Determining the outcomes of interventions to prevent respiratory syncytial virus disease in children: what to measure?

Real-world effectiveness of nirsevimab immunisation against bronchiolitis in infants: a case-control study in Paris, France

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants. Nirsevimab, an RSV-neutralising monoclonal antibody, was approved for use in the EU in 2022, and a national immunisation campaign began in France in September, 2023. We aimed to assess the effectiveness of nirsevimab in reducing paediatric emergency department visits (and subsequent hospitalisations) for all-cause bronchiolitis and RSV-associated bronchiolitis.

METHODS

In this case-control study in a paediatric emergency department in Paris, France, we included all infants aged 12 months or younger who attended the department between Oct 14, 2023, and Feb 29, 2024, and whose nirsevimab status was known. Infants were classed as cases if they had all-cause bronchiolitis; all other infants were classed as controls. The primary outcome was the effectiveness of nirsevimab against paediatric emergency department visits for all-cause bronchiolitis during the 2023-24 RSV season. Secondary outcomes were paediatric emergency department visits for RSV-associated bronchiolitis; hospitalisations for all-cause bronchiolitis, RSV-associated bronchiolitis, and severe RSV-associated bronchiolitis requiring supplemental oxygen or feeding by nasogastric tube; and severe RSV-associated bronchiolitis requiring admission to the paediatric intensive care unit. Effectiveness estimates were adjusted for age, week of paediatric emergency department visit, and sex.

FINDINGS

Our study included 2786 infants, 864 with all-cause bronchiolitis (cases) and 1922 without bronchiolitis (controls). 178 (21%) of the 864 cases had received nirsevimab, and 305 (35%) cases were hospitalised for all-cause bronchiolitis. 200 (72%) of the 277 cases tested for RSV were positive, of whom 22 (11%) had received nirsevimab. 701 (36%) of 1922 infants in the control group had received nirsevimab. The effectiveness of nirsevimab against paediatric emergency department visits for all-cause bronchiolitis was 47% (95% CI 33-58). Nirsevimab effectiveness was 83% (71-90) against paediatric emergency department visits for RSV-associated bronchiolitis, 59% (42-71) against hospitalisations for all-cause bronchiolitis, 83% (72-90) against hospitalisations for RSV-associated bronchiolitis (91% [78-96] against those necessitating supplement oxygen and 88% [74-95] against those necessitating feeding via a nasogastric tube). Nirsevimab did not significantly reduce admissions to the paediatric intensive care unit (67% [95% CI -100 to 95]).

INTERPRETATION

During the first French national immunisation campaign, a single dose of nirsevimab effectively reduced paediatric emergency department visits (both all-cause visits and visits related to RSV-associated bronchiolitis) and subsequent hospitalisations.

FUNDING

None.

Severe respiratory syncytial virus infection in children: burden, management, and emerging therapies

The global burden of respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) in young children is high. The RSV prevention strategies approved in 2023 will be essential to lowering the global disease burden. In this Series paper, we describe clinical presentation, burden of disease, hospital management, emerging therapies, and targeted prevention focusing on developments and groundbreaking publications for RSV. We conducted a systematic search for literature published in the past 15 years and used a non-systematic approach to analyse the results, prioritising important papers and the most recent reviews per subtopic. Annually, 33 million episodes of RSV LRTI occur in children younger than 5 years, resulting in 3·6 million hospitalisations and 118 200 deaths. RSV LRTI is a clinical diagnosis but a clinical case definition and universal clinical tool to predict severe disease are non-existent. The advent of molecular point-of-care testing allows rapid and accurate confirmation of RSV infection and could reduce antibiotic use. There is no evidence-based treatment of RSV, only supportive care. Despite widespread use, evidence for high-flow nasal cannula (HFNC) therapy is insufficient and increased paediatric intensive care admissions and intubation indicate the need to remove HFNC therapy from standard care. RSV is now a vaccine-preventable disease in young children with a market-approved long-acting monoclonal antibody and a maternal vaccine targeting the RSV prefusion protein. To have a high impact on life-threatening RSV infection, infants at high risk, especially in low-income and middle-income countries, should be prioritised as an interim strategy towards universal immunisation. The implementation of RSV preventive strategies will clarify the full burden of RSV infection. Vaccine probe studies can address existing knowledge gaps including the effect of RSV prevention on transmission dynamics, antibiotic misuse, the respiratory microbiome composition, and long-term sequalae.

