 RSV infections identified, 31,206 patients met the inclusion criteria; these included 963 unhealthy preterm, 1,768 healthy preterm and 28,475 full-term infants. In our study, 76.3% of the infants with confirmed RSV infection required intensive care, including hospitalisation and more critical interventions such as intensive care unit (ICU) or mechanical ventilation (MV). The total average cost of RSV management was notably higher for unhealthy preterm infants ($ 6,325; 95% confidence interval (CI): $ 5,484-7,165) than for healthy preterm ($ 1,134; 95% CI: $ 1,006 - 1,261) and full-term infants ($ 606; 95% CI: 583-630). Our findings confirmed a significant epidemiological and economic burden, with infants at greater risk-shorter gestational age and poorer health conditions. Furthermore, we observed a marked increase in the total average cost of RSV management during COVID-19, reflecting the complex interplay between RSV and pandemic-related healthcare dynamics.

CONCLUSION

Our findings provide evidence for the significant economic burden of RSV infection among infants, with considerable disparities based on gestational age and health status subgroups. However, RSV prevention policies should also recognise that healthy preterm or full-term infants who receive intensive care face a significant disease burden.

Respiratory virus infections in symptomatic and asymptomatic children upon hospital admission: new insights

Objective

Describe and compare the prevalence of symptomatic and asymptomatic or recently resolved respiratory infections in hospitalized children.

Design

Cross-sectional study.

Setting

Three hospital primary-to-quaternary care pediatric healthcare system.

Patients

People less than 22 years old who underwent admission screening for respiratory viruses using a multitarget polymerase chain reaction (PCR) panel from August 2020 through April 2022.

Methods

The symptom status of each patient was recorded by the ordering provider. The prevalence of each virus was described comparing symptomatic and asymptomatic patients. Results for each virus were stratified by age group and trends were examined over time.

Results

Of the 32,812 eligible PCR panels collected, 12,965 (39.5%), 18,651 (56.8%), and 1,196 (3.6%) were obtained from patients who were symptomatic, asymptomatic, or had missing or unknown symptom status, respectively. Symptomatic patients were much more likely to test positive for a respiratory virus (67.3% vs 27.0%). The most common viruses detected in asymptomatic patients were rhinovirus/enterovirus (18.0%), SARS-CoV-2 (3.6%), and parainfluenza viruses (2.3%). The odds ratio of testing positive when symptomatic was significantly greater than unity for all viruses but varied by virus and age group. The proportion of positive tests for each virus was dynamic and changed with intermittent epidemics, or viral "waves."

Conclusions

More than one-quarter of children without respiratory symptoms admitted to a pediatric healthcare system had PCR-detectable respiratory viruses. Children with symptoms of a respiratory infection are nevertheless much more likely to have a respiratory virus detected by PCR.

Paid Family Leave and Prevention of Acute Respiratory Infections in Young Infants

Importance

Acute respiratory tract infections are the leading cause of emergency department visits and hospitalizations in US children, with highest risks in the first 2 months after birth. Out-of-home childcare settings increase the spread of respiratory tract infections. The study team hypothesized that access to state-paid family leave could reduce acute care encounters (hospital admissions or emergency department visits) for respiratory tract infections in young infants by reducing out-of-home childcare transmissions.

Objective

To determine if the 2018 introduction of paid family leave in New York state reduced acute care encounters for respiratory tract infections in infants 8 weeks or younger.

Design, Setting, and Participants

This population-based study of acute care encounters took place in New York state and New England control states (Maine, Massachusetts, New Hampshire, Vermont) from October 2015 through February 2020. Participants included infants aged 8 weeks or younger. Controlled time series analysis using Poisson regression was used to estimate the impact of paid family leave on acute care encounters for respiratory tract infections, comparing observed counts during respiratory virus season (October through March) with those predicted in the absence of the policy. Acute care encounters for respiratory tract infections in 1-year-olds (who would not be expected to benefit as directly from the policy) were modeled as a placebo test.

Intervention

New York State Paid Family Leave policy, introduced on January 1, 2018, providing 8 weeks of paid leave for eligible parents.

