Printing all lines between two strings, with one as a user input, using sed

I'm trying to use: sed -n '/String1/,/String2/p' Filename to print all lines between String1 and String2. Although I want to add String1 as a user input so, read $userinput sed -n '/$userinput/,/String2/p' Filename. But as the input is within quotation is is read as the string $userinput instead of the given input.