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.

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.

The burden of lower respiratory infections and their underlying etiologies in the Middle East and North Africa region, 1990-2019: results from the Global Burden of Disease Study 2019

BACKGROUND

Lower respiratory infections (LRIs) cause substantial mortality and morbidity. The present study reported and analysed the burden of LRIs in the Middle East and North Africa (MENA) region between 1990 and 2019, by age, sex, etiology, and socio-demographic index (SDI).

METHODS

The data used in this study were sourced from the Global Burden of Disease (GBD) study 2019. The annual incidence, deaths, and disability-adjusted life-years (DALYs) due to LRIs were presented as counts and age-standardised rates per 100,000 population, along with their 95% uncertainty intervals (UIs). The average annual percent changes (AAPC) in the age-standardised incidence, death and DALYs rates were calculated using Joinpoint software and correlations (Pearson's correlation coefficient) between the AAPCs and SDIs were calculated using Stata software.

RESULTS

In 2019, there were 34.1 million (95% UI 31.7-36.8) incident cases of LRIs in MENA, with an age-standardised rate of 6510.2 (95% UI 6063.6-6997.8) per 100,000 population. The number of regional DALYs was 4.7 million (95% UI 3.9-5.4), with an age-standardised rate of 888.5 (95% UI 761.1-1019.9) per 100,000 population, which has decreased since 1990. Furthermore, Egypt [8150.8 (95% UI 7535.8-8783.5)] and Afghanistan [61.9 (95% UI 52.1-72.6)] had the highest age-standardised incidence and death rates, respectively. In 2019, the regional incidence and DALY rates were highest in the 1-4 age group, in both females and males. In terms of deaths, pneumococcus and H. influenza type B were the most and least common types of LRIs, respectively. From 1990 to 2019, the burden of LRIs generally decreased with increasing SDI. There were significant positive correlations between SDI and the AAPCs for the age-standardised incidence, death and DALY rates (p < 0.05). Over the 1990-2019 period, the regional incidence, deaths and DALYs attributable to LRIs decreased with AAPCs of - 1.19% (- 1.25 to - 1.13), - 2.47% (- 2.65 to - 2.28) and - 4.21% (- 4.43 to - 3.99), respectively.

CONCLUSIONS

The LRI-associated burden in the MENA region decreased between 1990 and 2019. SDI had a significant positive correlation with the AAPC and pneumococcus was the most common underlying cause of LRIs. Afghanistan, Yemen and Egypt had the largest burdens in 2019. Further studies are needed to investigate the effectiveness of healthcare interventions and programs to control LRIs and their risk factors.

Risk factors for disease severity and increased medical resource utilization in respiratory syncytial virus (+) hospitalized children: A descriptive study conducted in four Belgian hospitals

Background

We aimed to provide regional data on clinical symptoms, medical resource utilization (MRU), and risk factors for increased MRU in hospitalized respiratory syncytial virus (RSV)-infected Belgian pediatric population.

Methods

This prospective, multicenter study enrolled RSV (+) hospitalized children (aged ≤5y) during the 2013–2015 RSV seasons. RSV was diagnosed within 24h of hospitalization. Disease severity of RSV (+) patients was assessed until discharge or up to maximum six days using a Physical Examination Score (PES) and a derived score based on ability to feed, dyspnea and respiratory effort (PES3). MRU (concomitant medications, length of hospitalization [LOH], and oxygen supplementation) was evaluated. Kaplan-Meier survival analysis was performed to compare MRU by age and presence of risk factors for severe disease. Association between baseline covariates and MRU was analyzed using Cox regression models.

Results

In total, 75 children were included, Median (range) age was 4 (0–41) months, risk factors were present in 18.7%, and early hospitalization (≤3 days of symptom onset) was observed in 57.3% of patients. Cough (100%), feeding problems (82.2%), nasal discharge (87.8%), and rales and rhonchi (82.2%) were frequently observed. Median (range) LOH and oxygen supplementation was 5 (2–7) and 3 (1–7) days. Oxygen supplementation, bronchodilators, and antibiotics were administered to 58.7%, 64.0%, and 41.3% of the patients, respectively. Age <3 months and baseline total PES3 score were associated with probability and the duration of receiving oxygen supplementation. LOH was not associated with any covariate.

