Investigating the impact of non-pharmaceutical interventions (NPIs) on post-pandemic Respiratory Syncytial Virus (RSV) hospitalisations and seasonality in Wales, UK.

Respiratory syncytial virus and palivizumab: Where are we in 2014?

The objective was to describe respiratory syncytial virus (RSV) hospitalizations in Alberta, Canada over a 13-year period with an emphasis on the incidence and risk factors for repeat hospitalizations attributable to new RSV infections. This was a retrospective database analysis. The Alberta Health Services Discharge Abstract Database was searched for patients <5 years of age admitted to any hospital with a primary diagnosis of RSV from July 1, 2004 through June 30, 2017. Clinical characteristics were compared for children with repeat RSV admission during the same RSV season (but >30 days apart so presumably due to separate infections) compared with all other children with RSV admissions. During the study period, 10 212 children had 10 967 RSV admissions. The RSV hospitalization rate was 1.6%. A total of 666 children (6.5%) were readmitted for RSV at least once during the study period, of whom 433 (4.2%) were readmitted within 30 days of the initial hospital discharge. There were 36 children (0.35%) with 2 RSV admissions >30 days apart during the same RSV season. When compared to all other children with RSV admissions, they were more likely to have congenital heart disease or to have been diagnosed with RSV pneumonia (vs bronchiolitis or upper respiratory tract infection) during their initial hospitalization. The RSV hospitalization rate in children <5 years of age was 1.6%. Repeat RSV infections requiring readmission during the same RSV season occurred following only 0.35% of RSV hospitalizations.

Respiratory syncytial virus with ongoing COVID-19: is it an emerging threat?

Risk of Childhood Asthma Following Infant Bronchiolitis During RSV Season

Respiratory syncytial virus (RSV) is a leading cause of hospitalization among young children. Historically, American Indian and Alaska Native (AI/AN) children have experienced high rates of RSV-associated hospitalization. In August 2023, a preventive monoclonal antibody (nirsevimab) was recommended for all infants aged <8 months (born during or entering their first RSV season) and for children aged 8-19 months (entering their second RSV season) who have increased risk for severe RSV illness, including all AI/AN children. This evaluation in Alaska's Yukon-Kuskokwim Delta region estimated nirsevimab effectiveness among AI/AN children in their first or second RSV seasons during 2023-2024. Among 472 children with medically attended acute respiratory illness (ARI), 48% overall had received nirsevimab ≥7 days earlier (median=91 days before the ARI-related visit). For children in their first RSV season (292), nirsevimab effectiveness was 76% (95% CI = 42%-90%) against medically attended RSV illness and 89% (95% CI = 32%-98%) against RSV hospitalization. For children in their second RSV season (180), effectiveness against medically attended RSV illness was 88% (95% CI=48%-97%). Nirsevimab is effective for preventing severe RSV illness among infants entering their first RSV season and children entering their second season with increased risk for severe RSV, including all AI/AN children.

National Immunization Technical Advisory Groups recommend long-acting monoclonal antibody prophylaxis for the prevention of respiratory syncytial virus (RSV) disease for children at high risk in the first season, regardless of RSV vaccination during pregnancy, and for those who remain at increased risk in the second season. This study assessed which groups of children with chronic medical conditions (CMCs) are at higher risk of RSV hospitalization during their first and second RSV seasons. This retrospective, population-based, season-stratified cohort analysis was conducted among children who were born between April 1, 2013, and March 31, 2023, in British Columbia, Canada (population of 5.7 million in 2024), and were enrolled in the provincial medical service plan and followed up until the day before their third RSV season or April 1, 2024, whichever occurred first. Any CMC diagnosed in the first 2 years of life. Respiratory syncytial virus-related hospitalizations. The final cohort consisted of 431 937 children (32 959 [7.6%] born at <37 weeks' gestation; 222 207 boys [51.4%]) followed up for a median of 728 days (IQR, 642-729 days), including 25 452 children (5.9%) diagnosed with at least 1 of 1116 distinct CMCs. In total, 4567 children (1.1%) experienced a combined total of 4592 RSV hospitalizations, combining data from the first and second RSV seasons. In the first RSV season, the RSV hospitalization rate per 1000 person-years for children with CMCs was 15.9 (95% CI, 14.2-17.6) and for children without CMCs was 8.0 (95% CI, 7.7-8.3). In the second RSV season, the RSV hospitalization rate per 1000 person-years for children with CMCs was 7.8 (95% CI, 6.7-8.8) and for children without CMCs was 2.2 (95% CI, 2.1-2.3). Children with multisystem CMCs, particularly those affecting the respiratory, cardiovascular, or gastrointestinal systems, had second-season RSV hospitalization rates that were at least 2-fold higher than the rate among all children in the first season. Second-season rates among children with Down syndrome or those who were born prematurely (<28 weeks of gestation) were 5-fold higher than for all children in the first season. This population-based retrospective cohort study identified specific groups of higher-risk children with CMCs who could most benefit from prophylaxis with long-acting monoclonal antibodies in their first and second RSV seasons. This study supports expanded eligibility criteria for long-acting monoclonal antibody prophylaxis.