Main Outcomes and Measures

Emergency department visits or hospitalizations with International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD) codes for upper or lower respiratory tract infections or associated symptoms (ie, fever, cough), excluding newborn hospitalizations. The secondary outcome was acute care encounters for respiratory syncytial virus (RSV) bronchiolitis.

Results

There were 52 943 acute care encounters for respiratory infection among infants 8 weeks or younger. There were 15 932 encounters that were hospitalizations (30%) and 33 304 of the encounters were paid for by Medicaid (63%). Encounters were 18% lower than predicted (relative percentage change = -17.9; 95% CI, -20.3 to -15.7) after the introduction of paid family leave. RSV encounters were 27.0% lower (95% CI, -30.9 to -23.5) than predicted. Similar reductions were not observed in 1-year-olds (relative percentage change = -1.5; 95% CI, -2.5 to -0.6).

Conclusions

New York state's paid family leave policy was associated with reduced acute care encounters for respiratory tract infections in young infants. These findings may be useful for informing implementation of paid family leave federally and in the states that have not enacted paid family leave policies.

Analysis of Beyfortus® (Nirsevimab) Immunization Campaign: Effectiveness, Biases, and ADE Risks in RSV Prevention

Respiratory infections with respiratory syncytial virus (RSV) account for an important part of hospital admissions for acute respiratory infections. Nirsevimab has been developed to reduce the hospital burden of RSV infections. Compared with the product previously used, it has a stronger binding capacity to RSV F protein and a high affinity for FcRn (neonatal receptor for the Fc fragment of IgG), which extends its lifespan. Nirsevimab has been shown to be highly effective in reducing hospitalization rates of RSV infections but a large or unknown number of treated subjects have been excluded in clinical and post-marketing studies. However, analysis of these studies cannot exclude that, in rare cases, nirsevimab facilitates and worsens RSV infection (or other respiratory infections). This could be attributable to antibody-dependent enhancement (ADE) which has been observed with RSV F protein antibodies in inactivated vaccine trials. This risk has been incompletely assessed in pre-clinical and clinical trials (incomplete exploration of nirsevimab effector functions and pharmacokinetics). ADE by disruption of the immune system (not studied and due to FcRn binding) could explain why there is no reduction in all-cause hospital admissions in treated age groups. Given the high price of nirsevimab, the cost-effectiveness of mass immunization campaigns may therefore be debated from an economic as well as a scientific point of view.

Role of Poly(A)-Binding Protein Cytoplasmic 1, a tRNA-Derived RNA Fragment-Bound Protein, in Respiratory Syncytial Virus Infection

Respiratory Syncytial Virus (RSV) is a significant cause of lower respiratory tract infections (LRTI) across all demographics, with increasing mortality and morbidity among high-risk groups such as infants under two years old, the elderly, and immunocompromised individuals. Although newly approved vaccines and treatments have substantially reduced RSV hospitalizations, accessibility remains limited, and response to treatment varies. This underscores the importance of comprehensive studies on host-RSV interactions. tRNA-derived RNA fragments (tRFs) are recently discovered non-coding RNAs, notable for their regulatory roles in diseases, including viral infections. Our prior work demonstrated that RSV infection induces tRFs, primarily derived from the 5'-end of a limited subset of tRNAs (tRF5), to promote RSV replication by partially targeting the mRNA of antiviral genes. This study found that tRFs could also use their bound proteins to regulate replication. Our proteomics data identified that PABPC1 (poly(A)-binding protein cytoplasmic 1) is associated with tRF5-GluCTC, an RSV-induced tRF. Western blot experimentally confirmed the presence of PABPC1 in the tRF5-GluCTC complex. In addition, tRF5-GluCTC is in the anti-PABPC1-precipitated immune complex. This study also discovered that suppressing PABPC1 with its specific siRNA increased RSV (-) genome copies without impacting viral gene transcription, but led to less infectious progeny viruses, suggesting the importance of PABPC1 in virus assembly, which was supported by its interaction with the RSV matrix protein. Additionally, PABPC1 knockdown decreased the production of the cytokines MIP-1α, MIP-1β, MCP-1, and TNF-α. This is the first observation suggesting that tRFs may regulate viral infection via their bound proteins.