Conclusion

RSV is associated with high disease burden and MRU in hospitalized children. Oxygen supplementation but not length of hospitalization was associated with very young age and the PES3 score. These results warrant further assessment of the PES3 score as a predictor for the probability of receiving and length of oxygen supplementation in RSV hospitalized children.

Registration

NCT02133092

Association Between Respiratory Syncytial Virus-Associated Acute Lower Respiratory Infection in Early Life and Recurrent Wheeze and Asthma in Later Childhood

BACKGROUND

Recurrent wheeze and asthma in childhood are commons causes of chronic respiratory morbidity globally. We aimed to explore the association between respiratory syncytial virus (RSV) infection in early life and subsequent respiratory sequelae up to age 12 years.

METHODS

We estimated the strength of association by 3 control groups and 3 follow-up age groups, with data from studies published between January 1995 and May 2018. We also estimated associations by diagnostic criteria, age at infection, and high-risk population.

RESULTS

Overall, we included 41 studies. A statistically significant association was observed between early life RSV infection and subsequent childhood recurrent wheeze, in comparison to those who were healthy or those without respiratory symptoms: OR 3.05 (95% confidence interval [CI], 2.50-3.71) for 0 to <36 months follow-up age; OR 2.60 (95% CI, 1.67-4.04) for 36-72 months; and OR 2.14 (95% CI, 1.33-3.45) for 73-144 months. For the subsequent development of asthma, a statistically significant association was observed only in relation to those aged 73-144 months at follow-up: OR 2.95 (95% CI, 1.96-4.46).

CONCLUSIONS

Further studies using standardized definitions and from diverse settings are needed to elucidate the role of confounders and provide more robust estimates.

Live-attenuated Vaccines Prevent Respiratory Syncytial Virus-associated Illness in Young Children

Rationale: Active immunization is needed to protect infants and young children against respiratory syncytial virus (RSV). Rationally designed live-attenuated RSV vaccines are in clinical development.Objectives: Develop preliminary estimates of vaccine efficacy, assess durability of antibody responses to vaccination and "booster" responses after natural RSV infection, and determine sample sizes needed for more precise estimates of vaccine efficacy.Methods: We analyzed data from seven phase 1 trials of live-attenuated RSV vaccines in 6- to 24-month-old children (n = 239).Measurements and Main Results: The five vaccine regimens that induced neutralizing antibody responses in ≥80% of vaccinees (defined post hoc as "more promising") protected against RSV-associated medically attended acute respiratory illness (RSV-MAARI) and medically attended acute lower respiratory illness (RSV-MAALRI) and primed for potent anamnestic responses upon natural exposure to wild-type RSV. Among recipients of "more promising" RSV vaccines, efficacy against RSV-MAARI was 67% (95% confidence interval [CI], 24 to 85; P = 0.008) and against RSV-MAALRI was 88% (95% CI, -9 to 99; P = 0.04). A greater than or equal to fourfold increase in RSV serum neutralizing antibody following vaccination was strongly associated with protection against RSV-MAARI (odds ratio, 0.26; 95% CI, 0.09 to 0.75; P = 0.014) and RSV-MAALRI; no child with a greater than or equal to fourfold increase developed RSV-MAALRI. Rates of RSV-MAARI and RSV-MAALRI in placebo recipients were 21% and 7%, respectively. Given these rates, a study of 540 RSV-naive children would have 90% power to demonstrate ≥55% efficacy against RSV-MAARI and ≥80% efficacy against RSV-MAALRI; if rates were 10% and 3%, a study of 1,300 RSV-naive children would be needed.Conclusions: Rapid development of a live-attenuated RSV vaccine could contribute substantially to reducing the global burden of RSV disease.

Airway gene-expression classifiers for respiratory syncytial virus (RSV) disease severity in infants

BACKGROUND

A substantial number of infants infected with RSV develop severe symptoms requiring hospitalization. We currently lack accurate biomarkers that are associated with severe illness.