BackgroundLittle RSV activity was observed during the first expected RSV season since the COVID‐19 pandemic. Multiple countries later experienced out‐of‐season RSV resurgences, yet their association with non‐pharmaceutical interventions (NPIs) is unclear. This study aimed to describe the changes in RSV epidemiology during the COVID‐19 pandemic and to estimate the association between individual NPIs and the RSV resurgences.MethodsRSV activity from Week (W)12‐2020 to W44‐2021 was compared with three pre‐pandemic seasons using RSV surveillance data from Brazil, Canada, Chile, France, Israel, Japan, South Africa, South Korea, Taiwan, the Netherlands and the United States. Changes in nine NPIs within 10 weeks before RSV resurgences were described. Associations between NPIs and RSV activity were assessed with linear mixed models. Adherence to NPIs was not taken into account.ResultsAverage delay of the first RSV season during the COVID‐19 pandemic was 39 weeks (range: 13–88 weeks). Although the delay was <40 weeks in six countries, a missed RSV season was observed in Brazil, Chile, Japan, Canada and South Korea. School closures, workplace closures, and stay‐at‐home requirements were most commonly downgraded before an RSV resurgence. Reopening schools and lifting stay‐at‐home requirements were associated with increases of 1.31% (p = 0.04) and 2.27% (p = 0.06) in the deviation from expected RSV activity.ConclusionThe first RSV season during the COVID‐19 pandemic was delayed in the 11 countries included. Reopening of schools was consistently associated with increased RSV activity. As NPIs were often changed concomitantly, the association between RSV activity and school closures may be partly attributed to other NPIs.

Respiratory syncytial virus (RSV) seasonality is dependent on the local climate. We assessed the stability of RSV seasonality prior to the SARS-CoV-2 pandemic in Western Australia (WA), a state spanning temperate and tropical regions. RSV laboratory testing data were collected from January 2012 to December 2019. WA was divided into three regions determined by population density and climate: Metropolitan, Northern and Southern. Season threshold was calculated per region at 1.2% annual cases, with onset the first of ≥2weeks above this threshold and offset as the last week before ≥2weeks below. The detection rate of RSV in WA was 6.3/10,000. The Northern region had the highest detection rate (15/10,000), more than 2.5 times the Metropolitan region (detection rate ratio 2.7; 95% CI, 2.6-2.9). Test percentage positive was similar in the Metropolitan (8.6%) and Southern (8.7%) regions, with the lowest in the Northern region (8.1%). RSV seasons in the Metropolitan and Southern regions occurred annually, with a single peak and had consistent timing and intensity. The Northern tropical region did not experience a distinct season. Proportion of RSV A to RSV B in the Northern region differed from the Metropolitan region in 5 of the 8years studied. Detection rate of RSV in WA is high, especially in the Northern region, where climate, an expanded at-risk population and increased testing may have contributed to greater numbers. Before the SARS-CoV-2 pandemic, RSV seasonality in WA was consistent in timing and intensity for the Metropolitan and Southern regions.

