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 trusts.

We assessed rates of HAI, comparing 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).

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.