METHOD

We defined airway gene expression profiles based on RNA sequencing from nasal brush samples from 106 full-tem previously healthy RSV infected subjects during acute infection (day 1-10 of illness) and convalescence stage (day 28 of illness). All subjects were assigned a clinical illness severity score (GRSS). Using AIC-based model selection, we built a sparse linear correlate of GRSS based on 41 genes (NGSS1). We also built an alternate model based upon 13 genes associated with severe infection acutely but displaying stable expression over time (NGSS2).

RESULTS

NGSS1 is strongly correlated with the disease severity, demonstrating a naïve correlation (ρ) of ρ = 0.935 and cross-validated correlation of 0.813. As a binary classifier (mild versus severe), NGSS1 correctly classifies disease severity in 89.6% of the subjects following cross-validation. NGSS2 has slightly less, but comparable, accuracy with a cross-validated correlation of 0.741 and classification accuracy of 84.0%.

CONCLUSION

Airway gene expression patterns, obtained following a minimally-invasive procedure, have potential utility for development of clinically useful biomarkers that correlate with disease severity in primary RSV infection.

Economic-Burden Trajectories in Commercially Insured US Infants With Respiratory Syncytial Virus Infection

BACKGROUND

This study evaluates the long-term respiratory syncytial virus (RSV) burden among preterm and full-term infants in the United States.

METHODS

Infants with birth hospitalization claims and ≥24 months of continuous enrollment were retrospectively identified in the Truven MarketScan Commercial Claims and Encounters database for the period 1 January 2004-30 September 2015. Infants with RSV infection in the first year of life (n = 38 473) were matched to controls (n = 76 825), and remaining imbalances in the number of individuals in each group were adjusted using propensity score methods. All-cause, respiratory-related, and asthma/wheezing-related 5-year average cumulative costs were measured.

RESULTS

Early premature (n = 213), premature (n = 397), late premature (n = 4446), and full-term (n = 33 417) RSV-infected infants were matched to 424, 791, 8875, and 66 735 controls, respectively. After 2 years since RSV diagnosis, all-cause cumulative costs for RSV-infected infants as compared to those for controls increased by $22 081 (95% confidence interval [CI], -$5800-$42 543) for early premature infants, by $14 034 (95% CI, $5095- $22 973) for premature infants, by $10 164 (95% CI, $8835-$11 493) for late premature infants, and by $5404 (95% CI, $5110-$5698) for full-term infants. The 5-year RSV burden increased to $39 490 (95% CI, $18 217-$60 764), $23 160 (95% CI, $13 002-$33 317),$13 755 (95% CI, $12 097-$15 414), and $6631 (95% CI, $6060-$7202), respectively. The RSV burden was higher when stratified by inpatient and outpatient setting and respiratory-related and asthma/wheezing-related costs.

CONCLUSIONS

The RSV burden extends across cost domains and prematurity, with the greatest burden incurred by the second year of follow-up. Findings are useful in determining the cost-effectiveness of RSV therapies in development.

Long-term Assessment of Healthcare Utilization 5 Years After Respiratory Syncytial Virus Infection in US Infants

BACKGROUND

Respiratory syncytial virus (RSV) is the primary cause of respiratory tract infections in infants; however, current burden estimates report only the short-term effects of acute infection.

METHODS

Infants with RSV infection and ≥24 months of continuous enrollment were retrospectively identified from the Truven MarketScan database (1 January 2004-30 September 2015). Exposed infants (n = 38 473) were propensity score matched to nonexposed controls (n = 76 825) by baseline characteristics and gestational age. Five-year cumulative all-cause, asthma/wheezing, and respiratory event-related hospitalization rates and physician and emergency department healthcare-resource utilization rates were assessed.

RESULTS

During follow-up, RSV-infected cohorts had higher average all-cause cumulative hospitalization rates, compared with controls, with values of 79.9 hospitalizations/100 patient-years (95% confidence interval [CI], 41.7-118.2) for 213 early premature infants (P < .001), 18.2 hospitalizations/100 patient-years (95% CI, .8-35.7) for 397 premature infants (P = .04), 34.2 hospitalizations/100 patient-years (95% CI, 29.1-39.2) for 4446 late premature infants (P < .001), and 16.1 hospitalizations/100 patient-years (95% CI, 14.9-17.4) for 33 417 full-term infants (P < .001). Cumulative rates of physician and emergency department visits were also higher for RSV-infected infants. Asthma/wheezing accounted for 10%-18% of total 5-year physician visits.