Infectious Disease Updates for Primary Care

This article summarizes the situation with public health threats for primary care patients as of early 2024 and provides updates on strategies for the prevention, diagnosis, and treatment of common infections where new treatments and vaccines are available. For flu and COVID, an update on treatment is also provided-along with pearls useful for the busy primary care provider. The authors also discuss a new treatment option for drug-resistant vulvovaginal candidiasis and provide a balanced view of the increasingly popular technique of preventing bacterial sexually transmitted infections using doxycycline after condomless sex among men who have sex with men.

Factors Influencing Feeding Decisions in Children With Bronchiolitis on High-Flow Nasal Cannula

BACKGROUND AND OBJECTIVES

High-flow nasal cannula (HFNC) is used in up to 50% of children admitted with bronchiolitis. Consensus recommendations for feeding these children have not been established, and there is variability in practice. We sought to identify factors influencing feeding decisions for general care patients admitted with bronchiolitis on HFNC from a national sample of interdisciplinary care team members.

METHODS

In this qualitative study, we conducted semi-structured virtual interviews with care team members involved in making feeding decisions at 10 US hospitals from June 2022 to March 2023. Eligible participants included 1 nurse, respiratory therapist, speech language pathologist, and physician from each site. Interviews were audio-recorded, transcribed, and conducted until reaching sufficiency. Three researchers analyzed transcript data using content analysis guided by the Systems Engineering Initiative for Patient Safety 2.0 model.

RESULTS

We interviewed 29 participants, including 19 nurses, respiratory therapists, and speech language pathologists and 10 physicians. Participants identified 11 factors influencing feeding decisions related to hospital work systems and processes outlined in the Systems Engineering Initiative for Patient Safety model, including people (child and parent characteristics, care team experience), tools and technology (guideline, protocol, ordersets), organization (institutional culture, education), environment (time of day, care location), task (interventions to optimize feeding), and process (clinical assessment, feeding trial, communication).

CONCLUSIONS

Our findings suggest that feeding decisions are driven by factors related to the child, care team experience, institutional tools, and culture. These key factors may inform local improvement efforts to decrease variation in feeding children with bronchiolitis requiring HFNC.

Safety and Immunogenicity of Respiratory Syncytial Virus Prefusion Maternal Vaccine Coadministered With Diphtheria-Tetanus-Pertussis Vaccine: A Phase 2 Study

BACKGROUND

Respiratory syncytial virus (RSV) fusion protein stabilized in the prefusion conformation (RSVPreF3) was under investigation as a maternal vaccine.

METHODS

This phase 2, randomized, placebo-controlled, single-dose, multicenter study enrolled healthy, nonpregnant women, randomized 1:1:1:1:1 to 5 parallel groups studying RSVPreF3 (60 or 120 µg) coadministered with diphtheria, tetanus, and acellular pertussis vaccine (dTpa) or placebo, and dTpa coadministered with placebo. Safety and humoral immune responses were assessed. An extension phase also assessed a RSVPreF3 120 μg vaccination 12-18 months after first vaccination.

RESULTS

The safety profile of RSVPreF3 was unaffected by dose or dTpa coadministration. Solicited and unsolicited adverse events (AEs) were evenly distributed across study groups. Injection-site pain was higher following the second vaccination versus the first vaccination. Medically attended AEs were rare (<5% overall). Both RSVPreF3 dose levels (alone and with dTpa) were immunogenic, increasing levels of RSV-A neutralizing antibody ≥8-fold and anti-RSVPreF3 IgG antibody ≥11-fold at 1 month postvaccination, which persisted at 12-18 months postvaccination; modest 2-fold increases were observed with a second RSVPreF3 vaccination.

CONCLUSIONS

This study indicates RSVPreF3 coadministration with dTpa induces robust immune responses and is well tolerated, regardless of the RSVPreF3 dose level used.

CLINICAL TRIALS REGISTRATION

NCT04138056.

Nasal microRNA signatures for disease severity in infants with respiratory syncytial virus bronchiolitis: a multicentre prospective study

BACKGROUND

Respiratory syncytial virus (RSV) bronchiolitis contributes to a large morbidity and mortality burden globally. While emerging evidence suggests that airway microRNA (miRNA) is involved in the pathobiology of RSV infection, its role in the disease severity remains unclear.

