Daily Respiratory Research Analysis
Three studies advanced respiratory-related care and policy. A systematic review supports a single COVID-19 mRNA booster dose for individuals with prior infection ahead of respiratory seasons. Large U.S. outpatient data show markedly higher antimicrobial resistance in patients with cancer, while a competing-risk cohort study quantifies the mortality burden of nosocomial superinfections in critically ill COVID-19 patients.
Summary
Three studies advanced respiratory-related care and policy. A systematic review supports a single COVID-19 mRNA booster dose for individuals with prior infection ahead of respiratory seasons. Large U.S. outpatient data show markedly higher antimicrobial resistance in patients with cancer, while a competing-risk cohort study quantifies the mortality burden of nosocomial superinfections in critically ill COVID-19 patients.
Research Themes
- Hybrid immunity and single-dose COVID-19 booster policy
- Outpatient antimicrobial resistance burden in cancer care
- Competing-risk quantification of ICU superinfections in COVID-19
Selected Articles
1. Effectiveness of a single COVID-19 mRNA vaccine dose in individuals with prior SARS-CoV-2 infection: a systematic review.
Across 18 studies, a single mRNA dose after prior SARS-CoV-2 infection provided substantial added protection against infection, symptomatic disease, and hospitalization during Omicron waves. Protection after one dose in previously infected individuals was comparable to two doses and exceeded two-dose protection in infection-naïve individuals, supporting current single-dose recommendations ahead of respiratory seasons.
Impact: This synthesis informs vaccine policy in a high-immunity context by quantifying incremental benefits of a single booster after infection. It addresses hybrid immunity pragmatically where updated boosters are given seasonally.
Clinical Implications: For immunocompetent individuals ≥5 years with prior infection, a single mRNA dose ahead of respiratory season is reasonable, while tailoring additional doses for older adults, immunocompromised patients, and young children remains necessary.
Key Findings
- Single mRNA dose after prior infection increased protection by 8–71% against infection, 39–67% against symptomatic infection, and 25–60% against hospitalization during Omicron periods.
- One dose in previously infected individuals offered protection comparable to two doses and higher than two doses in infection-naïve individuals.
- Evidence gaps: no bivalent/XBB.1.5-adapted VE estimates, and no data for immunocompromised populations or children <5 years.
Methodological Strengths
- PROSPERO-registered systematic review with predefined methods and bias assessment (Newcastle-Ottawa Scale).
- Use of Synthesis Without Meta-Analysis guidelines to transparently summarize heterogeneous VE results.
Limitations
- No meta-analysis; heterogeneity in study designs, populations, variants, and outcomes.
- Lack of data for bivalent/XBB.1.5-adapted vaccines, immunocompromised patients, and children <5 years.
Future Directions: Quantify VE of updated XBB.1.5-adapted formulations, include immunocompromised and pediatric cohorts, assess durability of single-dose protection, and evaluate variant-specific effectiveness.
2. Incidence and prevalence of antimicrobial resistance in outpatients with cancer: a multicentre, retrospective, cohort study.
In a multicentre U.S. outpatient cohort (1,655,594 isolates), antimicrobial resistance was consistently higher among patients with cancer across key pathogens, including carbapenem-non-susceptible Pseudomonas, fluoroquinolone-non-susceptible and ESBL-producing Enterobacterales, MRSA, and VRE. Incidence rate ratios were up to threefold higher, underscoring the need for intensified surveillance and stewardship in oncology outpatients.
Impact: The scale and breadth of outpatient data reveal a substantial and actionable AMR burden in oncology, including respiratory isolates, informing empirical therapy and infection prevention beyond inpatient settings.
Clinical Implications: Empiric antibiotic choices for oncology outpatients should reflect higher AMR risks (e.g., ESBL, VRE, resistant Pseudomonas), with strengthened diagnostic stewardship and local antibiograms informing respiratory and other infections.
Key Findings
- Carbapenem non-susceptible P. aeruginosa was higher in cancer outpatients: 14.4% vs 11.3% (OR 1.22).
- Enterobacterales showed higher resistance in cancer outpatients: fluoroquinolone non-susceptibility 28.0% vs 21.8% (OR 1.44); carbapenem non-susceptibility 1.5% vs 0.8% (OR 1.89); ESBL producers 16.5% vs 9.4% (OR 1.96); multidrug resistance 8.7% vs 4.5% (OR 2.03).
- MRSA in S. aureus (53.0% vs 48.3%; OR 1.20) and VRE in Enterococcus spp (18.6% vs 9.1%; OR 2.20) were higher; IRRs up to ~3 for VRE and ~2 for carbapenem-resistant Pseudomonas.
Methodological Strengths
- Very large, multicentre dataset across 198 outpatient settings with standardized susceptibility testing.
- Pathogen- and source-specific analyses with odds ratios and incidence rate ratios.
Limitations
- Retrospective design with potential residual confounding and misclassification of cancer status.
- Lack of patient-level demographics (e.g., sex, race/ethnicity) limits risk stratification; outpatient-only data may not generalize to inpatient populations.
Future Directions: Prospective stewardship interventions in oncology outpatients, integration of molecular resistance mechanisms, and stratified analyses by infection source (including respiratory) to guide targeted empiric therapy.
3. The burden of nosocomial superinfections in a retrospective cohort study of critically ill COVID-19 patients.
Using multi-state competing-risk models in 268 critically ill COVID-19 patients, bacterial respiratory or bloodstream superinfections increased mortality (adjusted cause-specific HR 1.7) and reduced discharge rates (HR 0.51). Pathogens were predominantly Enterobacterales and nonfermenters, emphasizing early microbiologic sampling and targeted prevention.
Impact: By correctly modeling discharge and death as competing risks, this study provides robust estimates of the mortality burden attributable to superinfections in COVID-19 ICU care, informing surveillance and stewardship.
Clinical Implications: Implement systematic microbiological sampling for deteriorating ICU COVID-19 patients, prioritize prevention of Enterobacterales and nonfermenter infections, and consider competing-risk-aware metrics when benchmarking ICU infection outcomes.
Key Findings
- Bacterial respiratory or bloodstream superinfection increased mortality (adjusted cause-specific HR 1.7, 95% CI 1.15–2.52) and reduced discharge rate (HR 0.51, 95% CI 0.36–0.73).
- Predominant pathogens were Enterobacterales, nonfermenters, and Staphylococcus aureus.
- Females tended toward lower acquisition risk (adj. subdistribution HR 0.71) but showed a trend toward higher mortality once infected (interaction HR 1.49; wide CI).
Methodological Strengths
- Multi-state competing-risk modeling accounted for discharge and death, reducing bias in effect estimates.
- Prospective event capture framework with registry registration (DRKS00031367).
Limitations
- Single-country, retrospective design with potential ascertainment and treatment-confounding biases.
- Modest sample size limits precision of subgroup effects (e.g., sex interactions).
Future Directions: Prospective multicentre validation using standardized sampling protocols, stewardship interventions targeting Enterobacterales/nonfermenters, and exploration of sex-specific risks and immunologic mechanisms.