CONCLUSIONS

Infant RSV infection has a significant long-term healthcare-resource utilization impact across gestational ages for at least 5 years after infection, most of it in the first 2 years. Systematically collecting healthcare-resource utilization data will be important for cost-effectiveness evaluations of RSV interventions in planned or ongoing trials.

Early-life respiratory syncytial virus lower respiratory tract infection in a South African birth cohort: epidemiology and effect on lung health

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection (LRTI) in children. Early-life RSV LRTI might affect long-term health but there are few data from low-income and middle-income countries. We investigated the epidemiology and effect of early-life RSV LRTI on lung health in a South African birth cohort.

METHODS

We conducted the Drakenstein Child Health Study (DCHS), an ongoing birth cohort longitudinal study in the Western Cape province, South Africa. We enrolled pregnant women aged 18 years or older during their second trimester of pregnancy at two public health clinics. We followed up study children from birth to 2 years. The primary outcome of the study was LRTI and RSV LRTI. LRTI and wheezing episodes were identified through active surveillance; respiratory samples were tested for RSV and other pathogens. Wheezing was longitudinally identified by caregiver report and ascertainment at health facilities. Lung function was measured from 6 weeks to 2 years. We analysed the associations between RSV LRTI and subsequent LRTI, wheezing, and lung function using generalised estimating equations and mixed-effects linear regression.

FINDINGS

We enrolled 1137 mothers between March 5, 2012, and March 31, 2015. Among their 1143 infants, accruing 2093 child-years of follow-up, there were 851 cases of LRTI (incidence 0·41 episodes per child-year, 95% CI 0·38-0·43). Admission to hospital owing to LRTI occurred in 169 (20%) cases (incidence 0·08 episodes per child-year, 0·07-0·09), with a case-fatality ratio of 0·5%. RSV was detected in 164 (21%) of 785 LRTI events with a specimen available for qPCR, an incidence of 0·08 episodes per child-year (0·07-0·09); highest at age 0-6 months (0·15 episodes per child-year, 0·12-0·19). Children with a first RSV LRTI were three times as likely to develop recurrent LRTI compared with those with non-RSV LRTI (0·32 [0·22-0·48] vs 0·10 [0·07- 0·16] episodes per child-year; p<0·0001), particularly following hospitalised RSV LRTI. RSV LRTI and hospitalisation for all-cause LRTI were independently associated with recurrent wheezing (adjusted incident rate ratio 1·41, 95% CI 1·25-1·59, for RSV LRTI and 1·48, 1·30-1·68, for hospitalisation). LRTI or recurrent LRTI was associated with impaired lung function, but a similar outcome was observed following RSV LRTI or non-RSV LRTI. All-cause LRTI was associated with an average 3% higher respiratory rate (95% CI 0·01-0·06; p=0·013) and lower compliance (-0·1, -0·18 to 0·02) at 2 years compared with no LRTI. Recurrent LRTI was associated with further increased respiratory rate (0·01, 0·001-0·02), resistance (0·77 hPa s L-1, 0·07-1·47), and lower compliance (-0·6 mL hPa-1, -0·09 to -0·02) with each additional event.

INTERPRETATION

RSV LRTI was common in young infants and associated with recurrent LRTI, particularly after hospitalised RSV. Hospitalisation for all-cause LRTI, especially for RSV-LRTI, was associated with recurrent wheezing. Impairments in lung function followed LRTI or recurrent episodes, but were not specific to RSV. New preventive strategies for RSV might have an effect on long-term lung health.

FUNDING

Bill & Melinda Gates Foundation; South African Medical Research Council; National Research Foundation South Africa; National Institutes of Health, Human Heredity and Health in Africa; Wellcome Trust.

Nebulised ALX-0171 for respiratory syncytial virus lower respiratory tract infection in hospitalised children: a double-blind, randomised, placebo-controlled, phase 2b trial

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of severe lower respiratory tract infection, with a high global health burden. There are no effective treatments available. ALX-0171 is a novel trivalent Nanobody with antiviral properties against RSV. We aimed to assess the safety and antiviral activity of nebulised ALX-0171 in children admitted to hospital with RSV lower respiratory tract infection.