METHODS

In this multicentre prospective study of infants (aged<1 year) hospitalised for RSV bronchiolitis, we sequenced the upper airway miRNA and messenger RNA (mRNA) at hospitalisation. First, we identified differentially expressed miRNAs (DEmiRNAs) associated with higher bronchiolitis severity-defined by respiratory support (eg, positive pressure ventilation, high-flow oxygen therapy) use. We also examined the biological significance of miRNAs through pathway analysis. Second, we identified differentially expressed mRNAs (DEmRNAs) associated with bronchiolitis severity. Last, we constructed miRNA-mRNA coexpression networks and determined hub mRNAs by weighted gene coexpression network analysis (WGCNA).

RESULTS

In 493 infants hospitalised with RSV bronchiolitis, 19 DEmiRNAs were associated with bronchiolitis severity (eg, miR-27a-3p, miR-26b-5p; false discovery rate<0.10). The pathway analysis using miRNA data identified 1291 bronchiolitis severity-related pathways-for example, regulation of cell adhesion mediated by integrin. Second, 1298 DEmRNAs were associated with bronchiolitis severity. Last, of these, 190 DEmRNAs were identified as targets of DEmiRNAs and negatively correlated with DEmiRNAs. By applying WGCNA to DEmRNAs, four disease modules were significantly associated with bronchiolitis severity-for example, microtubule anchoring, cell-substrate junction. The hub genes for each of these modules were also identified-for example, PCM1 for the microtubule anchoring module, LIMS1 for the cell-substrate junction module.

CONCLUSIONS

In infants hospitalised for RSV bronchiolitis, airway miRNA-mRNA coexpression network contributes to the pathobiology of bronchiolitis severity.

A Review of Respiratory Syncytial Virus Epidemiology Among Children: Linking Effective Prevention to Vulnerable Populations

Respiratory syncytial virus (RSV) is the greatest contributor to lower respiratory tract infections (LRTI) in children less than 5 years of age and the leading cause for infant hospitalizations in the United States (US). The burden of severe disease disproportionately impacts racial and ethnic minority groups, highlighting the need for interventions that promote health equity. Recent advancements in effective prophylactic agents have the potential to drastically alter the landscape of RSV disease among all young children. The effectiveness of prophylaxis, however, will rely on a clear understanding of RSV epidemiology. The purpose of this review is to discuss key aspects of RSV epidemiology while focusing on efforts to support equitable distribution of prophylactic agents to mitigate existing health disparities.

Nonadjuvanted Bivalent Respiratory Syncytial Virus Vaccination and Perinatal Outcomes

Importance

A nonadjuvanted bivalent respiratory syncytial virus (RSV) prefusion F (RSVpreF [Pfizer]) protein subunit vaccine was newly approved and recommended for pregnant individuals at 32 0/7 to 36 6/7 weeks' gestation during the 2023 to 2024 RSV season; however, clinical vaccine data are lacking.

Objective

To evaluate the association between prenatal RSV vaccination status and perinatal outcomes among patients who delivered during the vaccination season.

Design, Setting, and Participants

This retrospective observational cohort study was conducted at 2 New York City hospitals within 1 health care system among patients who gave birth to singleton gestations at 32 weeks' gestation or later from September 22, 2023, to January 31, 2024.

Exposure

Prenatal RSV vaccination with the RSVpreF vaccine captured from the health system's electronic health records.

Main Outcome and Measures

The primary outcome is preterm birth (PTB), defined as less than 37 weeks' gestation. Secondary outcomes included hypertensive disorders of pregnancy (HDP), stillbirth, small-for-gestational age birth weight, neonatal intensive care unit (NICU) admission, neonatal respiratory distress with NICU admission, neonatal jaundice or hyperbilirubinemia, neonatal hypoglycemia, and neonatal sepsis. Logistic regression models were used to estimate odds ratios (ORs), and multivariable logistic regression models and time-dependent covariate Cox regression models were performed.

