The clinical problem
Despite major advances in neonatal care, chronic lung disease—also called bronchopulmonary dysplasia (BPD)—remains a common complication of very preterm birth and can be associated with respiratory morbidity after discharge.
UK multicentre neonatal trial
AZTECAzithromycin Therapy for Chronic Lung Disease of Prematurity
A UK-wide clinical trial investigating whether azithromycin given soon after birth could improve outcomes for babies born very preterm.
799 babies recruited28 neonatal intensive care unitsRecruitment completeMain results published
Why AZTEC?
Protecting developing lungs after very preterm birth
Babies born before 30 weeks’ gestation are at high risk of chronic lung disease of prematurity because lung development is interrupted at a vulnerable stage. Respiratory support, inflammation and microorganisms including Ureaplasma may all contribute to lung injury.
The research question
AZTEC tested whether early azithromycin, an antibiotic with antimicrobial and anti-inflammatory effects, could improve survival without physiologically defined moderate or severe chronic lung disease.
The trial at a glance
A national randomised controlled trial
PopulationVery preterm infantsBabies born before 30 weeks’ gestation.
InterventionAzithromycinA 10-day course started soon after birth.
ComparatorPlaceboMatched placebo in a double-blind design.
Primary outcomeSurvival without CLDPhysiologically defined moderate/severe chronic lung disease.
UK collaboration
799 babies across 28 neonatal intensive care units
Recruitment finished in March 2022, above the original target of 796 infants, despite pauses and disruption during the COVID-19 pandemic. The published AZTEC-FU protocol describes recruitment from 28 tertiary neonatal units and approximately 77 step-down units across the UK, reflecting the scale of the national collaboration.
2019AZTEC beginsRecruitment opens across the UK.
2022Recruitment complete799 babies recruited.
2024Main RCT publishedResults appear in The Lancet Respiratory Medicine.
2025Investigators’ Study DayClinical, laboratory and follow-up findings presented.
2026Evidence expandsHTA and antimicrobial-resistance outputs continue.
AZTEC in animation
Watch the AZTEC results animation
A visual explanation of why the trial was undertaken, what treatment was tested and what the main trial found.
The video does not autoplay.
The programme continues
From neonatal intensive care to childhood lung health
AZTEC follow-up examines respiratory health, growth, development and safety beyond the neonatal admission. Together with BALLOON and RHiNO, it forms part of a broader programme following respiratory health from birth through childhood and beyond.
