Communicable E58: Reducing hospital-acquired pneumonia – the HAPPEN trial and how it happened

In this episode of Communicable, Angela Huttner and Josh Davis are joined by Brett Mitchell, Aline Wolfensberger and Lauren Clack to discuss the HAPPEN trial to prevent hospital-acquired pneumonia led by Mitchell--and the important studies leading up to it [1-3]. The episode also explores trial designs used in their research that are both creative and practical, such as stepped-wedge and implementation trials, and how these approaches can bridge the gap between research and real-world practice.

References

1. Mitchell B, “The hospital acquired pneumonia prevention (HAPPEN) study: a multi-centre randomised controlled trial” in ESCMID Global 2026. https://online.escmid.org/media-6348-hospital-and-ventilator-associated-pneumonia-new-insights-on-prevention-diagnosis-and-treatment (Presentation).
2. White NM, et al. Effectiveness of oral care for the prevention of non-ventilator hospital-acquired pneumonia (HAPPEN): a multicentre, stepped-wedge, cluster-randomised trial in Australia. Lancet Infect Dis 2026. DOI: 10.1016/S1473-3099(26)00235-5.
3. Wolfensberger A, et al. Prevention of non-ventilator-associated hospital-acquired pneumonia in Switzerland: a type 2 hybrid effectiveness–implementation trial. Lancet Infect Dis 2023. DOI: 10.1016/S1473-3099(22)00812-X.

Further reading

• HAPPEN study website: Study overview and resources www.happenstudy.com
• Cassini A, et al. Burden of Six Healthcare-Associated Infections on European Population Health: Estimating Incidence-Based Disability-Adjusted Life Years through a Population Prevalence-Based Modelling Study. PLoS Med 2016. DOI:  10.1371/journal.pmed.1002150. 
• Pronovost P, et al. An Intervention to Decrease Catheter-Related Bloodstream Infections in the ICU. NEJM. DOI: 10.1056/NEJMoa061115. 
• Bion J, et al. ‘Matching Michigan’: a 2-year stepped interventional programme to minimise central venous catheter-blood stream infections in intensive care units in England. BMJ Quality & Safety 2013. DOI: 10.1136/bmjqs-2012-001325.
• Dixon-Woods M, et al. Explaining Matching Michigan: an ethnographic study of a patient safety program. Implementation Sci 2013. DOI: 10.1186/1748-5908-8-70.  
• Clack L, et al. Hybrid effectiveness-implementation studies in infection prevention and infectious diseases: a narrative review. CMI 2025. DOI: 10.1016/j.cmi.2025.10.022.
• Hospital Acquired Pneumonia Prevention (HAPPEN) Study: Statistical Analysis Plan
  https://www.medrxiv.org/content/10.1101/2025.08.14.25333719v1
• Oral care practices and hospital-acquired pneumonia prevention: A national survey of Australian nurses
  https://pubmed.ncbi.nlm.nih.gov/38724299/
• Nurses' experiences of providing oral care to hospitalised patients: A qualitative study
  https://pubmed.ncbi.nlm.nih.gov/40450434/