Results

Of 2973 pregnant individuals (median [IQR] age, 34.9 [32.4-37.7] years), 1026 (34.5%) received prenatal RSVpreF vaccination. Fifteen patients inappropriately received the vaccine at 37 weeks' gestation or later and were included in the nonvaccinated group. During the study period, 60 patients who had evidence of prenatal vaccination (5.9%) experienced PTB vs 131 of those who did not (6.7%). Prenatal vaccination was not associated with an increased risk for PTB after adjusting for potential confounders (adjusted OR, 0.87; 95% CI, 0.62-1.20) and addressing immortal time bias (hazard ratio [HR], 0.93; 95% CI, 0.64-1.34). There were no significant differences in pregnancy and neonatal outcomes based on vaccination status in the logistic regression models, but an increased risk of HDP in the time-dependent model was seen (HR, 1.43; 95% CI, 1.16-1.77).

Conclusions and Relevance

In this cohort study of pregnant individuals who delivered at 32 weeks' gestation or later, the RSVpreF vaccine was not associated with an increased risk of PTB and perinatal outcomes. These data support the safety of prenatal RSVpreF vaccination, but further investigation into the risk of HDP is warranted.

Risk Analysis of Respiratory Syncytial Virus Among Infants in the United States by Birth Month

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of morbidity and mortality among US infants. A child's calendar birth month determines their age at first exposure(s) to RSV. We estimated birth month-specific risk of medically attended (MA) RSV lower respiratory tract infection (LRTI) among infants during their first RSV season and first year of life (FYOL).

METHODS

We analyzed infants born in the USA between July 2016 and February 2020 using three insurance claims databases (two commercial, one Medicaid). We classified infants' first MA RSV LRTI episode by the highest level of care incurred (outpatient, emergency department, or inpatient), employing specific and sensitive diagnostic coding algorithms to define index RSV diagnoses. In our main analysis, we focused on infants' first RSV season. In our secondary analysis, we compared the risk of MA RSV LRTI during infants' first RSV season to that of their FYOL.

RESULTS

Infants born from May through September generally had the highest risk of first-season MA RSV LRTI-approximately 6-10% under the specific RSV index diagnosis definition and 16-26% under the sensitive. Infants born between October and December had the highest risk of RSV-related hospitalization during their first season. The proportion of MA RSV LRTI events classified as inpatient ranged from 9% to 54% (specific) and 5% to 33% (sensitive) across birth month and comorbidity group. Through the FYOL, the overall risk of MA RSV LRTI is comparable across birth months within each claims database (6-11% under the specific definition, 17-30% under the sensitive), with additional cases progressing to care at outpatient or ED settings.

CONCLUSIONS

Our data support recent national recommendations for the use of nirsevimab in the USA. For infants born at the tail end of an RSV season who do not receive nirsevimab, a dose administered prior to the onset of their second RSV season could reduce the incidence of outpatient- and ED-related events.

Nirsevimab immunization's real-world effectiveness in preventing severe bronchiolitis: A test-negative case-control study

BACKGROUND

Several clinical trials have shown that nirsevimab, an antibody targeting the respiratory syncytial virus (RSV), reduces RSV bronchiolitis requiring admission. In 2023-2024, Catalonia and Andorra adopted immunization strategies for children <6 months and those born during the epidemic season. This study evaluates the effectiveness of nirsevimab in preventing hospitalizations from RSV bronchiolitis.

METHODS

In the epidemic season of 2023-2024, a test-negative case-control study was conducted in three hospitals from Catalonia and Andorra. Patients <12 months old admitted with bronchiolitis and tested for RSV using molecular microbiology tests were included. The effectiveness in preventing RSV bronchiolitis hospitalization and severe disease was estimated using multivariate models. Comparisons between immunized, non-immunized, and non-eligible patients were made in prospectively collected epidemiological, clinical, and microbiological variables.

RESULTS

Two hundred thirty-four patients were included. RSV was detected in 141/234 (60.2%), being less common in the immunized group (37% vs 75%, p < .001). The rate of immunized patients among those eligible was 59.7%. The estimated effectiveness for RSV-associated lower respiratory tract infection was 81.0% (95% confidence interval: 60.9-90.7), and for preventing severe disease (the need for NIV/CMV), 85.6% (41.7-96.4%). No significant differences by immunization status were observed in patients with RSV concerning viral coinfections, the need for NIV/CMV or length of hospital stay.

