Childhood asthma is often preceded by recurrent episodes of troublesome lung symptoms in relation to airway infections in the first years of life.1, 2 Treatment of such episodes represents a major unmet clinical need; they are the most common cause of admission to hospital in young children, are a reason for stress and anxiety for families, and cause a major draw on health-care resources.3, 4, 5
We discovered in our birth cohort, the Copenhagen Prospective Studies on Asthma in Childhood 2000 (COPSAC2000; a previous birth cohort of children born to mothers with asthma), that airway bacteria (Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis) and respiratory viruses (at least one of picornavirus, respiratory syncytial virus, coronavirus, parainfluenzavirus, influenza virus, human metapneumovirus, adenovirus, or bocavirus) are equally closely associated with episodes of asthma-like symptoms in the first 3 years of life.6 Bacteria and viruses occurred together in most cases, challenging the previous hypothesis that episodes with asthma-like symptoms in this age group are largely virally induced.7, 8, 9 This finding suggested that bacteria might play an equal part in the pathogenesis of such episodes and that treatment with antibiotics might ameliorate symptoms. At present, guidelines do not recommend antibiotics for treatment of early asthma-like episodes,10 yet they are widely used.4 We did a randomised controlled trial (RCT) of azithromycin for treatment of episodes of troublesome lung symptoms in young children who were followed up prospectively in our new unselected Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC2010) birth cohort.11
Research in context
Study design and participants
In this randomised, double-blind, placebo-controlled trial, we recruited children from the COPSAC2010 cohort, which is a single-centre, population-based birth cohort of 700 children recruited from the general Danish population of Zealand, including Copenhagen, at 1 week of age and followed up prospectively at the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) research unit (Copenhagen and Naestved, Denmark) with deep clinical phenotyping.
Children aged 1–3 years diagnosed with recurrent asthma-like symptoms (troublesome lung symptoms) as defined in the Procedures section were eligible each time they had an episode of troublesome lung symptoms lasting at least 3 days. Exclusion criteria were macrolide allergy, heart, liver, neurological, and kidney disease, and, before each treatment, one or more clinical signs of pneumonia (respiratory frequency of 50 breaths per min or higher, fever of 39°C or higher, or C-reactive protein [CRP] concentration of 476·20 nmol/L [50 mg/L] or higher). Most mothers from the COPSAC2010 cohort also participated in other medical trials while pregnant and may have received dietary supplements or an influenza vaccination (NCT00856947, NCT00798226, and NCT01012557).
Additional details of baseline characteristics of the cohort are outlined in the COPSAC2010 cohort design report.
Randomisation and masking
Troublesome lung symptoms, consisting of cough, wheeze, or dyspnoea, severely affecting the wellbeing of the child, were monitored using daily diary cards filled out by the parents from birth.
We defined an episode as at least 3 consecutive days of troublesome lung symptoms, at which point we requested that the parents brought the child to the COPSAC research unit for an acute visit. We used the composite score of troublesome lung symptoms to describe asthma-like symptoms in the children, a score previously validated
and used in our clinical observational cohort studies of young children
and a randomised controlled trial.
At each acute visit, the diary cards were reviewed with the family by trained COPSAC paediatricians to validate symptom definitions and severity. Additionally, the research paediatrician did a thorough physical examination, consisting of assessment of fever, tachypnoea, chest recessions, wheezing, and lung and heart auscultation, and examination of the skin, ears, nose, and throat. Furthermore, we measured CRP concentration (detection limit of 76·19–1523·84 nmol/L [8–160 mg/L]) in the peripheral blood with the QuickRead 101 instrument (Orion Diagnostica, Espoo, Finland). We collected a hypopharyngeal aspirate using a soft suction catheter passed through the nose into the hypopharynx, as previously described.
We cultured the samples and isolated the airway bacterial pathogens H influenzae, S pneumoniae, and M catarrhalis. We obtained a nasopharyngeal aspirate for viral identification with PCR. The viral airway pathogens analysed were rhinoviruses, respiratory syncytial virus (RSV), and enteroviruses.
