COVID-19 generally appear after 2 to 14 days of exposure to the virus whereas patients can experience the symptoms of Flu in about 1 to 4 days post-exposure.
As both illnesses are spread through droplets i.e. when an infected person talks, coughs, or sneezes in close quarters to an uninfected person, the prevention techniques are also quite similar.
To prevent the spread of Covid-19 and the Flu, it is advised for patients to practice good hand hygiene, encourage masking, and avoid close contact with infected individuals while getting vaccinated for both illnesses.
Given that the COVID-19 virus is distinct from the H3N2 virus that causes influenza, the vaccines used for each virus are different.