question: INTRODUCTION: Hospital-acquired infection with COVID-19 (HAI) has reduced from 14.3% to 4.2% over the last year, but substantial differences still exist between English NHS hospital trusts. METHODS: We assessed rates of HAI, comparing NHS hospital trusts using airborne respiratory protection (RPE, eg FFP3 masks) for all staff, as a marker of measures to reduce airborne spread, against those using mostly droplet precautions (eg surgical masks). Results/Discussion: RPE use was associated with a 33% reduction in HAI odds in the Delta wave, and 21% in the Alpha wave (p<0.00001). We recommend all hospitals make airborne mitigations a priority.