A population-based study of the impact of palivizumab on confirmed Respiratory Syncytial Virus (RSV) hospitalizations over a 7-year period within and between two similar health regions . Clinicians in Calgary implemented palivizumab prophylaxis for high-risk infants during the last four RSV seasons; clinicians in Edmonton did not. The two cities are part of a unified health care system and similar sociodemographics. Infants <36 weeks (wk) of gestational age (GA) were identified. RSV prophylaxis data and RSV-hospitalizations for high-risk infants eligible for prophylaxis were reviewed, as well as that of moderate-risk infants (33-35 weeks GA) for whom RSV prophylaxis was not given a high priority in the recommendations published by the Canadian Paediatric Society (CPS). Prevalence of RSV hospitalization before and after palivizumab was determined (1995-1998 and 1999-2002, respectively). There were 411 high-risk infants eligible for palivizumab prior to its provision (Pre) and 496 during the prophylaxis program (Post) in Calgary. There were 401 Pre and 425 Post in Edmonton, where no such prophylaxis program was implemented. In Calgary where palivizumab was offered (Post), RSV hospitalization was significantly reduced: 7.3% Pre versus 3.0% Post (OR, 2.53, 95% CI, 1.34, 4.76). No reduction was observed in Edmonton where palivizumab was not offered: 5.0% Pre versus 7.1% Post (OR, 1.45, 95% CI, 0.81, 2.59; P = 0.212). RSV hospitalizations did not change for moderate-risk infants not receiving palivizumab in Calgary (OR, 1.26, 95% CI, 0.75, 2.12; P = 0.389). An RSV prevention program with palivizumab for high-risk infants reduced RSV hospitalizations, providing "real life" evidence of the benefits of this prophylaxis strategy. Further research is required to determine if specific sub-sets of moderate-risk infants would also benefit from an RSV prophylaxis program with palivizumab.

BackgroundPreterm infants are at high risk of developing respiratory syncytial virus (RSV)-associated lower respiratory tract infection (LRTI). This observational epidemiologic study evaluated RSV disease burden and risk factors for RSV-associated LRTI hospitalization in preterm infants 33 weeks+0 days to 35 weeks+6 days gestational age not receiving RSV prophylaxis.MethodsPreterm infants ≤6 months of age during RSV season (1 October 2013–30 April 2014) were followed at 72 sites across 23 countries from September 2013–July 2014 (study period). RSV testing was performed according to local clinical practice. Factors related to RSV-associated hospitalization for LRTI were identified using multivariable logistic regression with backward selection.ResultsOf the 2390 evaluable infants, 204 and 127 were hospitalized for LRTI during the study period and RSV season, respectively. Among these subjects, 64/204 and 46/127, respectively, were hospitalized for confirmed RSV LRTI. Study period and RSV season normalized RSV hospitalization rates (per 100 infant years) were 4.1 and 6.1, respectively. Factors associated with an increased risk of RSV-related LRTI hospitalization in multivariable analyses were smoking of family members (P<0.0001), non-hemodynamically significant congenital heart disease diagnosis (P = 0.0077), maternal age of ≤25 years at delivery (P = 0.0009), low maternal educational level (P = 0.0426), household presence of children aged 4 to 5 years (P = 0.0038), age on 1 October ≤3 months (P = 0.0422), and presence of paternal atopy (P<0.0001).ConclusionsDuring the 2013–2014 RSV season across 23 countries, for preterm infants 33–35 weeks gestation ≤6 months old on 1 October not receiving RSV prophylaxis, confirmed RSV LRTI hospitalization incidence was 4.1 per 100 infant years during the study period and 6.1 per 100 infant years during the RSV season. This study enhances the findings of single-country studies of common risk factors for severe RSV infection in preterm infants and suggests that combinations of 4–6 risk factors may be used to accurately predict risk of RSV hospitalization. These findings may be useful in the identification of infants most at risk of severe RSV infection.

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. 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. 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. For the nirsevimab effectiveness analyses, nirsevimab receipt among infants younger than 8 months as of or born after October 1, 2023. Medically attended RSV-associated ARI. 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. 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.

