Hand hygiene compliance of healthcare workers before and during the COVID-19 pandemic: A long-term follow-up study

•Electronic hand hygiene systems are useful to assess the effects of interventions.•Hand hygiene levels significantly decrease over time once interventions are stopped.•Healthcare workers fall back into old hand hygiene routines quickly.•The COVID-19 pandemic does not necessarily improve hand hygiene levels.•Ongoing focus from the management is needed to ensure high hand hygiene levels.