Recurrent troublesome lung symptoms were diagnosed if a child had: daily diary recordings of five episodes of troublesome lung symptoms within 6 months; 4 weeks of continuous symptoms; or a severe acute episode needing oral prednisolone or hospital admission. This diagnosis algorithm had previously been validated in our at-risk COPSAC2000 birth cohort.
At diagnosis of recurrent troublesome lung symptoms, we gave children a 3-month course of 2 × 50 μg fluticasone (Flixotide; GlaxoSmithKline, UK) inhaled from a pressurised metered dose inhaler delivered via a spacer twice daily. If a second relapse of troublesome lung symptoms occurred after cessation of inhaled corticosteroids, we initiated a 6-month course of inhaled corticosteroids.
We based our power calculations on the duration of episodes of troublesome lung symptoms at age 1–3 years in the children of the previous COPSAC2000 cohort.
86 independent episodes were needed to detect a difference of 1 day duration of episodes with a power of 90%, a p value of 0·05, and an SD of the duration of an episode of 1·4 days.
Role of the funding source
207 (30%) of the 700 children enrolled in the main cohort were diagnosed with recurrent troublesome lung symptoms during the first 3 years of life; between Nov 17, 2010, and Jan 28, 2014, we randomly allocated 158 episodes for trial treatment (79 [50%] to azithromycin and 79 [50%] to placebo; figure 1) from 72 (35%) of these children. Before analyses, we excluded ten (6%) episodes from the analysis (five [6%] in each group), nine (6%) because of missing diary information (azithromycin four [5%]; placebo five [6%]) and one (1%; in azithromycin group) because the treatment was never given to the child.
|RCT participants (n=72)||Non-RCT participants (n=135)|
|Male sex||47 (65%)||74 (55%)|
|White||70 (97%)||130 (96%)|
|Older children in the home at birth||39 (54%)||70 (52%)|
|Sensitisation (SPT or specific IgE)||8 (11%)||20 (15%)|
|Atopic dermatitis||21 (30%)||39 (30%)|
|17q21 risk variant (RS2305480)||26 (41%)||46 (39%)|
|Smoking in pregnancy||9 (13%)||16 (12%)|
|Cat or dog at birth||26 (36%)||48 (36%)|
|Antibiotics in pregnancy||31 (43%)||50 (37%)|
|Term birth >37 weeks||67 (93%)||127 (94%)|
|Caesarean section||18 (25%)||31 (23%)|
|Season of birth|
|Winter||25 (35%)||38 (28%)|
|Spring||17 (24%)||37 (27%)|
|Summer||12 (17%)||29 (21%)|
|Autumn||18 (25%)||31 (23%)|
|Maternal age at birth (years)||31·9 (4·7)||32·2 (4·5)|
|Maternal asthma||31 (44%)||38 (28%)|
|Maternal educational level|
|Low||9 (13%)||15 (11%)|
|Medium||53 (74%)||83 (61%)|
|High||10 (14%)||37 (27%)|
|Household annual income|
|Low||4 (6%)||17 (13%)|
|Medium||45 (63%)||73 (54%)|
|High||23 (32%)||45 (33%)|
|n (%)||Mean azithromycin episode duration (days)||Mean placebo episode duration (days)||% reduction (95% CI)||p value||Modification p value|
|All||148||3·4||7·7||63·3%(56·0 to 69·3)||<0·0001|
|C-reactive protein concentration (nmol/L)||133 (100%)||0·6350|
|≥76·19 nmol/L (≥8 mg/L)||23 (17%)||3·6||6·3||45·6% (−53·9 to 80·8)||0·2510|
|<76·19 nmol/L (<8 mg/L; lowest detection)||110 (83%)||3·5||8·4||59·4%(15·6 to 80·5)||0·0158|
|Fever (°C)||136 (100%)||0·4809|
|≥38||23 (17%)||3·8||4·9||21·4% (−61·6 to 61·8)||0·5122|