METHODS

This double-blind, randomised, placebo-controlled, phase 2b trial was done in 50 hospital paediatric departments across 16 countries. Previously healthy children aged between 28 days to younger than 24 months who were admitted to hospital with RSV acute severe lower respiratory tract infection were randomly assigned in three sequential safety cohorts (3:1) to receive nebulised ALX-0171 (cohort 1 received 3 mg/kg, cohort 2 received 6 mg/kg, and cohort 3 received 9 mg/kg) or placebo once daily for 3 days using web-based randomisation in the sequential safety part (first block size 12, subsequently four). In a parallel part of the study, participants (cohort 4) were randomly assigned (parallel 1:1:1:1) to receive nebulised ALX-0171 3 mg/kg, 6 mg/kg, 9 mg/kg, or placebo (blocks of eight by restricted randomisation). Study drug masking was by two consecutive nebulisations (each either ALX-0171 or placebo) depending on assigned treatment group. The primary outcome was to evaluate time for the RSV viral load to drop to below quantifiable limit, measured by plaque assay on mid-turbinate nasal swabs. Safety, clinical efficacy, pharmacokinetics, viral load by RT-qPCR, and immunogenicity were secondary outcomes. Analysis, including of the primary outcome, was by modified intention to treat (participants receiving at least one dose of study drug as assigned), and safety was assessed in all children who received at least one administration of study drug, as treated. This trial is registered with EudraCT, 2016-001651-49.

FINDINGS

Between Jan 10, 2017, and April 26, 2018, 175 children (median age 4·8 months [IQR 2·0-10·8]), received at least one dose of study drug (45 received 3 mg/kg of ALX-0171, 43 received 6 mg/kg of ALX-0171, 45 received 9 mg/kg of ALX-0171, and 42 received placebo; the modified intention-to-treat population) commencing at a mean 3·3 days (SD 1·1) from symptom onset. Median time for the viral load to drop to below quantifiable limit on plaque assay was significantly faster for the 3 mg/kg group (median 14·2 h [IQR 5·0-28·0]), 6 mg/kg group (5·1 h [4·7-28·5]), and 9 mg/kg group (5·1 h [4·6-5·9]) than the placebo group (46·1 h [25·2-116·7]; hazard ratio [HR] all ALX-0171 groups vs placebo 2·6 [1·7-3·9]; p<0·0001). Median time for the viral load to drop below quantification limit with RT-qPCR was 95·9 h (IQR 26·7 to not estimable) for the placebo group (n=35) versus 49·4 h (25·1 to 351·4) for all ALX-0171 groups (n=118). Clinical outcomes were not improved by ALX-0171 compared with placebo, with no difference in time to clinical response (oxygen saturation >92% for 4 h in room air and adequate oral feeding) in ALX-0171 groups and the placebo group (median 43·8 h [IQR 21·7-68·5] vs 47·9 h [22·5-76·4]; HR 1·1 [95% CI 0·8-1·6]) or change in the global severity score from baseline to 5 h post-dose on day 2 (-4 [IQR -6 to -2] vs -4 [-6 to -1]; difference in least-squares mean -0·45 [95% CI -1·39 to 0·49]). Serum concentrations of ALX-0171 on day 2 exceeded the concentration estimated to give full RSV neutralisation in the lung at 6 mg/kg and 9 mg/kg doses. Treatment-emergent antidrug antibodies were detected at day 14 in 46 (34%) of 135 patients who received ALX-0171 and ten (26%) of 39 patients who received placebo. Serious adverse events were reported in five (13%) of 40 children in the placebo group and ten (7%) of 135 children in all ALX-0171 groups, leading to study drug discontinuation in three children (two in the 3 mg/kg group and one in the 6 mg/kg group). 13 of 15 serious adverse events (three of four in the 3 mg/kg group, two of three in the 6 mg/kg group, three of three in the 9 mg/kg group, and five of five in the placebo group) were related to worsening respiratory status, and none were considered to be related to the study drug.