CONCLUSIONS

This study provides real-world evidence of the effectiveness of nirsevimab in preventing RSV-lower respiratory tract infection hospitalization and severe disease in infants during their first RSV season following a systematic immunization program. Immunized patients did not exhibit a higher rate of viral coinfections nor differences in clinical severity once admitted.

Trends in RSV testing patterns among infants presenting with bronchiolitis: Results from four United States health systems, 2015-2023

BACKGROUND

Bronchiolitis due to respiratory syncytial virus (RSV) is the leading cause of hospitalization among American infants. The overall burden of RSV among infants has been historically under-estimated due to variable testing practices, particularly in the outpatient setting. Universal masking and social distancing implemented during the coronavirus disease 2019 (COVID-19) pandemic altered RSV seasonality, however potential consequences on RSV testing practices across different healthcare settings and sociodemographic groups have not been described. Variable testing practices could also affect accurate assessment of the effects of two recently approved RSV preventative agents targeting infants.

METHODS

Utilizing real-time clinical and viral surveillance, we examined RSV testing practices among infants with bronchiolitis within four United States healthcare systems across different healthcare settings and sociodemographic groups pre- and post-COVID-19.

RESULTS

RSV testing among infants with bronchiolitis increased since 2015 within each healthcare system across all healthcare settings and sociodemographic groups, with a more dramatic increase since the COVID-19 pandemic. Outpatient testing remained disproportionately low compared to hospital-based testing, although there were no major differences in testing frequency among sociodemographic groups in either setting.

CONCLUSIONS

Although RSV testing increased among infants with bronchiolitis, relatively low outpatient testing rates remain a key barrier to accurate RSV surveillance.

The full value of immunisation against respiratory syncytial virus for infants younger than 1 year: effects beyond prevention of acute respiratory illness

Respiratory syncytial virus (RSV) is a leading cause of severe respiratory illness and death among children worldwide, particularly in children younger than 6 months and in low-income and middle-income countries. Feasible and cost-effective interventions to prevent RSV disease are not yet widely available, although two new products aimed at preventing RSV disease-long-acting monoclonal antibodies and maternal vaccines-have been licensed within the past 2 years. The primary target of these products is reduction of the substantial burden of RSV-associated acute lower respiratory tract infections (LRTI) in infants younger than 1 year. However, other important public health benefits might also accrue with the prevention of RSV-associated LRTI during the first year of life. Mounting evidence shows that preventing RSV-associated LRTI in infants younger than 1 year could prevent secondary pneumonia caused by other pathogens, reduce recurrent hospitalisations due to other respiratory diseases in later childhood, decrease all-cause infant mortality, ameliorate the burden of respiratory diseases on health-care systems, reduce inappropriate antibiotic use, and possibly improve lung health beyond infancy. We herein review current evidence and suggest approaches to better assess the magnitude of these potential secondary effects of RSV prevention, which, if proven substantial, are likely to be relevant to policy makers in many countries as they consider the use of these new products.

Geographic Progression of Infant Respiratory Syncytial Virus Associated Bronchiolitis Across the United States Before and Since the Onset of COVID-19: Results From Four Health Systems, 2015-2023

BACKGROUND

Respiratory syncytial virus (RSV) is a substantial cause of infant morbidity and mortality due to seasonal peaks of bronchiolitis across the United States. Clinical and viral surveillance plays a pivotal role in helping hospital systems prepare for expected surges in RSV bronchiolitis. Existing surveillance efforts have shown a geographic pattern of RSV positivity across the United States, with cases typically starting in the southeast and spreading north and west. Public health measures implemented due to the COVID-19 pandemic disrupted viral transmission across the nation and altered the expected seasonality of RSV. The impact of these changes on the geographic progression of infant RSV bronchiolitis across the United States has not been described.

METHODS

Here, we used clinical and viral surveillance data from four health care systems located in different regions of the United States to describe the geographic progression of infant RSV bronchiolitis across the country from 2015 to 2023.