|<38||113 (83%)||3·6||7·2||47·3%(2·9 to 71·4)||0·0401|
|Objective wheeze||144 (100%)||0·8140|
|Yes||26 (18%)||3·4||8·8||55·0%(6·3 to 78·4)||0·0330|
|No||118 (82%)||3·6||13·0||60·1%(18·3 to 80·5)||0·0120|
|Any pathogenic bacteria||135 (100%)||0·2864|
|Present||90 (67%)||4·2||7·9||41·6% (−8·3 to 68·5)||0·0881|
|Not present||45 (33%)||2·0||5·5||64·7%(35·6 to 80·7)||0·0007|
|Haemophilus influenzae||135 (100%)||0·0323|
|Present||32 (24%)||2·7||12·1||77·0%(58·0 to 87·4)||<0·0001|
|Not present||103 (76%)||3·8||5·9||33·4% (−28·7 to 65·6)||0·2264|
|Moraxella catarrhalis||135 (100%)||0·9062|
|Present||64 (47%)||4·4||8·7||40·5% (−64·3 to 78·5)||0·3163|
|Not present||71 (53%)||2·8||5·2||45·0%(1·7 to 69·3)||0·0436|
|Streptococcus pneumoniae||135 (100%)||0·8576|
|Present||43 (32%)||3·3||6·2||44·4% (−22·1 to 74·7)||0·1436|
|Not present||92 (68%)||3·6||7·5||49·6%(3·8 to 73·5)||0·0377|
|Any pathogenic virus||135 (100%)||0·7999|
|Present||58 (43%)||3·8||6·8||44·0% (−32·4 to 76·4)||0·1866|
|Not present||77 (57%)||2·7||7·4||50·7%(27·3 to 66·6)||0·0004|
|Present||26 (19%)||4·6||6·9||26·7% (−172·6 to 80·3)||0·6430|
|Not present||109 (81%)||3·1||7·1||54·1% (34·3 to 67·9)||<0·0001|
|Present||22 (16%)||3·3||5·9||42·1% (−71·7 to 80·5)||0·3242|
|Not present||113 (84%)||3·6||7·2||46·9%(6·3 to 69·9)||0·0289|
|Present||27 (20%)||2·1||6·8||66·3%(31·5 to 83·4)||0·0026|
|Not present||108 (80%)||4·0||7·1||41·1% (−2·7 to 66·2)||0·0619|
This study is substantially strengthened by the prospective, longitudinal, daily diary recordings of lung symptoms before development of attacks, validated by study paediatricians at 6-monthly and acute visits. COPSAC served as the primary health-care centre for the birth cohort, ensuring a standardised approach to diagnosis and treatment, which improves reliability of diagnoses compared with reporting from community doctors and retrospective information from parents.
Diagnosis was based on an algorithm of symptom quantity, which has been analysed and validated in detail
and applied in our previous RCT
of inhaled corticosteroids in young children in the at-risk COPSAC2000 birth cohort. Such strict diagnostic procedure is paramount to clinical assessments, diagnoses, and treatments, which are otherwise poorly standardised in the community and more difficult in young children than later in life.
The in-depth clinical assessment of each respiratory episode by the study paediatrician before randomisation, including a thorough objective examination and CRP concentration measurement in the research clinic, ensured validity and homogeneity of the primary outcome and exclusion of children with clinical signs of pneumonia. This assessment minimised the possibility of the azithromycin effect being driven by treatment of bacterial pneumonia misclassified as an episode of asthma-like symptoms.
This study is the first, to our knowledge, to investigate and show an effect of azithromycin for treatment of acute respiratory episodes in young children with a history of recurrent asthma-like symptoms, in a cohort designed and powered to explore such effects. A third of all children will experience an episode of asthma-like symptoms in relation to airway infections before 3 years of age.