INTERPRETATION

Antivirals against RSV might be unable to improve clinical course once RSV lower respiratory tract infection is established. Future studies of RSV antivirals should focus on earlier intervention and more precise measurement of objective outcomes before the onset of significant lower respiratory tract inflammation.

FUNDING

Ablynx, a Sanofi Company.

Assessing the strength of evidence for a causal effect of respiratory syncytial virus lower respiratory tract infections on subsequent wheezing illness: a systematic review and meta-analysis

Background

Although a positive association has been established, it is unclear whether lower respiratory tract infections (LRTIs) with respiratory syncytial virus (RSV) cause chronic wheezing illnesses. If RSV-LRTI were causal, we would expect RSV-LRTI prevention to reduce the incidence of chronic wheezing illnesses in addition to reducing acute disease. We aimed to evaluate the strength of evidence for a causal effect of RSV-LRTI on subsequent chronic wheezing illness to inform public health expectations for RSV vaccines.

Methods

We did a systematic review and meta-analysis of observational studies evaluating the association between RSV-LRTI and subsequent wheezing illness (exposure studies) and studies evaluating the association between RSV immunoprophylaxis and subsequent wheezing illness (immunoprophylaxis studies). Exposure studies were included if the exposure group members had an LRTI with laboratory-confirmed RSV and if the exposure ascertainment period began before 2 years of age and ended before 5 years of age. We required a wash-out period of more than 30 days between the index RSV-LRTI and the outcome measurement to allow for resolution of the acute illness. Comparisons between RSV-LRTI and non-RSV-LRTI were not included. Immunoprophylaxis studies were included if they measured the association with subsequent wheezing illness relative to a control group, either in a randomised controlled trial (RCT) or an observational design. For the immunoprophylaxis drugs in question, we required evidence of efficacy in targeting RSV-LRTI from at least one RCT to ensure biological plausibility. All variations of wheezing illness were combined into a single outcome that refers broadly to asthma or any other respiratory illness with wheezing symptoms. Ovid MEDLINE and Embase databases were searched from inception up to Aug 28, 2018. We evaluated whether data from exposure studies could provide evidence against the most viable non-causal theory that RSV-LRTI is a marker of respiratory illness susceptibility rather than a causal factor. Additionally, we tested whether RSV immunoprophylaxis reduces the odds of subsequent wheezing illnesses. We used a random-effects modelling framework and, to accommodate studies providing multiple correlated estimates, robust variance estimation meta-regressions. Meta-regression coefficients (b) quantify differences between exposure and comparator groups on the log_e odds ratio (log_e OR) scale.

Findings

From 14 235 records we identified 57 eligible articles that described 42 studies and provided 153 effect estimates. 35 studies estimated the direct effect of RSV-LRTI on wheezing illnesses (exposure studies) and eight evaluated the effect of RSV immunoprophylaxis (immunoprophylaxis studies). Exposure studies that adjusted for genetic influences yielded a smaller mean adjusted OR estimate (aOR₊ 2·45, 95% CI 1·23–4·88) compared with those that did not (4·17, 2·36–7·37), a significant difference (b 0·53, 95% CI 0·04–1·02). Infants who were not protected with RSV immunoprophylaxis tended to have higher odds of subsequent wheezing illness, as we would expect if RSV-LRTI were causal, but the effect was not significant (OR₊ 1·21, 95% CI 0·73–1·99). There was generally a high threat of confounding bias in the observational studies. Additionally, in both the observational studies and immunoprophylaxis RCTs, there was high risk of bias due to missing outcome data.

Interpretation

Our findings, limited to exposure and immunoprophylaxis studies, do not support basing policy decisions on an assumption that prevention of RSV-LRTI will reduce recurrent chronic wheezing illnesses.

Funding

Bill & Melinda Gates Foundation.

Single-Dose Nirsevimab for Prevention of RSV in Preterm Infants

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants, and a need exists for prevention of RSV in healthy infants. Nirsevimab is a monoclonal antibody with an extended half-life that is being developed to protect infants for an entire RSV season with a single intramuscular dose.

