Daily Respiratory Research Analysis
Three high-impact studies advance respiratory science and policy: a Nature Communications analysis elucidates why the influenza B/Yamagata lineage likely disappeared, with implications for vaccine composition; a Science Advances study shows urban daycare-driven contact patterns reshape RSV epidemics and inform seasonal immunization; and a large multicenter cohort in JAMA Network Open links timely, complete antenatal corticosteroids to reduced bronchopulmonary dysplasia in very preterm infants.
Summary
Three high-impact studies advance respiratory science and policy: a Nature Communications analysis elucidates why the influenza B/Yamagata lineage likely disappeared, with implications for vaccine composition; a Science Advances study shows urban daycare-driven contact patterns reshape RSV epidemics and inform seasonal immunization; and a large multicenter cohort in JAMA Network Open links timely, complete antenatal corticosteroids to reduced bronchopulmonary dysplasia in very preterm infants.
Research Themes
- Respiratory virus epidemiology and vaccine strategy
- Urban contact patterns and RSV control
- Perinatal interventions and neonatal lung outcomes
Selected Articles
1. Unraveling the mechanism behind the probable extinction of the B/Yamagata lineage of influenza B viruses.
Integrating antigenic, molecular, and epidemiologic evidence, the study explains B/Yamagata’s probable extinction via NPIs reducing transmission and limited antigenic evolution depleting susceptibles post-2017/18. Simulations indicate continued circulation would have required substantial drift or absence of NPIs, informing influenza vaccine composition and surveillance priorities.
Impact: Provides a mechanistic basis for retiring the B/Yamagata component from quadrivalent vaccines and reallocating surveillance resources, with broad implications for respiratory virus control.
Clinical Implications: Supports consideration of trivalent vaccine formulations and strengthens rationale to prioritize surveillance for antigenic drift in B/Victoria while maintaining sentinel systems to detect any re-emergence.
Key Findings
- B/Yamagata exhibited slower antigenic evolution and weaker positive selection compared to B/Victoria.
- NPIs during COVID-19 reduced transmission, and conserved antigenicity plus the 2017/18 outbreak depleted the susceptible pool.
- Simulations showed B/Yamagata would have persisted only with significant antigenic drift or without NPIs.
Methodological Strengths
- Integration of molecular, antigenic, and epidemiologic datasets with phylodynamic analysis
- Counterfactual simulation to test alternative transmission and antigenic drift scenarios
Limitations
- Potential biases in global surveillance data and under-detection during the pandemic
- Model assumptions may not capture all ecological or immunological complexities
Future Directions: Prospective global surveillance to confirm absence or detect re-emergence, and evaluation of vaccine policy outcomes after reformulation.
The COVID-19 pandemic caused an unprecedented disruption to the global circulation of influenza viruses. Among the most notable outcomes was the probable extinction of the B/Yamagata lineage of influenza B viruses, which has been rarely detected since March 2020. However, the underlying mechanism of the probable extinction is unknown. Here, we combine molecular, antigenic, and epidemiological data to explore the drivers of this phenomenon. Our analysis reveals that the probable extinction of B/Yamagata was driven by reduced transmission due to nonpharmaceutical interventions (NPIs) and a depleted susceptible population caused by conserved antigenicity and the 2017/2018 outbreak. Specifically, B/Yamagata exhibited slower antigenic evolution and alternating antigenic dominance compared to the co-circulating B/Victoria lineage, which was consistent with its weaker positive selection pressure. Simulation analysis suggests that B/Yamagata would maintain circulation if it underwent significant antigenic drift around the COVID-19 pandemic or if NPIs were not implemented. These findings provide a mechanistic explanation for the probable extinction of B/Yamagata and offer broader insights for controlling similar respiratory viruses.
2. Urban contact patterns shape respiratory syncytial virus epidemics with implications for vaccination.
County-level RSV data reveal an urban-rural gradient: urban areas have longer epidemics and higher infant burden. A mechanistic model attributes these differences to daycare utilization in under-5s and indicates that widening seasonal immunization access in both urban and rural settings can mitigate off-season epidemics.
Impact: Links real-world contact structures to RSV epidemic features and provides actionable guidance for targeting maternal/infant immunization programs.
Clinical Implications: Supports prioritizing seasonal RSV immunization in urban locales with high daycare use and ensuring equitable access in rural areas to prevent off-season surges.
Key Findings
- Urban areas experience more prolonged RSV epidemics with a higher burden in infants under 1 year.
- Daycare utilization among children <5 years explains urban–rural differences in epidemic intensity and age structure.
- Expanding seasonal immunization access across urban and rural areas reduces off-season epidemic risk in simulations.
Methodological Strengths
- Nationwide county-level analysis coupled with mechanistic modeling
- Clear linkage of age-specific contact (daycare) to epidemic metrics with policy simulations
Limitations
- Ecological inference at county-level may not capture within-county heterogeneity
- Assumptions about daycare utilization and immunity may vary by region and over time
Future Directions: Integrate immunization uptake and vaccine effectiveness data; evaluate targeted rollout strategies for RSV monoclonal antibodies and vaccines.
