Could mouthwash be effective against coronavirus?

Preliminary results from a study conducted by scientists at Cardiff University have indicated that some mouthwashes can eliminate coronavirus in saliva in 30 seconds.

The report states:

The ability of widely-available mouthwashes to inactivate SARS-CoV-2 in vitro was tested using a protocol capable of detecting a 5-log10 reduction in infectivity, under conditions mimicking the naso/oropharynx. During a 30 second exposure, two rinses containing cetylpyridinium chloride and a third with ethanol/ethyl lauroyl arginate eliminated live virus to EN14476 standards (>4-log10 reduction), while others with ethanol/essential oils and povidone-iodine (PVP-I) eliminated virus by 2-3-log10. Chlorhexidine or ethanol alone had little or no ability to inactivate virus in this assay. Studies are warranted to determine whether these formulations can inactivate virus in the human oropharynx in vivo, and whether this might impact transmission.

However, the scientists behind the study have cautioned against hailing mouthwash as a cure-all; the study has not been peer reviewed yet and there is no evidence that mouthwash can be used as a treatment for Covid-19, as it doesn't reach the respiratory tract or lungs.