RESULTS

Prior to widespread circulation of SARS-CoV-2, infant RSV bronchiolitis followed an established geographic pattern associated with seasonal epidemics originating in Florida and spreading north (North Carolina and New York) and later westward (Nevada). Although public health and social measures implemented during the COVID-19 pandemic disrupted the seasonality of RSV disease, infant RSV bronchiolitis epidemics progressed across the nation in a pattern identical to the prepandemic era.

CONCLUSIONS

Our findings highlight the importance of ongoing clinical and viral surveillance to optimally track the onset of RSV epidemics and allow health care systems to prepare for expected RSV bronchiolitis surges.

Epidemiology of Medically Attended Respiratory Syncytial Virus Lower Respiratory Tract Infection in Japanese Children, 2011-2017

BACKGROUND

The objective was to report critical respiratory syncytial virus (RSV)-related epidemiological and healthcare resource utilization measures among Japanese children stratified by gestational and chronological age groups.

METHODS

The JMDC (formerly the Japan Medical Data Center) was used to retrospectively identify infants with or without RSV infection (beginning between 1 February 2011 and 31 January 2016, with follow-up through 31 December 2017). The incidence of RSV medically attended lower respiratory tract infection (MALRI) was captured by flagging hospitalizations, outpatient, and emergency department/urgent care visits with an RSV diagnosis code during the season.

RESULTS

Of 113 529 infants and children identified, 17 022 (15%) had an RSV MALRI (14 590 during the season). The RSV MALRI and hospitalization rates in the first 5 months were 14.3/100 child-years (CY) and 6.0/100 CY, respectively (13.4/100 and 5.8/100 CY for full-term infants and 20/100 and 6.8/100 CY for late preterm infants, respectively). Among those with ≥1 type of MALRI event during the RSV season, >80% of children had it by 24 months of chronological age, although this observation differed by prematurity status. Sixty percent of healthcare resource utilization measures started in the outpatient setting.

CONCLUSIONS

This study emphasizes the RSV burden in young children and critically highlights the data needed to make decisions about new preventive strategies.

Observations of Respiratory Syncytial Virus (RSV) Nucleic Acids in Wastewater Solids Across the United States in the 2022-2023 Season: Relationships with RSV Infection Positivity and Hospitalization Rates

Respiratory syncytial virus (RSV) is a leading cause of respiratory illness and hospitalization, but clinical surveillance detects only a minority of cases. Wastewater surveillance could determine the onset and extent of RSV circulation in the absence of sensitive case detection, but to date, studies of RSV in wastewater are few. We measured RSV RNA concentrations in wastewater solids from 176 sites during the 2022-2023 RSV season and compared those to publicly available RSV infection positivity and hospitalization rates. Concentrations ranged from undetectable to 107 copies per gram. RSV RNA concentration aggregated at state and national levels correlated with infection positivity and hospitalization rates. RSV season onset was determined using both wastewater and clinical positivity rates using independent algorithms for 14 states where both data were available at the start of the RSV season. In 4 of 14 states, wastewater and clinical surveillance identified RSV season onset during the same week; in 3 states, wastewater onset preceded clinical onset, and in 7 states, wastewater onset occurred after clinical onset. Wastewater concentrations generally peaked in the same week as hospitalization rates but after case positivity rates peaked. Differences in onset and peaks in wastewater versus clinical data may reflect inherent differences in the surveillance approaches.

Healthcare Utilization Among Infants Covered by Medicaid and Newly Diagnosed With Respiratory Syncytial Virus

Background

Infants covered by Medicaid have higher respiratory syncytial virus (RSV) hospitalization rates than those with commercial insurance, but findings are limited to the inpatient setting. This birth cohort study describes healthcare encounters for RSV across all settings among infants covered by Medicaid and the Children's Health Insurance Program.

Methods

Medicaid claims for infants born and residing in Arizona (AZ), California (CA), Florida (FL), Michigan (MI), North Carolina (NC), New York (NY), and Texas (TX) were analyzed for first diagnosis of RSV in 2016-2018 using International Classification of Diseases, Tenth Revision codes. Encounters on the day of first diagnosis were examined by setting in 7 states and by setting and race in CA, FL, and NC.

