"Findings: Moderate-frequency handwashing predicted a lower personal risk of coronavirus infection (age-adjusted incidence rate ratio (aIRR) =0·65, p=0.03) although results for even higher levels of hand hygiene were not significant. For household index cases, overall practice of respiratory hygiene (aIRR =0·61, p=0.01) and handwashing after coughing or sneezing (aIRR = 0·35, p=0.02) were associated with lower risk of onwards transmission."
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3551360
