Once the "flu" is well advanced, the remedy won't work anymore. In that case one needs the advice of an experienced classical homeopath to find the remedy which corresponds to the totality of symptoms. That advice can get expensive, whereas Oscillococcinum is inexpensive. It is recommended that during the winter months one takes a dose once a week as a preventive measure. Small children can take it too. I suggest it now to everyone I know. My daughter in law uses it successfully to treat her three small daughters (though she doesn't like to admit the value of any of my advice.)
Coffee antidotes the remedy for me, though not for my husband. Just to be on the safe side one should avoid camphor and toxic medications if possible while fighting off the virus.
I don't have any connection to the company. It amazes me to see all the advertisements for cold and flu "medications" when something like this is on the market. I always carry a tube in my purse just in case.