Urban environments may alter the landscape of disease transmission with implications for control. Yet, it is unclear whether urban-rural differences exist in the dynamics of childhood respiratory diseases, given specific mixing patterns in younger age groups. Here, we leverage county-level data on respiratory syncytial virus (RSV) from the United States to reveal an urban-rural gradient in both the intensity and age structure of the RSV epidemic, where urban locations experience more prolonged epidemics with higher burden in infants (under 1 year of age). We develop a mechanistic epidemiological model to show that these differences can be explained by daycare utilization rates in children under 5. Using our model to consider control measures, we find that expanding seasonal immunization access in urban and rural areas may limit the risk of off season RSV epidemics.
3. Antenatal Corticosteroids and Bronchopulmonary Dysplasia in Very Preterm Infants.
In 1097 very preterm infants, complete antenatal corticosteroid courses were associated with lower moderate-to-severe BPD (ARR 0.68), less severe RDS (ARR 0.67), and shorter IMV duration. Mediation analysis supports both direct and indirect pathways, underscoring the importance of timely ACS completion and coordinated postnatal respiratory care.
Impact: Large, contemporary multicenter cohort with mediation analysis clarifies how complete ACS regimens relate to neonatal lung outcomes, informing perinatal practice.
Clinical Implications: Reinforces ensuring complete, timely ACS courses in high-risk pregnancies and aligning neonatal airway/ventilation strategies to capitalize on ACS benefits.
Key Findings
- Complete ACS associated with reduced moderate-to-severe BPD (ARR 0.68; 95% CI, 0.55–0.84).
- Severe RDS reduced (ARR 0.67; 95% CI, 0.51–0.88) and IMV duration shortened (β −2.003 days).
- Mediation analysis supports both direct and indirect effects on BPD risk.
Methodological Strengths
- Prospective multicenter design with >1000 infants and adjusted regression
- Causal mediation analysis to explore direct and indirect pathways
Limitations
- Observational design limits causal inference; residual confounding possible
- Chinese tertiary centers may limit generalizability to other settings
Future Directions: Pragmatic trials to optimize ACS timing/completion and integrated perinatal respiratory pathways; external validation across diverse health systems.
IMPORTANCE: The impact of antenatal corticosteroids (ACS) on bronchopulmonary dysplasia (BPD) in very preterm infants remains controversial, with limited evidence on causal mediation pathways. OBJECTIVE: To evaluate the association between ACS and BPD in very preterm infants and assess whether respiratory distress syndrome (RDS) and invasive mechanical ventilation (IMV) have mediating roles. DESIGN, SETTING, AND PARTICIPANTS: This prospective multicenter cohort study included preterm infants from 28 tertiary centers in China between September 1, 2019, and December 31, 2020. Inclusion criteria were gestational age (GA) less than 30 weeks, admission to the neonatal intensive care unit with 24 hours of birth, and neonatal hospitalization for more than 2 weeks. Analysis was done from April 1 to May 1, 2025. EXPOSURE: Complete or incomplete ACS courses (vs no ACS). MAIN OUTCOMES AND MEASURES: The primary outcome was moderate-to-severe BPD (using National Institute of Child Health and Human Development 2001 criteria) assessed at corrected GA of 36 weeks. Secondary outcomes were severe RDS (grade 3-4) and IMV duration. Regression models adjusted for demographic, pregnancy, and birth characteristics. RESULTS: A total of 1097 preterm infants were enrolled, with median gestational age of 28.71 weeks (IQR, 27.71-29.29 weeks), median birth weight of 1150 g (IQR, 1000-1310 g), and median IMV duration of 2.0 days (IQR, 0.0-7.0 days). Of 1075 infants with available sex data, 599 (56%) were males. A total of 1069 infants had known ACS data; ACS were given in 832 cases (78%), with 518 (48%) receiving complete courses. Moderate-to-severe BPD occurred in 309 of 1097 infants (28%) and severe RDS in 237 of 1085 (22%). Complete ACS courses showed negative associations with risk of moderate-to-severe BPD (adjusted risk ratio [ARR], 0.68; 95% CI, 0.55-0.84), severe RDS (ARR, 0.67; 95% CI, 0.51-0.88), and IMV duration (β, -2.003; 95% CI, -3.391 to -0.614). Significant associations with lower BPD risk were observed in infants with GA of 28 weeks to 28 weeks 6 days (ARR, 0.47; 95% CI, 0.29-0.74), singletons (ARR, 0.67; 95% CI, 0.50-0.88), and vaginal deliveries (ARR, 0.62; 95% CI, 0.46-0.83). Mediation analysis suggested that ACS was associated with reduced risk of BPD (β, -0.050; 95% CI, -0.081 to -0.017) through direct (β, -0.031; 95% CI, -0.061 to -0.001) and indirect (β, -0.019; 95% CI, -0.032 to -0.007) effects, with the latter comprising both single and serial mediation pathways. CONCLUSIONS AND RELEVANCE: In this cohort study of preterm infants, complete ACS courses in high-risk pregnancies were associated with a reduction in neonatal BPD, potentially mediated through multifactorial pathways. Emphasizing the importance of timely ACS completion and postnatal airway management may help optimize neonatal pulmonary outcomes.