Morbidity and health care resource utilization subsequent to respiratory syncytial virus hospitalization among infants born at 33 to 35 completed weeks gestation

* Abbreviations: LRI — : lower respiratory infection RSV — : respiratory syncytial virus SDOH — : social determinants of health During this pandemic, the impact of health disparities on mortality due to COVID-19 has been high among our concerns about this illness.1–4 Unfortunately, disparities related to respiratory infections are not limited to COVID-19. There are decades of research revealing that morbidity and mortality are strongly influenced by the social determinants of health (SDOH). Respiratory syncytial virus (RSV) is the leading cause of lower respiratory infection (LRI) in infants and a major cause of hospitalization in the first 2 years of life.5–7 In this issue of Pediatrics , Fitzpatrick et al8 report on the impact of sociodemographic and psychosocial factors on the risk for RSV hospitalization in children <3 years of age in Ontario, Canada. The authors used linked sociodemographic and health administrative data sets covering the period from 2012 to 2018 to identify factors associated with hospitalization. Their findings reveal the increased risk of hospitalization associated with maternal characteristics consistent with social vulnerability, including younger age, involvement with the criminal justice system, and mental health problems or addiction. The use of low-income drug benefits, a measure of socioeconomic status, was also associated with RSV hospitalization, as was an area level measure of income showing an increased risk of hospitalization with the lowest two quartiles of income. In their study, Fitzpatrick et al8 reinforce the important, enduring, and widespread influence of SDOH on our youngest patients. These … Address correspondence to Mary T. Caserta, MD, Department of Pediatrics, University of Rochester Medical Center, Golisano Children’s Hospital at Strong, 601 Elmwood Ave, Box 690, Rochester, NY 14642. E-mail: mary_caserta{at}urmc.rochester.edu

Respiratory syncytial virus seasonality, transmission zones, and implications for seasonal prevention strategy in China: a systematic analysis

Background The CDC currently recommends two prevention options to help protect infants against RSV-associated lower respiratory tract disease during a typical RSV season, defined as October through March. However, annual and geographic variability in RSV seasonality exists. The study evaluated the burden of RSV hospitalizations occurring outside a typical season (i.e., April – September). Methods Infants aged &amp;lt; 12 months old hospitalized with RSV were identified from the PINC AI Healthcare Database (7/1/2018 to 6/30/2023) for this descriptive cohort study. Because age is reported in years, a prior birth hospitalization record was required to determine age in months for RSV hospitalization. A surveillance year was defined by the period of July 1 of each year to June 30 of the following year. Monthly RSV hospitalizations were tallied for each of the 9 U.S. census divisions and by age group (&amp;lt; 3, 3-5, 6-8, 9-11 months). Seasonality of RSV cases among all infants &amp;lt; 1 year, regardless of the ability to identify age in months, was evaluated as a sensitivity analysis. Results A total of 56,425 RSV hospitalizations were identified among infants &amp;lt; 1 year of age, of which, 36% (n=20,531) of patients had a birth record. RSV hospitalization counts during the 5 surveillance years were 4,574 (2018/19), 4,926 (2019/20), 452 (2020/21), 4,344 (2021/22), and 6,235 (2022/23). Overall, 22% (n=4,510) of RSV hospitalizations occurred during off-season months, with 83% of these off-season cases occurring in June – September across various divisions (Fig. 1). Of all RSV hospitalizations that occurred during off-season, 45.5% (n=2,054) were among infants &amp;lt; 3 months. Seasonal patterns were similar across age groups (Fig. 2). A sensitivity analysis showed consistent seasonal patterns among all infants &amp;lt; 1 year of age. Conclusion This large-scale, real-world database analysis showed over 1 in 5 infants hospitalized with RSV were infected during off-season with varying rates by geography. The current recommendations may limit protection options for infants exposed to RSV outside the typical season. Disclosures Amy W. Law, PharmD, Pfizer Inc.: Employee|Pfizer Inc.: Stocks/Bonds (Public Company) Jay Lin, PHD, MBA, Pfizer: Advisor/Consultant Jennifer Judy, MS, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds (Public Company) Alejandro D. Cane, MD, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds (Public Company)|Pfizer: Stocks/Bonds (Public Company) Sarah J. Pugh, PhD, MPH, Pfizer Inc.: Employee|Pfizer Inc.: Stocks/Bonds (Public Company)