Results

A total of 80 945 infants were diagnosed with RSV in 7 states in 2016-2018. The highest encounter rates for first RSV diagnosis were in the emergency department (ED) in 5 states (11.0-33.4 per 1000 in AZ, CA, FL, MI, and NY) and outpatient setting in 2 states (54.8 and 68.5 per 1000 in TX and NC). Significantly higher outpatient encounter rates were found in CA and NC for White infants compared to non-White infants. In NC, ED encounter rates were significantly higher for non-White infants than White infants, whereas in CA, the rates were comparable. In these 2 states, hospitalization rates were similar across groups. In FL, compared with White infants, non-White infants had significantly higher encounter rates in each setting on the day of first RSV diagnosis.

Conclusions

This is the first study to describe the burden of RSV by setting and race. Medicaid infants who are newly diagnosed with RSV have the highest burden in ED and outpatient settings.

Balanced on the Biggest Wave: Nirsevimab for Newborns

Respiratory syncytial virus (RSV) is the leading cause of hospitalization in infancy in the United States. Nearly all infants are infected by 2 years of age, with bronchiolitis requiring hospitalization often occurring in previously healthy children and long-term consequences of severe disease including delayed speech development and asthma. Incomplete passage of maternal immunity and a high degree of genetic variability within the virus contribute to morbidity and have also prevented successful neonatal vaccine development. Monoclonal antibodies reduce the risk of hospitalization from severe RSV disease, with palivizumab protecting high-risk newborns with comorbidities including chronic lung disease and congenital heart disease. Unfortunately, palivizumab is costly and requires monthly administration of up to five doses during the RSV season for optimal protection.Rapid advances in the past two decades have facilitated the identification of antibodies with broad neutralizing activity and allowed manipulation of their genetic code to extend half-life. These advances have culminated with nirsevimab, a monoclonal antibody targeting the Ø antigenic site on the RSV prefusion protein and protecting infants from severe disease for an entire 5-month season with a single dose. Four landmark randomized controlled trials, the first published in July 2020, have documented the efficacy and safety of nirsevimab in healthy late-preterm and term infants, healthy preterm infants, and high-risk preterm infants and those with congenital heart disease. Nirsevimab reduces the risk of RSV disease requiring medical attention (number needed to treat [NNT] 14-24) and hospitalization (NNT 33-63) with rare mild rash and injection site reactions. Consequently, the Centers for Disease Control and Prevention has recently recommended nirsevimab for all infants younger than 8 months of age entering or born during the RSV season and high-risk infants 8-19 months of age entering their second season. Implementing this novel therapy in this large population will require close multidisciplinary collaboration. Equitable distribution through minimizing barriers and maximizing uptake must be prioritized.

COVID-19, Influenza, and RSV in Children and Adults: A Clinical Comparative Study of 12,000 Cases

(1) Background: Respiratory virus infections, including Coronavirus disease 2019 (COVID-19), seasonal influenza (FLU), and respiratory syncytial virus (RSV) as prominent examples, can severely affect both children and adults. This study aimed to investigate the clinical characteristics of respiratory viral infections in pediatric and adult populations and to identify determinants influencing patient hospitalization. (2) Methods: This retrospective study analyzed the electronic medical records of patients admitted to a regional hospital's emergency department from 1 January 2015 to 31 December 2022, to investigate the clinical characteristics and hospitalization risk factors associated with these three viruses. (3) Results: Infants aged 1 to 11 months were most affected by COVID-19 and RSV, whereas FLU more commonly infected children aged 3 to 5 years. Key factors influencing hospitalization included age and abnormal chest X-ray findings, with higher risks observed in younger children and adults over 65. Notably, the presence of abnormal chest x-ray findings significantly increased the hospitalization risk by 1.9 times [1.5-2.4] in children and 21.4 times [2.4-189.0] in adults. (4) Conclusions: This analysis underscores the impact of COVID-19, FLU, and RSV on hospitalization risk, offering insights for managing these respiratory viral infections (RVIs). Age-related risk differences highlight the necessity for tailored strategies, improving understanding of and treatment development for RVIs.