Shortening of such episodes by 63% is therefore clinically significant to the child, families, health-care user, and society. We noted that azithromycin had a marked effect in relation to any given type of episode independently of the trigger, clinical presentation, or symptom duration before the intervention, which suggests a broad application. The sensitivity analysis restricting episodes to the first randomisation validated the primary finding.
Asthma-like episodes in young children probably represent a heterogeneous clinical syndrome. Importantly, we excluded typical pneumonia based on predefined clinical criteria. Furthermore, most children (more than 80%) had undetectable concentrations of CRP and no fever at randomisation, and the treatment effect was similar in these children, strongly suggesting that the effect of azithromycin is not due to misclassification of pneumonia. Azithromycin treatment was particularly effective in children who were treated shortly after symptom debut. This finding makes us speculate that azithromycin is mainly acting on the acute inflammatory
processes related to exacerbations, rather than a persistent underlying inflammation. This hypothesis is supported by the absence of effect on time to next episode. Alternatively, azithromycin acts by clearing bacterial pathogens indirectly responsible for the respiratory episode through subsequent co-infection by a viral trigger, and therefore the treatment was more effective when initiated early in the episode than when initiated late.
This study is based on our previous birth cohort study
in which we discovered that pathogenic airway bacteria and respiratory viruses are equally closely associated with acute episodes of asthma-like symptoms in young children and mostly occur together. Our finding in this study that the treatment effect was strong, even in episodes for which no bacterial pathogen was detected, suggests that the effect of azithromycin is not only antibacterial. Macrolide antibiotics are active against both common airway pathogenic bacteria and atypical bacteria,
but also have anti-inflammatory activity
and, possibly, antiviral effects.
Studies of macrolides in adults with severe asthma episodes are ambiguous,
and macrolides reportedly reduce exacerbations in adults with an asthma type characterised by chronic neutrophilic inflammation.
Indeed, recurrent asthma-like symptoms in young children are also characterised by neutrophilic inflammation,
which, in particular, might be present for episodes triggered by H influenzae.
This corresponds with our finding of a stronger azithromycin effect in episodes triggered by H influenzae. Viral infection in general did not predict an altered effect of azithromycin treatment. Low numbers in some viral species groups limit the conclusions drawn about effect modification by specific viruses. Thus, the antibacterial, anti-inflammatory, and antiviral pathways of azithromycin could have contributed to the shortening of episode length observed in this study. We cannot rule out that the effects noted are mainly anti-inflammatory because episodes triggered by H influenzae induce neutrophilic inflammation
and azithromycin also reduced episode duration in children without any evidence of bacterial infection. An RCT
of treatment with azithromycin in RSV-positive children showed a reduction of the neutrophilic marker interleukin 8 at day 14 after azithromycin treatment. This finding could point towards an anti-inflammatory effect as the primary mediator of our findings and also explain why findings from previous RCTs
have failed to show treatment effects of non-anti-inflammatory antibiotics in acute exacerbations of childhood asthma.
Present guidelines do not recommend antibiotics for treatment of episodes of asthma-like symptoms in young children
and yet they are among the most commonly prescribed drugs for such episodes in both the USA and Europe.
Our data suggest an effect of azithromycin on acute asthma-like episodes and thereby identify a potential future treatment, but do not provide sufficient evidence to recommend this treatment in clinical practice. How the effect of azithromycin compares with narrow-spectrum antibiotics and whether any long-term effects are associated with recurrent use need to be investigated. We are keenly aware of the potential ecological issues relating to use of antibiotics in terms of bacterial ecology and resistance. Macrolide resistance in organisms causing respiratory illness in children is already an issue.
Future research should establish the choice of antimicrobial treatment and criteria for treatment, taking societal aspects into consideration. We did not identify strong effect modifiers from the objective clinical measures, concomitant treatments, or the microbiological profile other than the presence of H influenzae. Our data suggest that the effect increases by starting early in the episode. Future studies might help to identify specific disease phenotypes or biomarkers directing the treatment to specific groups of young children.
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