I have to agree with Michael. There's a reason Grandma's chicken soup with motzah balls is known as Jewish Penicillin. Of course, when fighting a bad cold, I admit to adding several drops of Tabasco sauce to increase the sinus opening qualities. Cajun Kosher, got to love it.
I love hot and sour soup, but it is just a a little too rich and thick for a cold fighting soup. If home made chicken is not available, my next choices would be a good bowl of rice noodle chicken or rare beef Pho, or Thai Tom Yum chicken soup.