METHODS

In this trial conducted in both northern and southern hemispheres, we evaluated nirsevimab for the prevention of RSV-associated lower respiratory tract infection in healthy infants who had been born preterm (29 weeks 0 days to 34 weeks 6 days of gestation). We randomly assigned the infants in a 2:1 ratio to receive nirsevimab, at a dose of 50 mg in a single intramuscular injection, or placebo at the start of an RSV season. The primary end point was medically attended RSV-associated lower respiratory tract infection through 150 days after administration of the dose. The secondary efficacy end point was hospitalization for RSV-associated lower respiratory tract infection through 150 days after administration of the dose.

RESULTS

From November 2016 through November 2017, a total of 1453 infants were randomly assigned to receive nirsevimab (969 infants) or placebo (484 infants) at the start of the RSV season. The incidence of medically attended RSV-associated lower respiratory tract infection was 70.1% lower (95% confidence interval [CI], 52.3 to 81.2) with nirsevimab prophylaxis than with placebo (2.6% [25 infants] vs. 9.5% [46 infants]; P<0.001) and the incidence of hospitalization for RSV-associated lower respiratory tract infection was 78.4% lower (95% CI, 51.9 to 90.3) with nirsevimab than with placebo (0.8% [8 infants] vs. 4.1% [20 infants]; P<0.001). These differences were consistent throughout the 150-day period after the dose was administered and across geographic locations and RSV subtypes. Adverse events were similar in the two trial groups, with no notable hypersensitivity reactions.

CONCLUSIONS

A single injection of nirsevimab resulted in fewer medically attended RSV-associated lower respiratory tract infections and hospitalizations than placebo throughout the RSV season in healthy preterm infants. (Funded by AstraZeneca and Sanofi Pasteur; ClinicalTrials.gov number, NCT02878330.).

Informing randomized clinical trials of respiratory syncytial virus vaccination during pregnancy to prevent recurrent childhood wheezing: A sample size analysis

BACKGROUND

Early RSV illness is associated with wheeze-associated disorders in childhood. Candidate respiratory syncytial virus (RSV) vaccines may prevent acute RSV illness in infants. We investigated the feasibility of maternal RSV vaccine trials to demonstrate reductions in recurrent childhood wheezing in general paediatric populations.

METHODS

We calculated vaccine trial effect sizes that depended on vaccine efficacy, allocation ratio, rate of early severe RSV illness, risk of recurrent wheezing at age 3, and increased risk of RSV infection on recurrent wheezing. Model inputs came from systematic reviews and meta-analyses. For each combination of inputs, we estimated the sample size required to detect the effect of vaccination on recurrent wheezing.

RESULTS

There were 81 scenarios with 1:1 allocation ratio. Risk ratios between vaccination and recurrent wheezing ranged from 0.9 to 1.0 for 70% of the scenarios. Among the 57 more plausible scenarios, the lowest sample size required to detect significant reductions in recurrent wheezing was 6196 mother-infant pairs per trial arm; however, 75% and 47% of plausible scenarios required >31,060 and >100,000 mother-infant pairs per trial arm, respectively. Studies with asthma endpoints at age 5 will likely need to be larger.

DISCUSSION

Clinical efficacy trials of candidate maternal RSV vaccines undertaken for licensure are unlikely to demonstrate an effect on recurrent wheezing illness due to the large sample sizes likely needed to demonstrate a significant effect. Further efforts are needed to plan for alternative study designs to estimate the impact of maternal RSV vaccine programs on recurrent childhood wheezing in general populations.

Maternal immunisation: What have been the gains? Where are the gaps? What does the future hold?

The vaccination of pregnant women has enormous potential to protect not only mothers from vaccine-preventable diseases but also their infants through the passive acquisition of protective antibodies before they are able to themselves acquire protection through active childhood immunisations. Maternal tetanus programmes have been in place since 1989, and as of March 2018, only 14 countries in the world were still to reach maternal neonatal tetanus elimination status. This has saved hundreds of thousands of lives. Building on this success, influenza- and pertussis-containing vaccines have been recommended for pregnant women and introduced into immunisation programmes, albeit predominantly in resource-rich settings. These have highlighted some important challenges when additional immunisations are introduced into the antenatal context. With new vaccine candidates, such as respiratory syncytial virus (RSV) and group B streptococcus (GBS), on the horizon, it is important that we learn from these experiences, identify the information gaps, and close these to ensure safe and successful implementation of maternal vaccines in the future, particularly in low- and middle-income countries with a high burden of disease.